Lightweight Roadrace Digest #31-40
LtWtRR-digest Sunday, June 29 1997 Volume 01 : Number 031
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Date: Fri, 27 Jun 1997 16:32:12 -0800
From: "Michael Moore"
Subject: LtWtRR Sears Point this Sunday
I'll be running a 250 Ducati at the AFM race this Sunday (if nothing
prevents it getting from Nevada to the Bay Area today) so anyone so
inclined please stop by and say hello. The bike will either have my
race number 364 on its fairing, or the owner's number if I run out of
time (but there shouldn't be too many full fairing equipped Ducati
singles there to sort through).
I'll also have some copies of John Bradley's book with me if you want
to take a first-hand look at it.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
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Date: Fri, 27 Jun 1997 17:46:05 -0800
From: "Michael Moore"
Subject: LtWtRR Some list stats and administrative hectoring
I thought I'd update everyone on the different lists' standing after
nearly 3 months of existance.
The current subscribers/list are:
97 Motorcycle Chassis Design
74 Vintage Roadrace
51 Vintage Dirt
32 Lightweight Roadrace
29 Suzuki GS Twins
This was prompted by several messages I've gotten over the last few
days wondering about the lack of traffic on some of the lists.
Well, we can't ALL be lurkers and expect to have anything to read on
the lists. The chassis list seems to chug along pretty steadily, but
some of the smaller lists have gone for 5 or 6 days recently without a
post. I try to post something if I notice a lack of traffic, but I
don't always have a ready list-related topic (nor do I always notice
the dearth of posts). Besides, even I'm not going to believe you ALL
signed on to the lists just to read my posts (certainly no more than
60% will fall into this category).
I started these lists because 1) I'm interested in the topics and
wasn't seeing enough related posts on the 11 other lists that I'm on,
and 2) I thought there would be enough other people also interested in
these topics for me to justify $25/month to pay for the lists (yes, I
do have this streak of altruism that I've so far been unable to
eradicate).
As long as the lists generate enough traffic to keep me interested
I've got no problem with hosting the lists - after all it doesn't take
much for me to justify $5/month for a list since that's a pretty cheap
price for a month's entertainment.
The lists aren't taking much time to administer since I stopped
authorizing all sub/unsub actions, though I notice that every now and
again majordomo will pick somebody's sub/unsub to forward to me for
approval.
So write something now and then - even the small lists have enough
people for a post/day from a different person. I think it is safe to
presume that everyone knows how to type?!
I know I'm not the only one with a number of oddball projects, and I
wouldn't even mind hearing about some normal projects, if that isn't
an oxymoron.
The vintage lists have got about 60-70 years of history to draw on
(some of the roadrace stuff is also applicable to the lightweight-RR
list, so that list has got about 80-90 years to draw on), the chassis
design list doesn't seem to have any problems, and the GS list at
least has the benefit of current motorcycles, some of which should be
in near daily use. There are probably enough $200 GS-400s out there
that everyone on the other lists could go out and buy one in order to
justify joining the GS list and post to it.
PICTURES!!?? Would pictures of your list related bikes spark some
conversation? If I have to I'll set up a section for each list on the
web site to post list members bikes if you think that would start some
conversations going:
"Hey Vern, did you know that you've got an incorrect 25/59ths left
handed prawn nut on your bike? That was only offered on the Emile
Zola replica motoball bike produced in '06, and yours is the '07 Phil
Irving Repco special".
C'mon, c'mon, c'mon. You must have had some reason for joining the
lists - tell us about it.
Thanks to those who have been contributing on a steady basis - I'm
sure they'll be glad to carry the main load if the rest of you will
chime in now and again.
DIGESTS: Does anyone have a suggestion for an easy way that I can
make the old digests available, or is there any interest in this? I
suppose I could just save them with an .htm extension and use a set of
tags at top and bottom so they could be read off the web
site.
OK, the soapbox is now available for someone else - don't be shy.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
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Date: Sun, 29 Jun 1997 18:40:45 -0800
From: "Michael Moore"
Subject: LtWtRR Moore and Ducati Beat Kawasaki at Sears Point!
Well, at least I beat one Kawasaki, if not the whole field.
For my second race entry on the Harold Parks' 1966 250 Ducati race
bike (and I think Harold has raced this bike since new) I picked 250
SuperBike. Many of the 250 Production (internal mods OK, but stock
carbs/pipes) EX250 Kawasaki Ninjas and Honda VT250 Interceptors run up
into this class, and since the Duckling is eligible (a VERY stock
chassis) I thought it would be fun to see how I'd do against the
modern bikes.
I passed a few people off the starting grid (back row) and managed to
finish 16th of 17 starters (also beating the three who failed to
start). The Ducati was remarked on as the loudest bike on the track,
and a couple of friends in the race remarked that they weren't reeling
the 250 in on power so much as making up time in braking on the
corners (which I had to start WAY early with the stock SLS drum
brakes). I think this is probably the first 250 SuperBike finish in
an AFM race for a 250 Ducati in quite some time.
In the Vintage race(one row of 450cc and up bikes ahead of 2 rows of
sub-450cc bikes in a single wave start) I got a pretty decent start,
which was somewhat negated by being cut off in Turn 1, much of which I
made up by going around the outside in Turn 2. The 250 and 450
Production classes started before us in two waves, and we started
picking off back markers in the 250 Production class about half way
through the 8 lap race. The first two bikes in the small class were
250 Bultacos, and I came in third. The first place Bultaco finished
ahead of 3 big bikes, and 2nd place and I beat 2 of the bigger vintage
bikes.
Much fun was had by most, and it was entertaining to pass the modern
bikes.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
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End of LtWtRR-digest V1 #31
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LtWtRR-digest Wednesday, July 2 1997 Volume 01 : Number 032
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Date: Mon, 30 Jun 1997 20:46:46 -0800
From: "Michael Moore"
Subject: LtWtRR (Fwd) Re: 50cc racer
Here's a post from the VJMC list that I thought was worth sharing on
with you.
Cheers,
Michael
*****************************
- ------- Forwarded Message Follows -------
Date: Mon, 30 Jun 1997 19:19:39 -0700
From: joe broussard
Reply-to: suzukijo@ptw.com
Organization: Vintage Japanese MC
To: Johnmitzel@aol.com
Cc: vjmc@hyperreal.com
Subject: Re: (vjmc) 50cc racer
Johnmitzel@aol.com wrote:
>
> OK folks - I'm soliciting opinions from the "Peanut Gallery."
> I'm considering building a roadracer for a new 50cc class in the USCRA.
> Rules:
> Engine must have appeared prior to 1970. (Or have roots prior to then)
> No more than 4 speed tranny.
> I will not waste time beating life into anything Italian.
> What's the best choice?
You asked.
the Suzuki A-50 engine group, is an excellent choice.
I just finished a A-50 for my friend Mike berg, mikeberg@ix.netcom.com,
so you can email him for his opinion of how it runs.
this engine group was first sold in '67. its of the rotary valve group
and with an inner rotor magneto, and the RT kit, it feels like a RM 50.
to accomodate the 4 speed ruling you could use the beefier trans out of
the Tm 75 which was the same engine group, and of course its beefier
too, and only has 4 speeds. A, AC, AS, 50, TM, TS, 50 and 75 are all the
same engine group. Mix and match for the big carb and improved parts, as
you see fit.
I'm all sold out of RT kits though, so you are on your own. A50 and TS50
kits are similar, and will interchange. TS has the down pipe. A50
uppipe.
One could reproduce many of the improvements without the kit. Email me
if you want copies of the kit instructions.
with the kit alone, it put out 9.5 HP @ 10500 RPM! Peaky tho.
Joe.
------------------------------
Date: Tue, 1 Jul 1997 18:13:05 -0800
From: "Michael Moore"
Subject: LtWtRR re: Harold's 250
FYI when cleaning up Harold's 250 Ducati racer this afternoon I
noticed that it is running a 36mm carb. Not too shabby!
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
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Date: Wed, 2 Jul 1997 09:56:37 -0800
From: "Michael Moore"
Subject: LtWtRR Many more pictures
I just got my photos from Laguna Seca developed and from that roll of
film I've added:
8 detail photos of the Honda 250/6
2 detail photos of the MV 500/3
1 detail photo of the Benelli 350/4
2 detail photos of John Cronshaw's BSA Gold Star
1 photo of a Scott two-stroke race bike
1 photo of a Moto Parilla Gran Sport (with a Manx in the background)
The above are all on the graphics page, under either the Vintage
Japanese or Vintage Roadracer sections.
I've also added some more 125/150 Laverda thumpette pictures, both the
to the 150 Laverda page and duplicated in the Vintage Dirtbike section
of the graphics page.
On the "weighing the Laverda 750 racer" page I've added some photos of
the lightened fork caps, rear brake panel assy, and the frame assembly
including the swing arm, triple clamps and rear dampers.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
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End of LtWtRR-digest V1 #32
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LtWtRR-digest Saturday, July 5 1997 Volume 01 : Number 033
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Date: Thu, 3 Jul 1997 19:03:08 -0800
From: "Michael Moore"
Subject: LtWtRR Still more photos
The latest additions to the graphics page are:
about 10 different shots (mostly detail) of my friend Peter's Honda
CR77 road racer,
several photos of the mockup of my friend Larry's Husqvarna
125/Ducati 450 dirt bike,
two pictures of Harold Park's 1966 250 Ducati road racer (which I
raced last weekend),
and a couple of pictures on the Laverda weights page showing the stock
8mm steel valves and the new 7mm titanium valves (with bigger valve
heads).
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
------------------------------
Date: Fri, 4 Jul 1997 13:14:26 -0800
From: "Michael Moore"
Subject: LtWtRR Archived digests now available
I've just finished dumping the back digests into html documents and
putting them on the web site. You can find the links on the page that
previously held only the subscription information for the lists. I've
grouped the digests in batches of 10, and in spite of Julian's
pointing me in the direction of some PERL software that would grab the
digests and convert them, I just dumped them into html format with a
tag, so they aren't terribly pretty.
Now that I'm caught up it shouldn't be too much effort to add each
succeeding batch of 10 digests to the archives.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
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Date: Sat, 5 Jul 1997 10:49:01 -0800
From: "Michael Moore"
Subject: LtWtRR Tiny Tiddler Tyres
While looking at the Japanese Lump-Proof site I noticed a little
section mentioning that Bridgestone tire (at the urging of one of
their employees who used to race CR110s or something like that) has
made some small treaded race tires - 2.00x18F, 2.25x18R, and
2.50x18F&R.
I'm sure there are none of these currently available in the US, but
I've found that it is often possible to find a sympathetic ear with
some of the importers and get them to bring a small batch in (as I
did with the 2.75"x18" IRC tires).
There was also a little shot of a heavily developed CR110, where the
owner has made titanium exhaust pipe and clutch basket for the bike.
Ya gotta love these vintage race nutters.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
------------------------------
End of LtWtRR-digest V1 #33
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LtWtRR-digest Saturday, July 5 1997 Volume 01 : Number 034
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Date: Sat, 5 Jul 1997 13:58:08 -0800
From: "Michael Moore"
Subject: LtWtRR Making racing drum brakes
I've been thinking about racing drum brakes recently.
I've gotten some prices from the UK for replica Fontana/Seeley/Manx
etc brakes, and had to have a bit of a lie down to recover from
reading the prices.
How hard can it be to make a drum brake? Unfortunately, Phil
Irving's "Motorcycle Engineering" doesn't say anything about the
process.
I've got an Italian book called "La Moto Classica" which has an
article on classic Italian racing brakes, and I notice that Oldani
and MV appear to have shrunk the light-alloy drums onto the cast iron
friction surface, as the cast iron in these brakes is retained with
rivets. Fontana and Ceriani look to have cast the drum around the
friction material.
I have a veglia recollection from an old Motorcycle Weekly article on
the debut of the Eddie Robinson dual SLS brakes that were used by
Seeley that these wheels were actually two half-drum assys that were
then bolted or riveted together. This allowed Robinson to have the
inner drum surface (along the center plane of the wheel) taper out to
support the wheel bearing without the bother of fancy casting cores
in the center of a one-piece drum. Daniele Fontana of course just
had beautifully complex magnesium castings.
Eric Cheney threaded the inside of some of his aluminum drums and
the outside of the cast iron liner and screwed the two together,
possibly riveting them into place afterwards. I think with this he
did caution people not to run the brakes with the brake panel on the
opposite side of the wheel, as that would tend to unscrew the
drums/liners during use, instead of tightening them.
I don't know enough about the subject to be able to say if the same
cast iron used in a cylinder liner is suitable for a drum brake (and
I've been told that the dual SLS Grimeca drums as used on
Ducati/Morinis have a cast iron that is too soft in their drum liners
and are prone to rapid wear under racing use with racing friction
materials). It occurs to me that there must be some small car drums
of a suitable size that could be used as donors for a riveted-in
liner.
There are plenty of 2LS street drum brakes in junk yards that could
supply cams and lever assemblies. I haven't measured to see if 8"
Honda etc brake shoes are narrow enough to be doubled up and still
fit inside a typical vintage fork assy, and my Suzuki Wasser Buffle
brake is in my storage area and therefore not available to take
measurements.
(puff, puff) I take it back - I just ran down into the garage and
grabbed an 8" Super Hawk front drum. The backing plate adds approx
1.2" to the width of the brake hub (roughly 1.8" across the outside
of the spoke flanges), the shoes are 1.2" wide (the cast iron surface
is 1.4" wide), and drum ID is 7.87" (200mm). OA diameter is 9.74" (a
tight squeeze on my 10" lathe).
A doubled-up Superhawk brake would be about 5" across at the axle
(figuring 2 shoes at 1.2", 2 backing plates at 1.2", and another .25"
for a center aluminum wall). The brake shoes could be narrowed up to
make the O/A width of the brake narrower. I don't have a set of RR
35mm Ceriani forks handy to see what the width is inside the axle,
but I am running a Super Hawk brake in these forks on my CR216, with,
I think, a bit of spacer on each side of the wheel.
Starting with a nice 6061-T6 billet to make the drum would most
likely yield a stronger and longer-lived part than the typical
un-heat treated aluminum castings in all the street wheels. I don't
know if any of the specialist aluminum racing drum brakes were made
of anything like A356/357 (fairly common high-strength casting
alloys) then heat treated to a T6 or similar specification. My
aluminum reference book shows A356-T6 with a 33 ksi UT and 29 ksi
yield, and 6061-T6 with 45 ksi UT and 40 ksi yield (seems a
significant difference to me).
The drum would be a basic lathe operation (though with the spoke
flange my lathe would probably only accept an 8" ID drum size, darn),
with some rotary table work on the spoke holes afterwards.
Is a cast iron liner even needed? My 1974 Bultaco 350 Sherpa T had
a hard-chrome rubbing surface plated onto the inside of the drum.
There was apparently some problems with the original Spanish
hard-chrome, as I've read that Nigel Bowers (of NEB in the UK)
contracted to replate/regrind a big batch of the Bultaco hubs for
the UK importer, said hubs then holding up fine. Still, I wonder if
this could be sturdy enough for a road racing brake, though a drum
could probably be turned into scrap pretty quickly if the plating
wore through.
I'd be most interested to hear from those of you with the
appropriate engineering experience.
To maximize the input I'm posting this to the vintage-RR,
lightweight-RR and mc-chassis lists, so if you've got some cogent
comments you might want to cc: all the lists (and hopefully the
cross posting won't get out of control).
Be sure to save this post (if you are interested in the subject) as
I'm now going to include a bunch of comparitive drum brake sizes that
I compiled some years ago after much magazine thumbing. Keep in mind
that I didn't measure all of these brakes, just took the specs from
the data tables in the road tests.
If anyone has dimensions for a brake I've not listed, especially any
of the racing drum brakes, please let me know. I'll add that to the
list, and eventually put this up as a page on the web site.
Remember that it is not only the surface area of the friction swept
area that is important, but also the diameter at which the friction
is taking place. I guess you could multiply the friction area times
the radius of the friction area to come up with a brake effectiveness
coefficient (and I'm sure someone will correct me if I'm wrong here).
I'm not going to go back through and double check my surface area
calculations, so be prepared to recalculate if they look odd. The
square inches figure is the potential rubbing area on the drum, not
the actual square inches of the friction material.
I've put the nominal mm dimension after the bike name.
Suzuki drum brakes
GT550/750 (200mm)
7.81" OD x 1.0" wide (x 2), 49.07"**2 area, 191.6 coef
T500 (1967) (200mm)
8.0" x 1.6", 40.21"**2, 160.8 coef
T350 (1970) (180mm)
7.12" x 1.12", 25.06"**2, 89.21 coef
X-5 Invader (200cc) (160mm)
6.25" x 1.09", 21.4"**2, 66.87 coef
***********************************
Kawasaki drum brakes
H1R (250mm)
9.875" x .75" (x2), 46.53" **2, 229.74 coef
H1 (1969) (200mm)
7.9" x 1.4", 34.74" **2, 137.22 coef.
A7SS (180mm)
7.0" x 1.2", 26.38" **2, 92.33 coef.
***********************************
Yamaha drum brakes (someone measure their TD3 four shoe for me)
XS-650 (1969) (200mm)
7.8" x 1.3", 31.85" **2, 124.2 coef.
YDS-6 (1967) (180mm)
7.02" x 1.17", 25.8" **2, 90.3 coef.
***********************************
Honda drum brakes
CB350 (1970) (160mm)
6.3" x 1.4", 27.70" **2, 87.25 coef.
CB175 (1971) (160mm)
6.2" x 1.18", 22.98" **2, 71.24 coef.
CB77/ 1968 CB450 (200mm)
7.88" x 1.18", 29.21" **2, 115.08 coef.
***********************************
Bridgestone
350 GTR (190mm)
7.4" x 1.2", 27.89" **2, 103.2 coef.
175 (160mm)
6.2" x 1.18", 22.98" **2, 71.24 coef.
***********************************
Bultaco
250 Metralla (160mm)
6.3" x 1.6", 31.65" **2, 99.69 coef.
***********************************
Ducati 250 (180mm)
7.08 x ???
***********************************
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
------------------------------
End of LtWtRR-digest V1 #34
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LtWtRR-digest Sunday, July 6 1997 Volume 01 : Number 035
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Date: Sat, 5 Jul 1997 14:45:44 -0800
From: "Michael Moore"
Subject: LtWtRR More drum brake thoughts
I couldn't find a spec for A355/356 etc aluminum casting alloys in
the as-cast state (probably typical of production drums). If anyone
has that number so it can be compared to the T6 condition and to
6061-T6 I'd be curious to see how much lower. Along the same line,
if someone knows what alloy is likely to be used for the permanent
mold castings used in the Japanese drum brakes it would be
interesting to compare the specs for that in as cast condition to a
billet drum brake material.
Casting vs machining:
Making patterns gets expensive (my friend Peter was quoted $6-10K
for a pattern for his CR77 Honda cylinder), though a drum brake
should be a fairly simple pattern (as these things go). With the
widespread availability of CNC machining centers it might actually be
cheaper to have the hub and brake backing plates machined on a CNC
mill instead of cast and then machined. Plus, the parts could be
made of a strong aluminum billet which might allow them to be a bit
thinner/lighter than a cast (and hopefully heat treated) aluminum
part.
I suppose this would also hold true for magnesium. SAE 50 Mg casting
alloy in "heat treated and aged" is about 32K/16K UT/Y strength, and
SAE 511 ("used where high mechanical properties are required) is
about 39K/28K UT/Y strength. This is in comparison to the 6061-T6 at
45/40 UT/Y strength. I suppose someone would have to actually sit
down and calculate which material in the wrought form would provide
the best strength/stiffness/weight/cost mix. A billet aluminum
hub/plate assy might be able to be made nearly as light as a typical
cast magnesium unit, or a cast aluminum hub with Mg backing plates.
The cost of the patterns and finish machining would have to be
compared to writing the CNC program and having more scrap metal from
chewing the parts from billet. Interesting stuff, but I don't have
the knowledge to compare the two processes (strictly manual machine
tools in my garage at this time).
I know that Tony made lots of cast wheels, though I don't know if
they were all aluminum or if he did some magnesium wheels for the
race bikes as well. Maybe he'll be able to find some time to tell
us of the difference in weight/strength/cost between the materials.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
------------------------------
Date: Sat, 5 Jul 1997 15:13:55 -0800
From: "Michael Moore"
Subject: LtWtRR Drum brake web page up and running
You can find it off of the main page on the web site.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
------------------------------
Date: Sun, 6 Jul 1997 18:26:28 -0800
From: "Michael Moore"
Subject: LtWtRR Very many more pictures
My poor scanner is panting, it has been working so hard.
New additions to the graphics page are:
Road race:
Colin Lyster Lyntons, Manxes, G50s and 450 Hondas (with wings!)
The 500cc Phoenix two stroke twin
The 50cc Wooley/Yamaha two stroke single
A 50cc Sachs
A Mackintosh frame for a turbo Kawasaki road racer
A Difazio hub-steering AJS 7R
Action shots from two different Brands Hatch 500 mile production races
(Ducati and Suzuki 250s, Triumph/BSA 650s, Dunstall 750). One of the
pictures is a nice shot of Lance Weil.
A Fahron 125cc two-stroke single
The Ray Flack 350cc Manx kneeler (solo)
An early Rudi Kurth BMW kneeler
A MotoBi 250
Various racing drum brakes (on the drum brake page)
Dirt:
A Wasp MX sidecar
A Cheney Suzuki (the early twin-exhaust port 250 engine)
Some shots of a 175cc Honda twin trials bike
An action shot of Dave Bickers monowheeling
Engines:
An article on a 350cc Desmo single designed by Major John Treen in
1959.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
------------------------------
End of LtWtRR-digest V1 #35
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LtWtRR-digest Tuesday, July 8 1997 Volume 01 : Number 036
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Date: Mon, 7 Jul 1997 17:09:17 +1100
From: Daniel_Builth-Snoad@wlgore.com
Subject: LtWtRR Carb stack lengths
A question posed for the collective lurking genius out there:
How does carb stack length effect performance at different engine speeds?
A posting the other day referred to variable length inlet stacks which
changed with engine speed, assumably to boost mid-range. Does anyone out
there have knowledge of the theory behind this? I've always just treated
bellmouths as a given and you didn't mess with them too much. Particularly
with 2 strokes is there a great difference to be had using different intake
lengths?
This came up when I was talking to a friend who has just done a Yamma-Gamma
conversion (YPVS 350 motor into RG250 roller) and has had to ditch the
original airbox. By fitting pod filters he's lost some of the mid-range the
RZ had and we were thinking about how to find it again when the variable
inlet idea came up. The bike already has a servo mechanism dependent on RPM
so it wouldn't be such a huge step to piggyback telescopic trumpets off
this. Whilst the trick (read wank) factor is undeniable it'd be nice to
know if it had the potential for real gains before wading in with the
crowbar and chainsaw.
Thus the question is posed - can we get a better bike by playing with this
or have there been too many home-brews sacrificed in the garage for common
sense to prevail?
All feedback appreciated (I think)
Danny
------------------------------
Date: Tue, 8 Jul 1997 20:54:18 +0000
From: "Glenn Thomson"
Subject: Re: LtWtRR Carb stack lengths
On 7 Jul 97 at 17:09, Daniel_Builth-Snoad@wlgore.co wrote:
>
> How does carb stack length effect performance at different engine speeds?
> A posting the other day referred to variable length inlet stacks which
> changed with engine speed, assumably to boost mid-range. Does anyone out
> there have knowledge of the theory behind this? I've always just treated
> bellmouths as a given and you didn't mess with them too much. Particularly
> with 2 strokes is there a great difference to be had using different intake
> lengths?
>
> This came up when I was talking to a friend who has just done a Yamma-Gamma
> conversion (YPVS 350 motor into RG250 roller) and has had to ditch the
> original airbox. By fitting pod filters he's lost some of the mid-range the
> RZ had and we were thinking about how to find it again when the variable
> inlet idea came up. The bike already has a servo mechanism dependent on RPM
> so it wouldn't be such a huge step to piggyback telescopic trumpets off
> this. Whilst the trick (read wank) factor is undeniable it'd be nice to
> know if it had the potential for real gains before wading in with the
> crowbar and chainsaw.
Danny,
I'm curious about this myself. Net.lore has it that pulling the stacks
off the aircooled RDs leaves a hole in the midrange, but I don't believe
everything I read ( except here! ).
Did you come up with any answers?
Cheers
Glenn
msgr@hookup.net
Waterloo, Ontario, CANADA
------------------------------
End of LtWtRR-digest V1 #36
***************************
LtWtRR-digest Wednesday, July 16 1997 Volume 01 : Number 037
----------------------------------------------------------------------
Date: Tue, 8 Jul 1997 19:30:51 -0800
From: "Michael Moore"
Subject: Re: LtWtRR Carb stack lengths
> > bellmouths as a given and you didn't mess with them too much. Particularly
> > with 2 strokes is there a great difference to be had using different intake
> > lengths?
My limited understanding is that on two stroke road racers they
generally try for the shortest possible intake tract length. This
could easily prove to be 1978 technology though, so I'll defer to
more knowledgeable folks here.
However, 2 strokes should be subject to intake resonant lengths as
are four strokes, though they may want intake tracts of half the
length since they get an intake pulse from the engine twice as
frequently.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
------------------------------
Date: Wed, 09 Jul 1997 18:26:58 -0400
From: Bill
Subject: Re: LtWtRR Tiny Tiddler Tyres
Michael Moore wrote:
>
> While looking at the Japanese Lump-Proof site I noticed a little
> section mentioning that Bridgestone tire (at the urging of one of
> their employees who used to race CR110s or something like that) has
> made some small treaded race tires - 2.00x18F, 2.25x18R, and
> 2.50x18F&R.
I was just in Tokyo and brought back a set of Dunlop TT900GP
tires for an SRX250. They have lots of tiny bike tires available
there in much softer compounds than we get here.
I would recommend the BT39SS, a race version of the already soft
BT39 series. They have a narrow line but are targetted at 125cc
racing.
> I'm sure there are none of these currently available in the US, but
> I've found that it is often possible to find a sympathetic ear with
> some of the importers and get them to bring a small batch in (as I
> did with the 2.75"x18" IRC tires).
Yep, we couldn't find the bridgestones anywhere in the USA, the
distributor had never even heard of them. ;(
We decided to go with the dunlops after we got to Tokyo because they
were out of the sizes we needed in the BT39SS.
OTOH, I think the TT900GPs are the softest tires Ive even seen, the bike
is totally different now, Much recommended.
Bill
------------------------------
Date: Wed, 16 Jul 1997 19:46:10 -0400 (EDT)
From: SCOTTA336@aol.com
Subject: LtWtRR Oddball Spring Sources
Folks,
I've built a monstrosity of a Honda CR 80, big wheels & long swingarm & such.
The rear spring started life as something like a 2.8kg/mm. We cut about 1/4
of its coils off, reshaped & ground the ends like good boys, made a spacer to
make up the difference and ended up with 5.4 kg/mm. Seems like a big change,
since the formula for springs tells me the rate should vary as 1/n, with n
the number of active coils. Makes me suspect the scale we used.
In any case, whatever it is isn't enough. I can't cut any more coils out
without coilbind. I have a very similar ID spring for my WP shock for my
RS125 with a rate that works out to 6.2kg/mm (on the same scale). Again, not
enough length between extended and bound.
Paul Thede refused to honor my inquiry with a response, happy merely to say
it was impossible.
So, where do I go for custom springs? I know all the info that's necessary
for the spring guys to wind one, but don't know who to ask.
ScottA336@aol.com
------------------------------
End of LtWtRR-digest V1 #37
***************************
LtWtRR-digest Friday, July 18 1997 Volume 01 : Number 038
----------------------------------------------------------------------
Date: Wed, 16 Jul 1997 17:54:24 -0800
From: "Michael Moore"
Subject: LtWtRR Re: MC-Chassis Oddball Spring Sources
> So, where do I go for custom springs? I know all the info that's necessary
> for the spring guys to wind one, but don't know who to ask.
> ScottA336@aol.com
Hello Scott,
This is from the 12/95 Performance Racing Industry Buyers Guide
(race car stuff), so there may be some change in the phone numbers
due to different area code changes:
Eibach Springs (North America) 714-727-3700 Irvine CA
Coleman Machine Inc, Menominee WI 906-863-7883
Intrax Suspension Tech - Costa Mesa CA 714-549-5001
There are a number of off the shelf race car springs that will fit
common m/c dampers.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
------------------------------
Date: Wed, 16 Jul 1997 17:58:12 -0800
From: "Michael Moore"
Subject: LtWtRR Re: MC-Chassis Oddball Spring Sources
I forgot (not from the car book)
Century Spring Corp. LA CA 213-749-1466
They have a 350 page stock spring catalog that you might like -
compression springs up to 9.25" OD x 15.8" long 2004 pounds/inch.
The latter may be a bit much for your application.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
------------------------------
Date: Thu, 17 Jul 97 10:25:05 PST8
From: jcheeney@CCGATE.HAC.COM
Subject: LtWtRR Intake lengths
This may be rudimentary to you guys but here goes.
The intake runner length can be tuned based on the frequency of the
pulse and corresponding wavelength. The intake runner length is
matched to the frequency/engine speed you want. On a four stroke, the
pulse is delivered from the initial closing of the intake valve. I
agree that the pulse on a two stroke happens twice as fast relative to
engine speed and this will lead to shorter intake lengths. However,
I'm not sure how "deliberate" the pulse delivery mechanism is on a two
stroke and whether supercharging by shock wave position can be
achieved as easily and/or superimposed on exhaust tuning effects.
------------------------------
Date: Thu, 17 Jul 1997 17:02:41 -0800
From: "Michael Moore"
Subject: Re: LtWtRR Intake lengths
> I'm not sure how "deliberate" the pulse delivery mechanism is on a two
> stroke and whether supercharging by shock wave position can be
> achieved as easily and/or superimposed on exhaust tuning effects.
I have the impression that, at least on rotary valve RR engines,
they generally strove to make the intake tract as short as possible,
going so far as to mill back the mouth of the carb, etc. Presumably
this is in search of resonance at a higher RPM.
But then I'm not much of a two-stroke guy, so those that are can
probably fill you in on this.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
------------------------------
Date: Fri, 18 Jul 1997 15:04:22 -0700 (PDT)
From: David Dold
Subject: LtWtRR RS125s for sale
I just got off the phone with Corey from Miyuki Performance ... he just
received his new shipment of bikes which includes 2 1995 RS125s and one 1996
Hes got spare wheels, FCC Dry Clutch Kits ... the whole works
Prices in Japan have begun to go down, so the bikes he has now are starting
at $5250
Call him at 408 779 9151 or email MiyukiOB@aol.com
Corey's got plenty of character and product references bouncing around here
if you feel the need to check his past performance
Dave
May the forces of evil become confused on the way to your house
------------------------------
End of LtWtRR-digest V1 #38
***************************
LtWtRR-digest Friday, July 25 1997 Volume 01 : Number 039
----------------------------------------------------------------------
Date: Sun, 20 Jul 1997 08:40:48 -0700
From: "Bruce C. Anderson"
Subject: LtWtRR 80cc twin
Does anyone know of any 80cc two stroke twins? I may build an 80cc
roadracer and I'm looking for possible power plants to use.
Thanks
Bruce
VF500f TY350 YSR50 CMRRA #56z
------------------------------
Date: Sun, 20 Jul 1997 09:54:14 -0800
From: "Michael Moore"
Subject: Re: LtWtRR 80cc twin
> Does anyone know of any 80cc two stroke twins? I may build an 80cc
> roadracer and I'm looking for possible power plants to use.
> Bruce
Hello Bruce,
You may have to look pretty far afield for this. In the 1960s
Yamaha made a 100cc two stroke twin they called the Twin Jet, and
they even sold a GYT kit for it.
Tohatsu sold a 50cc twin street bike as well as a 50cc twin road
racer, but they are soooo rare.
Off hand, I can't think of any other 100cc or smaller twins that were
sold, though there may have been some domestic market bikes that
never made it to the U.S..
If you find something be sure to let us know about it.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
------------------------------
Date: Sun, 20 Jul 1997 12:43:49 -0700
From: "Bruce C. Anderson"
Subject: Re: LtWtRR 80cc twin
Hello Michael
At 09:54 AM 20/7/97 -0800, you wrote:
> In the 1960s
>Yamaha made a 100cc two stroke twin they called the Twin Jet, and
>they even sold a GYT kit for it.
This motor is one of the ones that I considered, but I don't know of
any way to reduce it to 80cc. Otherwise it would be a contender. This is
before considering the availability/cost of parts.
Bruce
VF500f TY350 YSR50 CMRRA #56z
------------------------------
Date: Sun, 20 Jul 1997 17:50:12 -0400
From: Bill Heckel
Subject: Re: LtWtRR 80cc twin
Bruce C. Anderson wrote:
>
> Hello Michael
>
> At 09:54 AM 20/7/97 -0800, you wrote:
> > In the 1960s
> >Yamaha made a 100cc two stroke twin they called the Twin Jet, and
> >they even sold a GYT kit for it.
>
> This motor is one of the ones that I considered, but I don't know of
> any way to reduce it to 80cc. Otherwise it would be a contender. This is
> before considering the availability/cost of parts.
Well, I think you could decrease the stroke and use a longer con rod
but if it's piston port .....
Maybe sleeve the hell out of it ( cooling problems ... )
Good luck
Bill
------------------------------
Date: Sun, 20 Jul 1997 20:29:36 -0800
From: "Michael Moore"
Subject: LtWtRR re: 80cc twin
Hello Bruce,
Joe has a 100cc Twin Jet dirt drag bike that he built for his son.
He might be able to supply more info on this bike if you need it.
"Joe Allan"
My friend Craig says he thinks the stock bikes have cast iron
cylinders (the whole thing, not just the liner). I don't know if
the GYT kit stuff is different.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
------------------------------
Date: Fri, 25 Jul 1997 17:46:29 -0800
From: "Michael Moore"
Subject: LtWtRR 50cc road racers
Karl Smolenski has updated his USCRA site with an article on building
his Suzuki AS50 roadracer. The link is:
http://kyalami.chess.cornell.edu/uscra/50ccinfo.html
Be sure to check out the other stuff on the site.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
------------------------------
End of LtWtRR-digest V1 #39
***************************
LtWtRR-digest Tuesday, July 29 1997 Volume 01 : Number 040
----------------------------------------------------------------------
Date: Sun, 27 Jul 1997 21:16:08 -0800
From: "Michael Moore"
Subject: LtWtRR Get a friend started racing
I was talking with my friend Jim last night, and the subject of what
he could use to start vintage roadracing came up (again).
In the past I've advised him on what he'd have to do to build an
AHRMA F750 Guzzi, and now that he has a 250 Ducati (and looks like
he'll be getting a 450 R/T Ducati in part exchange on his now-crashed
CX100 Guzzi) we've talked about what is involved with building and
running some size of Ducati single as well.
Jim isn't poor, but he does have a moderately new kid and bought a
house about 6 months ago, so he's not exactly flush with disposable
income. A Ducati single can be great fun to race, but if you get
started fixing blown up engines etc it can get expensive, as well as
time consuming to find parts.
Jim's mentioned a time or three about how much he likes my Honda
CR216, but if I were to sell it the price would not be
"entry-level". As I have to others in the past, last night I
suggested to him (again) that he build an AHRMA 200GP CB175.
Readily available cheap core motorcycles, many of the race parts
come from your local Honda or Kawasaki dealer, and they are reliable
and fairly easy to work on. Plus, you can be somewhat competitive in
the 250GP class too, giving you an extra class to ride in.
After chatting a while about this Jim was hot to start phoning the
salvage yards to try and find a 175. This didn't seem like the way to
go to me - better, I suggested, he watch the weekly "Advertiser"
classified ad newspaper or maybe advertise for a non-running 175.
Upon further thought, I remembered that I've got a CB160 in storage
that was given to me - it had spent a number of years sitting in a
field in the Pacific NW, and, while fairly complete and stock, would
be a real chore to try and restore. Also, the person who gave it to
me never came followed through on finding the papers on it, so it
looks grim for putting it back on the street. But as a core for
building a racer it is a good start.
So I told Jim I'd give that 160 to him if he'd actually build a racer
out of it. This gets him started, and even more important gives him
something in the garage that he can start poking at and bonding with,
making it more likely that he'll actually embark on the project.
Making a small space in my storage doesn't hurt either, and I also get
to sell another copy of my 175 tuning manual to bring Jim up to speed
on what needs to be done. I'd hazard that he'll be more than happy to
sell the rusty air boxes and stock body work stuff to someone for
shipping plus a mere pittance, which may also help someone elses
project along.
I know I'm not the only one with extremely dead project bikes sitting
in dead storage. If you've got something like my 160 that you've got
little or no money in, and know someone who's interested in building a
vintage road racer/MXer/trials bike, or just wants to get an old bike
and get it running to putt around on GIVE IT TO THEM. You know you're
probably not going to ever do anything with it, and it is more trouble
to chase the spiders out and take it apart to part it out at the swap
meet than it is worth.
Here's your chance to clear out some of the dead wood, help a poor
motorcycle get rolling again, and rope another unsuspecting person
into the vintage scene, all the while building up a store of good
karma for the future. Talk about your win-win situations.
Think about it.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
------------------------------
Date: Sun, 27 Jul 1997 21:38:37 -0800
From: "Michael Moore"
Subject: LtWtRR Current stats
As of 9:23PM Sunday July 27, the subscriber stats to the lists are:
LW RR - 33
V RR - 97
V Dirt - 54
Suzuki GS Twin - 32
MC Chassis Design - 105
I've noticed that things have been kind of quiet on some of the
lists. You know what that means - more posts from me. You have been
warned.
What's the deal? Don't tell me everyone is out riding motorcycles or
something instead of sitting in front of their computer.
MILESTONES: I think the Chassis list is the first to break 100
subscribers. I had actually thought that the two vintage lists
would have had a wider audience appeal.
SPAM: We've been lucky in escaping most of the spam that seems to be
hitting the other lists. Just a reminder in advance - if you get a
spam that comes to you through the list - DO NOT SEND A 'REMOVE' OR
SIMILAR MESSAGE BACK TO THE LIST!!!!! Besides, all the 'remove'
message does is give the spammer your email address so they can send
directly to you. If you must send a "remove" or similar message,
please make sure that you send it to the spammer, and not back to
the list - you'll just have to read it again, and so will everyone
else. C'mon, we're not talking rocket since here.
THANKS: I'd also like to thank those of you who have been
contributing to the lists - I've enjoyed reading many of the posts,
and have learned something from a number of them as well. I'm
pretty satisfied with the way things are going on the lists, though
a few more messages from the lurkers wouldn't hurt. You must have
something to say about the list subjects, or you wouldn't have
subscribed.
BOUNCED MAIL: A couple people are getting close to being
unsubscribed due to bounced mail. Of course, they probably won't
get this message. Remember that I'll cut you some slack for 3 or 4
days, but if things keep bouncing after that I'll unsub you and
you'll have to resubscribe. If you've gone for a week or so and not
gotten any messages from a list check with me and I'll tell you if
you've been dropped from the list. If not, I'll invite you to make
a post to the list so everyone will have something to read.
PICTURES: I've gotten a few neat pictures recently - but the rest of
you should remember that if you have a photo that you think will fit
into my graphics page I'll be glad to consider it. You can send me a
graphics file or mail me a photo for scanning if you don't have a
scanner. Please don't send me a 1MG .tiff file - try to keep them
below 100K, and most stuff seems to do well at 40-80K. Also, try to
view the photo first, and make it big enough to show the details of
your cool bike. Better a bigger photo with a bit more compression
then a tiny photo packed with indecipherable detail.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
------------------------------
Date: Tue, 29 Jul 1997 18:33:18 -0800
From: "Michael Moore"
Subject: LtWtRR Teensy fairings
One of the people on the race list wrote in mentioning that he was
thinking of putting RS250 bodywork on his RS125, as the 125 bodywork
seemed too small. I wrote in and mentioned that if the fairing
doesn't provide full coverage for the rider (no bits hanging out) it
is too small. Another list member rebutted that and here is my reply.
Since there are one or two racers on this list I thought I'd cross
post the reply:
********************
> I don't think you can say that as a blanket statement.
> the frontal area you have gained top end. From what I've read, what
> the last half of the bike looks like is more important than what the
> front looks like as far as Cd is concerned.
>
> I would think a fairing just smaller than the rider would be best.
Hello Todd,
You are correct that the back of the bike is most important, and soon
they may actually get some seats that are big enough to do some good.
The current big seats generally seem to be to pointed at the back, as
the sides of the fairing aft of the point of maximum width should not
have an included angle of more than about 10 degrees if there is to be
any hope of keeping the air attached to the bodywork.
As for the bits hanging out in the wind, all the fairings that I
know of that have been really developed in a wind tunnel (HD XR750
long track, Cosworth JPN Norton, Can Am Bonneville record breakers) as
opposed to being developed on some stylist's drawing board have all
made sure that the rider and any small bits are tucked behind the
fairing.
The boundary layer is very easily disturbed in the area of the
fairing aft of the maximum width, and those bits hanging outside of
the fairing are just the type of thing that the boundary layer finds
disturbing. Some of the 50/80cc racers went so far as to replace the
sewn-on lettering on the backs of their leathers with silk-screened
lettering as that resulted in better attachment of the boundary layer.
Don't get caught up in the race to minimize frontal area as you can
easily end up with a worse drag coefficient than a slightly larger
area with a more streamlined shape. This doesn't mean that you have
to have a Vetter Windjammer on the bike, as having the fairing where
there is nothing to fair in just adds unneeded area.
Pages 177-230 of your copy of John Bradley's "The Racing Motorcycle: a
technical guide for constructors" covers all of this in great detail.
One of the nicest parts in this section is a full page chart
documenting 39 wind tunnel runs during the development of the Can Am
Bonneville recordbreakers, coupled with another page showing various
configurations and a chart with the calculated power requirements for
a given speed for the different streamlining setups.
Cheers,
Michael
Michael Moore
Euro Spares, SF CA
Distributor of Lucas RITA and Powerbase products
Sole North American source of "The Racing Motorcycle: a technical guide for constructors"
http://www.eurospares.com
AFM/AHRMA #364
------------------------------
End of LtWtRR-digest V1 #40
***************************
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