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45 Frame Dimensions

Post Fri Sep 04, 2020 10:30 am

Posts: 12
Location: Bergen, Norway
Frame info needed! I'm building a race bike from scratch and have basically a front half of a frame , the rear axle plates and needed a bit of info. None of my books nor extensive internet searches came up with a frame blueprint, but it's surely out there. I found this Servi-car frame pic...I assume the front cradle from seatpost and forward is the same as a standard solo frame? From my books the wheelbase is 57.50". From this pic there is a dimension of 37.50" from engine CL to ??? Don't think its the rear axle centerline as it looks a bit long, or at least for a Solo...and are Std W models any different (rake for example) than their racing brethren WRs?

Thanks for any help!
Hans
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Hans

Texan-Norwegian Gearhead
Bonneville 200MPH Club Member
Instagram @hansrodncycle

Post Sun Sep 06, 2020 8:06 am

Posts: 12
Location: Bergen, Norway
So from reading all over the place there's not a lot of info on neck rake for the W or WRs. I took the Servi-car blueprint and cleaned it up a bit and added a simple Solo rear to it with some 18" tires. I then took a handfull of side pics and scaled them in Solidworks to a known wheelbase of 57.5" to get an average of dimensions. Of course using photos is not an exact science and rear wheel placement in the frame plays a role(so not exactly 57.5), but this give us a very close idea of Solo rake angles. The 23 degree listed in the Servicar blueprint makes sense as you need a much steeper rake for a serivcar or sidecar bike or you will have Arnold arms in no time. There is another "45 Frame" thread on here that mentions the 23 deg figure being from neck to motor plate angle, this is incorrect. 3 wheeled bikes, like tricycles, lessen the rake angle to get a much shorter trail making it easier to steer. The solo frame was desgined back when even the Big twins had fairly steep rakes and as bikes got heavier and faster the trail needed to increase to give high speed stability. A steep rake and short trail works great on a 45 as they are , for the most part, a light, low speed machine and it gives better control at low speed. It also works well on the WRs on the short ovals in the dirt , giving more feel to the rider with less effort. Tires and fork set-up play a major role in actual reake/trail. Lower the front and it decreases the rake and trail, making it turn in quicker...more twitchy if you will.
This at least gives me a good idea where to start on my frame build. Mine won't be 100% original anyway, hence why I would spend time piecing one together , instead of just buying a decent frame. As well I have a NOS neck and rear axle castings to repair the damaged castings, so might as well use them. And yes, I'm experienced in welding and brazing these old frames, having done this many times. Feel free to use these pics as you please. Any input/criticism is much appreciated.
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Hans

Texan-Norwegian Gearhead
Bonneville 200MPH Club Member
Instagram @hansrodncycle

Post Sun Sep 06, 2020 8:22 am

Posts: 12
Location: Bergen, Norway
Notice the Yellow and green WR form EJ Coles collection runs a smaller tire up front, which gives it a steeper rake than the two bikes above.
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Hans

Texan-Norwegian Gearhead
Bonneville 200MPH Club Member
Instagram @hansrodncycle

Post Sun Sep 06, 2020 3:17 pm

Posts: 41
Location: Victoria, Australia
Hans,
Good luck with the build. There are a lot of stories about WR's but some very knowledgable people still in America who know about such things. I am the custodian of the Red WR shown and can confirm it is a Std. WL frame, if a little beat up from its racing days. I can confirm it is running 19 inch wheels which may help with your calculations. I have had built a chrome Moly frame built locally, using WL dimensions for racing which has proven to be a little fragile. I have recently purchased a WR copy made with mild steel and have done one season with no problems.

Post Mon Sep 07, 2020 1:05 am

Posts: 12
Location: Bergen, Norway
Thanks Ozwalla! You have a beautiful bike, I hope it's OK that I used a picture of your bike, if there is any issue whatsoever I can take it down. Yeah, I've seen quite a few guys running 19s to get some extra ground clearance. Do you guys run the same rules as the Class C guys in the states? Just curious. I didn't mention in the first post what type racing I was building, but first off is to run it at Bonneville on the salt and then retire it to a street bike and part time racer on the ovals. For Bonneville to run int he vintage Modified class, I have to have the original font frame geometry, other than I can change the rake/neck, but from seat tube and back it can be modified with max of 10% extra wheelbase.

I have read about the orginal Chromoly frames being brittle. The thin wall and nature of chromoly combined with very rigid castings is not the best recipe. If i may ask, was your new frame you made fully brazed or tig welded as well? I assume they are cracking where the tubes go into the castings. One of the best attributes of brazing is that it's less rigid, letting the joint flex a bit, letting the tube move a bit more than a tig weld. I have few old road race bikes form the 70s/80s with handmade chomo brazed tubes(Dresda w 500 Honda 4, Moto Martin KZ 1000, Harris 900GPz), and they have zero cracking after decades of abuse. The bigger the brazing fillet the better as it spreads out the load on the tube. One thing I have done in the past on frames and springers as well that are in a high stress area is to put an inner sleeve in the tube in question. A key point is to taper the ID of the inner sleeve. It has full thickness at the point where it meets the casting, but tapers to zero at least an inch away. This spreads the high load at the casting end gradually, futher away form the casting. One of the biggest mistakes guys make when repairing frames and putting in new tubes is putting in a solid slug for alingment. This just causes a high stress area right at the slug as it is too rigid and strong compared to the tube on the outside. Any slug inside a tube should be as thin as possible or it should taper to zero. My process is to cut the inner sleeve and machine a taper on the inside and then press it inside your frame tube and put a quick weld on the end to keep it in place. This allows the inner tube to move inside the frame tube , adding bending strength, but not induce stress. You probably know all this stuff, just figured it might help someone down the line, even if repairing an old tractor...;) I made a quick sketch to help visualize what I was talking about if not clear.
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Hans

Texan-Norwegian Gearhead
Bonneville 200MPH Club Member
Instagram @hansrodncycle

Post Wed Sep 09, 2020 2:57 pm

Posts: 41
Location: Victoria, Australia
wr frame.jpg
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Post Wed Sep 09, 2020 11:40 pm

Posts: 1471
Location: Ojo Caliente,NM,USA
Quite often chrome molly breaking close to a weld is the result of welding with MIG or Tig and not normalizing. Any time you weld chrome molly with quick heat processes the whole part must be heated to dull red and allowed to air cool. Then if temper is required the whole part can be tempered.
Dusty


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