Christmas quiz No 1

[David Lahey]

OK today there are two very different motorbike frames in a bare state sitting in my shed.

Both frames were made in 1975. One is a Yamaha TY175B (painted silver), the other a M138 (350cc) Bultaco Alpina (about to be painted silver)

Which frame is heavier?

[chippy]

David,
My guess would have to be the Bultaco frame is heavier.

Andrew

[mike-b]

Hi

Looking a both the Bultaco looks to have larger tubing but that's to easy so i will go with the ty frame

[Mark K]

The Bultaco has larger diameter tubing which at first glance makes it "look" heavier. The Yamaha seems to have more flat metal in the form of brackets and bracing, particularly in the area of the under tank toolbox, which probably more than compensates for the built-in bash plate on the Bultaco. I've heard that old Spanish bikes typically had lower grade softer steel in the frame, but that doesn't mean it was necessarily lighter. Actually on thinking about it, the larger diameter on the Bultaco probably means a similar strength could be obtained with a thinner tube. Its only a guess, but I'd say the TY was heavier, mainly because you wouldn't be asking if it was all that obvious.

[Greg Harding]

Hi Everyone,

David, TY250B is the lightest of all the Japanese 250 frames (lighter than the A model as the stand is in the swingarm!) So my thoughts are TY175B frame is lighter than the Alpina, suppose I have a 50% chance of getting this right.

[cota]

could be trick question / answer - if the silver colour paint was "cold gal" then likely to add a good deal of mass just to keep centre of gravity low and make sure that bike exceeds the new FIM limit for mass (kg) for the WTC!

[Bully fanatic]

Well I don`t know the answer to this one but I know which frame I would rather have with the rest of the bike in a shed. No it is not the TY. I can remember my M 213 frame was pretty heavy with the swingarm still on it. A 158 is reasonably light and so is my 199 B which I have just had in a thousand pieces. The Pursang frames are quite light too except the really old ones. They used chrome moly from 1974 on the Pursangs but I think the Alpina`s were mild steel. I know I could arc weld my 213 easily. Now I think on it I don`t think I have ever picked up a TY 175 frame before. Graham.

[Mark K]

Well I don`t know the answer to this one ..........

But Graham, you can't say all of that and then not have a guess. I've never picked up a Bultaco frame before, but little things like that don't stop me. You can't sit on the fence forever. Surely you must pick one side or the other to stand on, or can you keep your feet up forever?

[Jon V8]

I think its a trick question,but then as said its a 50% chance.... My thinking is that the Bully frame will be made out of low grade thick wall tube like my early Cota frames.Before I nailed the Serow XT225 motor into my Ty175 I cut out nearly all of that toolbox area, the bits are still on my welding bench,they dont weigh much.So I'll say the Bully frame is the heavy one.
Merry Christmas to all !

[JC1]

I'll say the Alpina frame is lighter. The 138 model was said to use cro-mo tubing. Well, spanish cro-mo tubing anyway & it wasn't too good quality. In reality it was probably just thin-walled mild steel. Every 138 frame I've seen bar one had cracks everywhere, like you've shown in the other thread David. I've had one that was so cracked & bent it was beyond repair. The tubing is very thin-wall & they are pretty light. (They soon went back to thicker mild steel tubing on the Alpinas.)

Having said that, I've never felt a Ty175 frame, but I'll run w the 138 frame being the lighter.

Oops. just noticed the quiz said which is heavier? TY