broken frame

Because of the thinner tubing in bicycles is why I try to discourage motorizing road bicycles. Road bike tubing is even thinner. With steel frames they are much easier to weld on. Weight reduction cut outs can be filled in and flat bar or other steel tubing welded in to reinforce stress points.

Although my bike uses an alloy frame, and has travelled over 55,000 kilometers (34,000 miles) without any visible cracks, the benefits of a steel frame are more than durability; in that a heavy wall steel frame transmits significantly less engine vibration to the rider; making for a more pleasant riding experience.

I said "not dissimilar" not "same" I have laid eyes on a frame with tubing in it of similar diameter to bicycle tubing. I wasn't gunna go cutting on it to determine tube thickness on a whim.

074KU said:

I said "not dissimilar" not "same" I have laid eyes on a frame with tubing in it of similar diameter to bicycle tubing. I wasn't gunna go cutting on it to determine tube thickness on a whim.

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Then explain why a twin cylinder Matchless frame weighs 40 pounds while a BICYCLE frame weighs less then 10 pounds after all according to you they are not dissimilar materials. Kind of like saying a Chevette is similar to a Corvette I mean after all both have 4 wheels and a motor right?

I'm with you on that. Moped frames are thinner than motorcycle frames and bicycle frames are thinner than moped frames. The only way to make a bicycle stronger is to weld in supports and fill in weight reduction cut outs.

IbedaYank said:

Then explain why a twin cylinder Matchless frame weighs 40 pounds while a BICYCLE frame weighs less then 10 pounds after all according to you they are not dissimilar materials. Kind of like saying a Chevette is similar to a Corvette I mean after all both have 4 wheels and a motor right?

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I only said I saw the frame, and that from that I saw the tubes were of similar OD. 1.2mm tube may be all you can find for a modern frame. My steel frame bike which isn't much younger than yourself has tube thickness of around 2mm and weighs a hell of a lot more than 4.5kg (10lb) frame is closer to 10kg or (22lb) half as much weight yes, but I only have half the cylinders, I dare say less than half the ponies and half the weight of engine. I would even go so far as to say that my frame would not have cracked where and when it did had I suspension forks to absorb the shock stress of bouncing around in pot holes.

074KU said:

I only said I saw the frame, and that from that I saw the tubes were of similar OD. 1.2mm tube may be all you can find for a modern frame. My steel frame bike which isn't much younger than yourself has tube thickness of around 2mm and weighs a hell of a lot more than 4.5kg (10lb) frame is closer to 10kg or (22lb) half as much weight yes, but I only have half the cylinders, I dare say less than half the ponies and half the weight of engine. I would even go so far as to say that my frame would not have cracked where and when it did had I suspension forks to absorb the shock stress of bouncing around in pot holes.

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dont worry, doofus argues for the sake of arguing.

note, when comparing chalk to cheese, he tries comparing a bicycle with a harley. if that isnt chalk and cheese, i dont know what is. maybe it was the only frame wall thickness he could google?

try cutting into a yamaha scorpio frame... or any similar SMALL capacity motorcycle. crf50 springs to mind. something with an engine over 1000cc just wouldnt enter my set of equations. id still happily go to it with an angle grinder but

something thats actually comparable.

i would really love to chop into a cbr 125 fresh out of the showroom. im not going to check and see what type of frame it is, ill let doofus reign in glory as he returns and says its carbon fibre monocoque or something...

measuring a pile of old steel swingarms... rd250, 1.7mm, gsx 550, 1.6mm, fzr900, 1.85mm.

measuring a huffy frame, rear stays. 1.8mm.

its all irrelevant. engineering standards say tubing, weight for weight, is stronger than bar. its not the wall thickness alone. and good old gal water pipe, welded seam, may be 5mm thick, but its useless as framing material. ill trust my paper thin cromo over your thick wall mild steel anyday. round is stronger than square.

engineering standards mention the importance of correct manufacturing processes.

motorcycle companies spend lots of money to use the least frame possible while retaining strength. less material. more savings. more profit. they also like to get away with the lowest grade metals available. they order hundreds of tons, manufactured to their spec. not just a length or two off the shelf. every cent counts.

cheap chinese bike companies drop some pipe in a jig, show someone how to pull a trigger on a mig, and go for it... no xray, no heat treat, no QC on steel or welds or anything.

seems to work on the pitbikes at least

butterbean said:

I'm gonna have to disagree with the portion of the argument about the rider being overweight. A weak frame is a weak frame, regardless of weight. Perhaps a heavier rider will cause a weak frame to break more quickly, but the problem is still the weak frame. I weigh around 275 (here come the fat jokes, no I don't care if you don't like my weight and calling me fat won't answer the OP's question so move on already) and I have NEVER broken a frame, motorized or otherwise. My first two motorized bikes were built on department store bikes and the first one did crack, but I wasn't riding it and the motor mounts had come loose and the motor was vibrating violently in the frame. I believe that's what broke that frame. I had given it to a friend who did not maintain it as well as I did. My second frame still sits in my basement till I figure out what to do with it or get rid of it. The frame I'm riding now is a repop schwinn cruiser with quarter inch thick walled tubing. The bottom line is that a strong frame will carry a heavy rider without issue, and who cares if someone is overweight? It's perfectly logical to assume that an overweight person might get offended by the word fat, and it's an ugly, hateful word. No, I won't lose weight for you. I should not have to change for other people to accept me. I should not have to lose weight so people won't call me fat. It's my body and my choice. I'm not trying to pick a fight, but if you have the right to judge me, then why don't I have the right to defend myself? Fat is another word that hateful people invented, and using it to describe another person makes you hateful too. It's no different than being racist. Fat, h.o.m.o, the "N" word, white trash, hick, redneck, they are all the same.

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It sounds like you're more offended about it than legitimately disagreeing with it