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Old 01-22-2009, 09:27 AM
Creative Engineering Creative Engineering is offline
Join Date: Sep 2008
Location: Clearwater, FL
Posts: 1,668
Default Re: New Build (raw engine)

Originally Posted by fm2200 View Post
Many years ago I read in a motorcycle magazine never drill a hole in any frame ever. Im just cautioning,you because no one can see metal fatigue.
This is a valid concern, especially in Aluminum. A large drilled hole in thin material such as frame tubing isn't round. There is not enough metal to fully engage the drill so it "corkscrews" into the metal and you end up with a hole that has 3 distinctive points...sorta like the rotor in a Mazda rotary engine. These points are where stress cracks can begin to form and spiderweb a good distance before the tube let's go in an instant. Ideally the hole should be reamed round after drilling and the edges radiused and polished. Time consuming...yes. Save you from a nasty spill from a broken frame; possibly.

Rigid mounting this particular engine is also a bad idea as the vibrations can induce stess cracks. Think of an opera singer who can resonate a wine glass to the point of shattering. I know this is a moot point because dampened mounts aren't available for the many frame styles. Just keep a close eye on your frame.

I've been reading posts for about 5 months and I have yet to hear about a catastophic failure...just beware it can happen and check your bike often.

It appears that interest in motorbiking is expanding weekly. With this there will be the potential for problems. Possibly major problems!


Not knowing any better, (not mechanically inclined), a guy goes out and buys the cheapest aluminum-framed bike he can find. With minimal tools he hacks and whacks in haste until the engine kit is installed. He then proceeds to ride it full blast everywhere he goes never checking the bike out for problems. Something let's go and he's seriously injured.

If it happens enough, a law will be passed that bicycles can not have engines...motors only, and we will all be forced to quit, or go electric.

In the interest of cost savings, department store bikes have become ever lighter and cheaper. The frame tubes are of a thinner cross section, the bearings are acceptable for low speed only...with 25MPH bursts such as when peddaling. Basically they are marginal for thier intended appication...add an engine and you must be careful. Add one more factor; many of us, myself included, are 200+lbs.

I ride my bikes fast, but they are engineered to do it safely. Nothing has been left unchecked.

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