mounting motor to frame?

[retromike3]

don't drill or you will be sorry.

I had a seat tube brake on me because I drilled it. It was cut though like it was done with a hacksaw. I think the vibration of the engine along with the thin tube wall is a disaster waiting to happen. I tried to weld the frame back together with brass and T.I.G. with no success. It kept on braking.
I finally had to replace the frame and toss my old one out.

My advice is to keep away from the notion of drilling your frame unless you can reinforce the hole with a welded washer or plate to keep the hole from ripping.

Mike Frye the bike guy.

 

[AussieSteve]

Now you guys have me concerned. I considered getting the tube sleeved. Might go ahead and do it.
Meantime, I'll keep a good lookout for cracks developing. About 370km and no trouble at this point.
In my opinion, if this is such a serious problem, the vendors shouldn't be supplying the drill-type mounts with their kits. (That's what prompted me to drill.)
I've had almost enough of the BS involved with these things.
I've now heard 2 bad stories, I'd be interested to know how many guys have drilled and got away with it without problems, over a large number of km/miles?

Ron and Mike, how long after drilling did the tubes break?
Also, did the crack develop over time, or happen all at once, in one ride?
And, steel or alloy?

... Steve

 

[Al.Fisherman]

Steve..the bike that I drilled and cracked the frame probably didn't have 3 tanks of fuel run through it. I drilled the tube to hide some wires, I drilled out a nut that the water bottle rack screws into. Maybe a little to big, I don't know, so no more chances. If for ANY reason...if I ever see one...that I'll need to drill a hole again, I'll sleeve it, braze and drill. I saved the frame ...I repaired it. Also to be truthful...the frame was a thin walled mountain bike, and not that of my Cranbrook Cruiser. That might had something to do with it..I just don't know??? I do have pictures of the repair.

 

[stealthc9]

Not sure about the wisdom of that method, either. It places a lot of stress on the exhaust studs. It depends a lot on your frame, I reckon. I'll stick to drilling.

... Steve

A pic:-

I didnt put any stress on the exhaust studs, as I let the motor sit there and then clamped it where it naturally rested.

But I also used the highest grade bolts I could find on top of it. It lasted for over 1000 miles. on to my next bike, and then that bike was stolen.

 

[AussieSteve]

I drilled out a nut that the water bottle rack screws into....................... Also to be truthful...the frame was a thin walled mountain bike, .......

Same here. I'll keep an eye on mine for now and will probably sleeve the down-tube when the motor is out next.

... Steve

 

[Al.Fisherman]

Same here. I'll keep an eye on mine for now and will probably sleeve the down-tube when the motor is out next.

... Steve

Steve...my son was doing 95% of the riding (135#), neither of us noticed anything before it gave out, so I don't know it it happened all of a sudden or not. Thank goodness when it did he was in a parking lot starting it. He said ..it's a ride you don't want.

 

[CaptJ]

IMO: I think drilling your frame will make it weak. I needed to increase the height of the engine to clear the chain guard so I made custom mount, works well. Home Depot oak table leg 2.0" X 2.0" X 8.0" for $2.00. On the top of block it has a inlayed 1/8" X 1.5" X 3.0" steel plate with 3 holes in it and came with with my kit. I have 60 miles on it and I think it'll last over 60000.

have fun ya'll
Hi, ... Steve ... Ron
Steve I like your muffler mount I need to do mine.
... Jim

 

[AussieSteve]

IMO: I think drilling your frame will make it weak. I needed to increase the height of the engine to clear the chain guard so I made custom mount, works well. Home Depot oak table leg 2.0" X 2.0" X 8.0" for $2.00. On the top of block it has a inlayed 1/8" X 1.5" X 3.0" steel plate with 3 holes in it and came with with my kit. I have 60 miles on it and I think it'll last over 60000.
have fun ya'll
Hi, ... Steve ... Ron
Steve I like your muffler mount I need to do mine.
... Jim

The wood block is a good idea, Jim. It should absorb a bit of vibration, too.
That steel plate is the one I used, with an 8mm hi-tensile bolt in the middle hole, going through the frame.
Wish I hadn't drilled now. I must confess that I know engines better than I do bicycles and their potential weaknesses. Mine's an alloy frame, so I need to find someone with a TIG welder to sleeve the tube for me, within pedalling distance. There are a few metal-fab shops about.
It could be that mine will never crack, since it is a very thick tube, >2", (the muffler is thinner), and I have hammered it for almost 400km, (240 miles), with no cracking yet. I even pop monos, jump off kerbs and ride on rough dirt roads.
Still, after all the time and effort I've put into the rest, I don't want to leave such a potentially dangerous flaw.
Ron, I wish I'd talked to you about this before[/] I drilled that hole. I spent a few hundred dollars on this bike, brand new for the kit and hope I don't have to throw it or replace the frame. Since you mentioned brazing, I guess your's is/was a steel frame. Easier to work with.

On the exhaust bracket subject, it's a good idea. The mufflers are a bit heavy to hang off the 2 x 6mm studs, especially if they take a bang from something.

... Steve

 

[retromike3]

drill update

Mine failed about on hundred and fifty miles after I installed it and it happened suddenly. One day everything looked OK and the next thing I know my seat tube is rattling like crazy. I pull over and presto seat tube is sawed in half.
I can't say when it started to fail because I wasn't watching it propagate. I have fixed bicycle tubes on silver brazed bicycle frames before and it usually requires me to cut the tube in half(already achieved here) grabbing one half with a wrench and heating the weld up until it let go. Then if I am lucky I don't need to reshape a new lug or lugs, then I find a tube to replace it with and then copy the length and miter the angles to work with the frame.
After all that I place the frame in my jig to make sure its strait and level and then sliver braze it back in place. Then I repaint the frame and charge the customer a arm and a leg, because this job is a lot of work! With my frame I did not have that option because it was T.I.G. frame.
So if you have an option to put an engine on a bike frame by drilling though the main tubes my advice is DON'T.

Mike the bike guy

 

[AussieSteve]

Thanks Mike, we're getting the picture.
It's a shame there's such a small window for editing posts before they're locked up. I'd like to delete a couple of mine from earlier in this thread, to avoid misguiding people. Still, what's done is done. I hope I don't point anyone in the wrong direction.

On steel frames, if drilling is essential, a washer brazed to the frame before drilling the hole might stabilize it, I would think. Harder with alloy.

... Steve