Anyone cut off their top tube?
- Thread starter rocksalt27
- Start date
A fellow member is doing a midframe pocket bike engine build on a BMX.
It's a very tight fit.
However, all the tubes and stays will remain unmolested.
So far, the only welding to the bike will be a triangulated brace from the bottom tube to the motor mount.
It's a very tight fit.
However, all the tubes and stays will remain unmolested.
So far, the only welding to the bike will be a triangulated brace from the bottom tube to the motor mount.
Wouldn't the engine itself act as a brace to keep the frame from collapsing?
It depends where and how the engine is mounted.
Yes, I've seen instances in old board track racers, where the engine block braced two sections of the frame's down tube.
However, the bike's top tube was intact.
FWIW, I ran an electric hub, rear friction drive, and front and rear friction drives on a girlie cruiser.
It had no top tube, but the bottom tube was heavily braced.
When loaded to 6 SLA lead batteries, I could literally FEEL! the bike's frame twisting, ever so slightly.
Yes, I've seen instances in old board track racers, where the engine block braced two sections of the frame's down tube.
However, the bike's top tube was intact.
FWIW, I ran an electric hub, rear friction drive, and front and rear friction drives on a girlie cruiser.
It had no top tube, but the bottom tube was heavily braced.
When loaded to 6 SLA lead batteries, I could literally FEEL! the bike's frame twisting, ever so slightly.
Related but different. I found a girls beach cruiser and cut the top tube and rewelded higher. People love the frame and it’s had no issues over 7 years. My old welds were pretty ugly but strong . The fenders didn’t last. I welded in a tube in the back for rear engine mount
That's KOOL and like how the engine sets more level.............Curt
My opinion, that's a "Dead Man's" choice.
Unsafe at any speed.
Even a 20" bike would be squirrelly to handle above jogging speed.
(Ask me how I know that.)
I'd choose at least a 24" bike.
You better mount them training wheels like you'd mount wheelie bars bro cuz I have a feeling you're going to be flipping over backwards if you're not careful.
