welding crank arms

arkives1

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Oct 25, 2009
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Milwaukee, Wisconsin
I'm building a chopper and need to cut and fit a piece in the left crank arm to widen the space for the engine. Wider cranks available will not go far enough. Mine is a 3 piece crank and the arm appears to be a casting or a forging, I'd guess casting. I want to keep the crank arm the same length as the right side is now by cutting the arm and welding on a piece of high strength steel tube and weld the pedal holding piece back to the added steel. Has anyone done this? I do not weld nor know anything about welding so I need to know if these arms are weldable with out softening the arm too much. I know there are a good many welders in the forum and hopefully some one will enlighten me before I cut the crank. Thanks guys!
 
hi
for now don't do anything until
you show it to a professional welder
and then if it is cut and welded for you to proper distance
keep an eye on that THING for possible cracking as the miles add up

I thought that there was someone selling those extra wide cranks ??

have fun as you ride that THING
 
if your cranks are cast or forged aluminum (most are) you can not weld steel tubing to the aluminum. you will have to use a peice of aluminum as the spacer and it will have to be TIG welded together.
TIG welding can get expensive if you have a professional do it..but, the area that will need to be welded won't be that big, so it shouldn't be too expensive.
if your cranks are cast or forged steel, then welding a steel tube to them won't be a problem. this would have to be MIG welded.
 
Last edited:
welding cranks

if your cranks are cast or forged aluminum (most are) you can not weld steel tubing to the aluminum. you will have to use a peice of aluminum as the spacer and it will have to be TIG welded together.
TIG welding can get expensive if you have a professional do it..but, the area that will need to be welded won't be that big, so it shouldn't be too expensive.
if your cranks are cast or forged steel, then welding a steel tube to them won't be a problem. this would have to be MIG welded.

See! I knew I'd get good info from other members. Luckily I'm certain my crank arm are not aluminum, they are steel according to the magnet I tried. Likely Chinese steel as these bikes were made in China for Schwinn and no longer made. I got lucky and found one still in the box at a fair price. It's a winter project and I won't even get to try it out until spring. Here is the frozen tundra of Wisconsin, that may be next June.
I have no idea what TIG or MIG means but I'm sure other members will as you do. Thanks for the great info!
 
If you do lengthen the crank, be especially careful when making a turn. My son and I built a chopper for him, and the first time I rode it (was the LAST) ..good bye to knee skin. The peddle hit the pavement while I was making a left turn and the left peddle was extended. Peddle dug in and threw my azz.
 
longer or wider crank

If you do lengthen the crank, be especially careful when making a turn. My son and I built a chopper for him, and the first time I rode it (was the LAST) ..good bye to knee skin. The peddle hit the pavement while I was making a left turn and the left peddle was extended. Peddle dug in and threw my azz.

I hadn't thought of that possibility but it does make sense, I'll try to remember that and wear knee pads etc. I've laid a bike down a couple of times and lost skin to road rash. As my friend Mike says...thats why so many bikers wear leather and/or chaps.
 
yeah, my friends low rider schwinn sits so low to the ground that you can not peddle it. both peddles will hit the ground if you rotate them.
we made up a lock, to lock the cranks in a horizontal position so they can not be accidentally rotated. we made the lock with a little slack in it, just enough to rotate the cranks backwards to use the coaster brake.
the first time we rode this bike, the cranks would rotate 360 degrees, we did not have a chain on it, and no brakes. we used the peddles as brakes...we just rotated the cranks backwards and drug one of the peddles on the ground to stop. not very good brakes, but it did make one heck of a spark show when riding at night.
never crashed due to a peddle digging into the ground, but i can see how it can happen. especially if it is the forward facing peddle that hits the ground.
 
I did it a few weeks ago on my electric bike. Ouch. It has suspension and if it compresses too far while cornering... You should see the pedal.
... Steve
 
dragging a pedal when cornering

I have never snagged a pedal but I can vividly remember the brake arm band on an old schwinn breaking while I was flying down a steel hill. This was back in the 50's when I was growing up in the mountains of Virginia. It's funny now but at the time it was scary. I ran off the road on an outside curve and went down a steep embankment and was stopped by a wire fence. The bike stopped, I sailed over the fence into a muddy cow pasture where the resident bull chased me back across the fence faster than I flew in. I pushed the bike up to the road and walked it home. Mom was upset that I was so dirty and smelled so bad of cow manure. Dad of course thought it was hilarious. He teased me for years, when ever I came home later than expected he'd walk past me going "Sniff, Sniff, Whewwwweee"
 
I have never snagged a pedal but I can vividly remember the brake arm band on an old schwinn breaking while I was flying down a steel hill. This was back in the 50's when I was growing up in the mountains of Virginia. It's funny now but at the time it was scary. I ran off the road on an outside curve and went down a steep embankment and was stopped by a wire fence. The bike stopped, I sailed over the fence into a muddy cow pasture where the resident bull chased me back across the fence faster than I flew in. I pushed the bike up to the road and walked it home. Mom was upset that I was so dirty and smelled so bad of cow manure. Dad of course thought it was hilarious. He teased me for years, when ever I came home later than expected he'd walk past me going "Sniff, Sniff, Whewwwweee"
Keep in mind when we were growing up we didn't have choppers like they have today. All we had was anything we modified. Todays choppers's peddles are about 3 inches from the ground.
 
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