welding crank arms

[meatwad]

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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!

I would measure the spindle length and offset and see if you can find a wider spindle. cheepo spindles are less then ten bucks and would be safer. (providing you have a crank puller)

 

[arkives1]

welding cranks

I would measure the spindle length and offset and see if you can find a wider spindle. cheepo spindles are less then ten bucks and would be safer. (providing you have a crank puller)

Thanks Meatwad, sadly I've checked out all the wider cranks I can find including the ones that are bent outward. So far no luck because the engine will have a pullstarter on the left side, that adds about 1.25 inches to the original engine width. I need to go about 1.50 inches wider. I doubt I can put that much bend in a crank with out really shortening the pedals arc or breaking the crank arm. James has shown me a good idea on how to use a spare crank part to widen the span.

 

[arkives1]

When I retrieve my camera thursday I'll take a closeup. Just a straight forward turning project(no carving). If looks if it looks like not to much of a project I'll send you one to copy. Of course this only if you allow me to recipocate.

Jim

I look forward to the picture. I won't need a piece to copy unless she's trying to match others? In which case I'd just replace all of them. Once set up making more than six is no problem. These are hand turned so not likely to exactly match the original which is why I suggested replacing all of the knobs at once. Probably most people wouldn't notice any difference but being a perfectionist to some extent, I'd notice any deviation at all. I often look at furniture I've built and I see every flaw, er, ah, "engineering change" I made in it.
I'll need to know what species of wood she's working with so I can match it. Most of those knobs were made of maple, pine or oak.

 

[AussieSteve]

Well, you guys have it figured, james65 and archives1.
This is OT, but what we need is a new section of MBc where we can swap skills etc.
ie. I'll make a circuit if someone makes a tensioner etc. etc.
... Steve

 

[arkives1]

Well, you guys have it figured, james65 and archives1.
This is OT, but what we need is a new section of MBc where we can swap skills etc.
ie. I'll make a circuit if someone makes a tensioner etc. etc.
... Steve

Steve, I do happen to have a design for a rigid tensioner for OCC Choppers and I have a picture of a spring loaded one I saw for sale somewhere, I forget where.

 

[AussieSteve]

Steve, I do happen to have a design for a rigid tensioner for OCC Choppers and I have a picture of a spring loaded one I saw for sale somewhere, I forget where.

Hello arkives1.
The circuit/tensioner thing was just an example. (Tensioners on the brain.)
Still, if anyone needs a simple circuit designed...
I'm in the middle of making a decent, foolproof tensioner for myself. I was also planning to incorporate a spring tensioner.
I had a nice long ride to the local garbage dump's recycling section today looking for metal, but tomorrow I'll go to a sheet-metal place and get exactly what I want - a piece of 3/16" aluminium about 2" wide to attach between two points on the frame, rather than the original one-point mounting.
My concern is that due to the offset of the roller on a standard tensioner, the chain has a tendency to pull the tensioner toward the spokes. There isn't much clearance. If the tensioner bracket bolts work slightly loose over time or the clutch is dumped at too high a speed with too much traction... bang.
The original rollers don't seem too bad, so I'll still use one of those.
Actually, an old roller cut down makes a good chain guide if the chain has a tendency to touch the tyre, (tire), or frame.

... Steve

This is what I'll make, except that I'll also have a slot for adjustment and use heavier gauge aluminium. Ideally, I'd like to get it TIG welded to the frame, too, instead of clamps. We'll see.
I love the stand, too. Does anyone know where they can be got?
(I can't remember who built this for credit):-

 

[Al.Fisherman]

Steve..I don't rember if I saw this on this forum or not. I may of got the idea in some post I saw, but this is how I did one on my friends bike. I'm going to change mine to this type (similiar) just that I'm going to use a spring loaded roller someone suggested from tractor Supply. Your design has a cleaner look.

 

[Al.Fisherman]

Well, you guys have it figured, james65 and archives1.
This is OT, but what we need is a new section of MBc where we can swap skills etc.
ie. I'll make a circuit if someone makes a tensioner etc. etc.
... Steve

Dang Steve.. That's a great idea. I cut ALL my studs (Class 8.8, Grade 5) ,the clutch cable guide, engine brace, boost bottle (old picture of a trial..not painted yet), and front engine mounts, but kind of hard to do without the bike, but can be done. Along with other mods I see incorporated on some bikes.

 

[AussieSteve]

Steve..I don't rember if I saw this on this forum or not. I may of got the idea in some post I saw, but this is how I did one on my friends bike. I'm going to change mine to this type (similiar) just that I'm going to use a spring loaded roller someone suggested from tractor Supply. Your design has a cleaner look.

Hello Al, another late night for me.
It's not my design, I can't take credit, but it is a good idea.
I've seen the spring tensioner from Tractor Supply. It looks good. Trouble is, they have no distributors here, as far as I know and postage from the states is murder. I've bought a sprocket, a 3L tank and a sprung gel seat lately and each time delivery was about $US40-45, ($AU45-50). My seat was $US26.95, but postage was $US45.90.
I would prefer sprockets to rollers, too, but the rollers seem OK so far.
I need the main (fixed) tensioner, then a small guide on the top chain run to stop it swinging side-to-side too much or it touches the frame lightly.
Also, due to rear sprocket runout, I need a spring tensioner on the bottom.
If I adjust the chain with the wheel turned to where the chain is tightest, it gets pretty loose when the wheel turns 180 degrees. The spring tensioner will alleviate that.
(For anyone interested, I have quite a collection of tensioner pics, must be about a dozen or so types, collected from this site.)

... Steve

 

[arkives1]

chain tensioners

Steve and Al, I like the idea of a two point support mounting. If you can get the chain just the right length maybe you won't need a slot. I do like the idea of a spring pulled roller though. I agree that the offset design doe's tend to pull the thing into the spokes. I've had that happen and had to replace a whole wheel on my cruiser. It also brought me to a sudden stop and I laid the bike down luckily not damaging anything else (including me)
If memory serves me right, the one I showed was meant to pull up on the top chain to prevent chain jump when slowing down and the chain is being pushed into the engine rather than pulled through by the engine itself. I'd think if the lower chain tension was right, it would keep the top chain straight too. I'd need to look at the chain as I slowed down to see what it's doing, personally, I prefer to see where I'm aiming the bike. Ive found that if I can get the chains on both sides just right, I don't need a tensioner with rear drop outs. I can adjust the tension on both sides with wheel movement. Unfortunately though, of my three bikes, only the chopper has rear drop outs and that bike presents a whole new challenge in tensioners.I hopefully have solved that problem with my occ choppers tension set up as it cannot twist since the frame is square shaped tube.
The designs you guys have would also make it very easy to attach a chain guard and keep it out of the chain, top and bottom. I'd prefer top and bottom guards on the chain. Imagine your pants leg being pulled into the chain at 30mph. Among all the clever, creative people we have on this forum, we're bound to find solutions.