welding crank arms

Discussion in 'Painting, Welding, Bending and Gas Tanks' started by arkives1, Dec 7, 2009.

  1. arkives1

    arkives1 Member

    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!
     

  2. Mountainman

    Mountainman Active Member

    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
     
  3. motorpsycho

    motorpsycho Active Member

    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: Dec 7, 2009
  4. arkives1

    arkives1 Member

    welding cranks

    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!
     
  5. Al.Fisherman

    Al.Fisherman Active Member

    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.
     
  6. arkives1

    arkives1 Member

    longer or wider crank

    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.
     
  7. motorpsycho

    motorpsycho Active Member

    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.
     
  8. AussieSteve

    AussieSteve Active Member

    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
     
  9. arkives1

    arkives1 Member

    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"
     
  10. Al.Fisherman

    Al.Fisherman Active Member

    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.
     
  11. james65

    james65 Member

    Extending crank arm

    On my first build, I had to move the crank arm out to clear the pull start. I cut the end off a steel crank arm. Also cut the end off a tapered crank arm shaft. Welded them together, drill through them and used a longer bolt. Worked great(pictures below). On later bikes I just bent an offset in a steel crank arm, also worked great.
     

    Attached Files:

  12. james65

    james65 Member

    Archives1,
    You told me(PM) that you have a spare crank arm. Cut off the end where it mates to the taperd shaft. Butt it up to the inside of your other crank arm(keeping the tapers aligned and weld them together. Use a longer 6mm bolt to reattach.

    However bending an offset in the arm using a vise and large wrench is even easier.
    You really don't feel any differance when pedaling.

    The red bike has the offset pedal(also apple fuel tank).

    The black one has the welded crank arm extension.
     

    Attached Files:

  13. arkives1

    arkives1 Member

    James great advice, I'll try bending the spare arm first, if that fails to give me enough clearance I'll cut and weld as you suggest. I notice that you have some sort of jackshaft and shifter on the red bike. Details please! You know how we are on here, we want to know everything. I don't see a candy apple gas tank though. Both bikes look great, I still don't know how you ride far with that seat though. I like the look but man, did my butt hurt. What sprocket are you using on the black bike and do you have enough hill climbing ability with it?
    I have to either find a right angle fuel shut off or a different gas tank. The outlet on my tank goes straight back to the small end of the tank and lays very close to the frame so I cannot get the fuel line connected with out a sharp bend in it and an inline fuel filter is out of the question.
    If I like this chopper when I finish it I may do another one to ride at my summer place, that's much more open and rural, lots of winding back roads around the many lakes in the area. For that one I'd like to do a jackshaft/shifter arrangement if I can fit a gear case in the rear wheel space. I'd also like to go to disc brakes on that one if I can do it. I have pics of Byrons build that look possible to do. Keep building!
     
  14. james65

    james65 Member

    The red bike has a apple juice can tank in the bag, behind the seat.

    The picture of the black bike may have the old 44t sprocket, have changed to 32t.
    Hill climbing iwith the black bike is so-so. I now know from experience that adding a tuned pipe will resolve that problem.

    However I built the red one for a test bed, five speed, tuned exhaust and integrated mtr mount/jackshaft.

    The black bike has a hidden tensioner(spring loaded)

    As for the seat! Yes it was a pain in the ***. I resolved that by making a seat that works great(nice and comfy). Used the seat all summer and I ride some bumpy semipaved roads. See attached pictures.
     

    Attached Files:

  15. james65

    james65 Member

    You can extend the tank outlet using a male to female adapter. however if you install the shutoff in the tank before mounting the tank, it should fit.(this is what I did). DO NOT run your bike without an in line filter(personal opinion).
    Be sure to use a good fuel proof gunk when installing your shutoff.

    Here is a pic showing shutoff, filter and DIY filter mounting bracket.

    Also included pic of steering limiter.
    Keeps handle bars from flopping around(bicycle style) and more like a Mtr-Cycle. This also lets you clean up the lengths of your cables.
     

    Attached Files:

  16. arkives1

    arkives1 Member

    Thanks again James, The seat "springs" are a flash of genius. Very clever. You certainly have the skills to do these bikes. I like the set up for the handle bar limiter. Mine has two little rubber padded screws to stop it but they are about useless. I'll intergrate your design into my plan. Making the jackshaft mount a part of the engine mount is a great idea also. Unfortunately, I have to have all my machining and welding done by others, not much equipment to work with metal here. I do mostly woodworking in my own shop. My local muffler shop has been great about welding things for me, I just buy him a case of beer now and then. I was a patternmaker during my working life but that too was mainly wood, there is a pattern shop near me that has been kind enough to do some minor machining for me. They can't allow me to use any equipment of course because of liability concerns. I take the whole crew there a couple of dozen doughnuts now and then as a token of appreciation.
    You're absolutely right about an external fuel filter, both my cruisers have them and I will get one on this bike somehow. The tank on your bike is different than mine, having more of a downward angle, mine goes straight back toward the seat along the frame line. I can get the shut off in ok, it's just poorly positioned for this particular bike. I will switch tanks with one of my cruisers as they both have different tanks that will work better. I used teflon tape on my shut off valves, no leaks so far but I do have gas proof putty as well.
    Before I mounted any of my tanks, I filled the tank with small stainless screws and nuts along with some very course sand. Then I strapped it to a paint shaker for awhile and it cleaned any rust out beautifully. I made sure I did a very good job of cleaning the sand out. I've had all my tanks chrome plated inside.
     
  17. james65

    james65 Member

    I purchased a jack shaft (2 bearings, 5/8" shaft w/keyway and two bearing mounts(flat washer style "didn't use them"). That cost about $38

    Bearings fit perfect in black iron pipe from home depot.
    Bought a freewheel hub adapter 15mm bore. Turned the end of shaft down to 15mm, easier than opening the bore.
     

    Attached Files:

  18. james65

    james65 Member

    Arkives1,
    Perhaps we could swap some skills. I have a milling mach(small, a metal lathe and small welder ect.)
    My sister asked me to make 6 duplicate wooden drawer pulls for her. I can do it on my harding but wood is not my expertise.
    Perhaps I could make something for your MB project in exchange for you making the pulls.


    Jim
     

    Attached Files:

  19. arkives1

    arkives1 Member

    Jim, I'd happily make the pulls for you just because you've been so helpful with my bike. You've certainly saved me from having to do all the engineering on some of these things. I don't have a lathe in my home shop but I do have access to one. My lady's brother lets me use his but I have to sharpen all his turning tools for him, he doesn't know how.
    I need a picture or a drawing of what she needs along with dimensions. I don't do any carving. I tried but my carving looks like I dropped a chainsaw on the piece.
    Larry
     

    Attached Files:

  20. james65

    james65 Member

    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
     
Loading...