Crankshaft Material?

Jimbo

You can fool some of the people some of the time
What is the type of steel used in a typical 2 stroke crank?
Like a KT 100 or KPV crank?
The journal is very hard and can't be filed but the actual shaft and the counter balance / web is soft enough to be filed.
 
Crankpin material –20CrMo
(Chromium nickel Alloy steel) Is what I found on the internuts Jim. I have also done some searching for a good assembly jig and found they are quite pricey. Luckly a motocross builder I know is willing to let me use his that he made that is better than the OEM one that he has sold and is willing to help me make my own. The crank halfs of the rotax seem to be forged where as the ICC Italian motors I have seem to be just machined steel.
 
The material is pretty much proprietary information.
Ask ARC what they use. Be prepared for no answer.
There is no need whatever to attempt to build a crankshaft.
 
Crankpin material –20CrMo
(Chromium nickel Alloy steel) Is what I found on the internuts Jim. I have also done some searching for a good assembly jig and found they are quite pricey. Luckly a motocross builder I know is willing to let me use his that he made that is better than the OEM one that he has sold and is willing to help me make my own. The crank halfs of the rotax seem to be forged where as the ICC Italian motors I have seem to be just machined steel.

Can you take a picture of the jig and share? I gotta build one for myself. These big 250/450 cranks are pretty hefty . I found just cutting the rod and pin first to remove the old one saves me from potentially distorting the crank. But I'd love to see ideas on a fixture press.
 
Crank jig is easy to make but first you must realize you're not aligning the crank when you press it you're just getting it close. Take a 1/2" steel plate, bore a hole in it for the pto and mount 3 steel blocks on it and make one block moveable. Adjust the blocks for a sliding fit on the OD of the crank webs. Then you need a thick block to go over the top crank web to press it down. You use shims under the crank pin to get it on center. Easy to make if you have a mill.

Sundog
 
Most cranks rods are made of a 20 series chome nickle alloy like 8620 then carburized ( hardened ) in the areas requiring hardening while leaving the remaining areas soft.
The best cranks fixtures are the Italian type using 2 heavy wall tubes that are machined to glide one over the other with a plugged end for the crank to pass thru and a machined slot in the side for the rod to extend thru then all is required to do is press the assembly together ( you must fit the pin first ).
check out Vamec web site in Italy
Mike
 
The first video is just like the jig my friend built. Booth videos use the same concept where the pin and holes are clocked into position so that little if any after alignment is needed.
I like the four post jig better. I laughed at the idea of pressing the pin through that was in the second video. That does work IF the pin isn't damaged, but then most cranks that I have to press apart is because the pin is damaged, so I use a plate that fits between the webs that allows the bottom web with the pin in it to fall out from the top web.

PD Before you die I hope that you have the need to at least rebuild a crank shaft and that someone will help you with your attempt. LOL
 
Most cranks rods are made of a 20 series chome nickle alloy like 8620 then carburized ( hardened ) in the areas requiring hardening while leaving the remaining areas soft. Mike

I am sure Mike all ready knows, yet I thought I would add that the reason for the copper coating you see on the rod is to protect the none bearing surfaces from the carburization process.
 
Thanks Magmo
One more question.
Some of these cranks have the pin welded in place.
Is there a special welding process used for this?
What rod or wire is used?

Oh yea saw that video already and i agree with him about the washers etc etc
You should also know that they can't make bolts with the head in the center of the shaft.
http://www.fastermotors.net/BuyAmerican.html
 
Freezman. Again sorry about straying off topic. I cast cases in my garage. I use automotive castings to melt mostly of 356 alloy. I currently harden them by solution cooling by trying to get the casting in the water before it drops below 900 degrees. I then bake the casting at 350 degrees for 10 hours to temper. Any home based ideas on improving the hardening and tempering process? I'm thinking your the guy to ask tim
 
My dad has a jig for doing crankshafts. Seems like it was a 1/2" steel plate with fixtures on it to line up the crank halves before pressing them together. It gets it pretty darn close to perfect. It's pretty nice setup. I used it a few times.

Frankie
 
The first video is just like the jig my friend built. Booth videos use the same concept where the pin and holes are clocked into position so that little if any after alignment is needed.
I like the four post jig better. I laughed at the idea of pressing the pin through that was in the second video. That does work IF the pin isn't damaged, but then most cranks that I have to press apart is because the pin is damaged, so I use a plate that fits between the webs that allows the bottom web with the pin in it to fall out from the top web.

PD Before you die I hope that you have the need to at least rebuild a crank shaft and that someone will help you with your attempt. LOL

I never pushed the pin straight through. I think most use a plate and push pin back out the same way it went in. But then I also saw a guy on youtube putting a 2cycle cylinder liner in cold with a press. Nasty stuff.
 
Looks to me to be just a power press die set, where the actual punches and dies are mounted. I used 1" surface ground steel plate with Steel shafting for alignment pins.
 
Tim Taft, I hate to burst your bubble but I am not as schooled as you might think. I have enjoyed your home photos and am impressed with your operation. I have a few good books that I will have to review to see if a better recipe is available. I do have a 300 below cryogenic processor that would enhance the heat treatment yet it probably doesn't fix a part that hasn't been properly heat treated. I understand that a cycling of tempering may be better. 350 for an hour than cool to room temp 3 times. In fact that is what I do to parts after they have been cryogenically treated which is suppose to stabilize the newly formed matrix.
 
You said matrix so your more schooled than I lol. I attend the university of utube. My current system is based off old military videos education products in the field of metalurgy. I wouldn't be able to do half what I do with out it. The process I use makes a huge difference in machining the alloy. With out it its soft and you cannot get a nice clean cut. Its milky and soft. After hardening with out tempering its still not able to make nice clean cuts. But after a 10 hour heat soak. It cuts clean it gives that rainbow shine and it holds cuts and holds a thread a 1000 times better. The study ive done teaches the temp control variance in different temper ratings 10 hour heat soak is supposed to give a t6 temperament. I'd ask allot so I can learn allot. Thanks for the reply. Tim
 
PD Before you die I hope that you have the need to at least rebuild a crank shaft and that someone will help you with your attempt. LOL
No way that's happening! A man must know his limitations! 3 piece crankshafts hit my limiter.
Also, I've had a 20 relationship with the Falicon brothers. All things crankshaft.....Falicon get's the work.
 
Material has nothing to do with a files ability to cut it, heat treating does. Temperature controlled ovens, liquid salt baths, quench tanks, Durometers, etal. are how you get to what you need.
 
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