crank shaft too short

[scottydog]

Hi was wondering if any one could help with where i could get are keyed shaft extension in the uk. Was thinkng of welding it on about 100mm as i have to no access to a milling or lathe.

 

[r_chez_08]

dont weld onto the crankshaft! ant pics?

 

[devino246]

dont weld onto the crankshaft! ant pics?

Makes it impossible to remove the side cover.

 

[r_chez_08]

and can melt seals, deform shape, weaken, not run true etc.

 

[anderkart]

Scotty, can you post a pic of your engines output shaft?

 

[archer1232]

I had a honda gx 120 with a short crank shaft that was 3/4" stepped down to 5/8" which was threaded. It was to around an inch to short so i drilled and tapped the crank to 3/8" threads and took a peice of 3/4" roundstock with a 3/8" bore and bolted it to the end of the crank. Then i put the clutch on and then fully tightned the bolt (this makes sure the roundstock is perfectly alligned with the crank. then i took the clutch off and welded the roundstock to the crank. Make sure the crank doesnt get to hot. Lastly i made a key way with a dremel and fit the clutch on. The clutch fits perfectly and is pretty much perfectly true.

 

[scottydog]

shaft

Thanks for the quick replies.
done some small tacks at the tip to see about trying to line it up. Brutal to get straight and never thought of the seals being damaged by the heat. The threaded hole is 10mm and the shaft is 19mm.
Archer1232 your way looks sound enough.

 

[r_chez_08]

hmmm. interesting.
do you have a machine shop locally? if not i could make you an adapter for a small fee. need to think of how to hold it on though do you have a dremel?
rob

 

[scottydog]

hi rob dont think theres a machine shop but i do have a dremel
whats on your mind

 

[r_chez_08]

Make a small keyway with the dremel in the shaft. then i could make an adapter that goes like this =- with a keyway and grub screw in. then that will slide onto the shaft and get held on by the keyway and grub screw and it will give you a usable 3/4" at the end.
edit: green= adapter
blue= grubscrew
orange= keyway
black=shaft

 

[scottydog]

would be much appriciated though it would need to be about 18mm dia with 8mm threads if you could manage that ok

 

[r_chez_08]

18mm? what is that for? do you mean the usable bit? and do you mean 8mm thread in the end? what size keyway?
i wont be able to make it for another week, as the machines are at school, and im at home, on half term.

 

[Bluethunder3320]

how about put a sprocket on the engine shaft, and run it to a JS?

of course keep the gearing the same on the JS because of the clutch engagement RPM.

 

[scottydog]

i was was thinking of down the lines of the pic so it could screw in. Then put a few small taks just to hold it more securely. Its too attach a torque converter it is a bit narrow but should tuck away nicely

 

[r_chez_08]

i thought of putting a thread on the end, but it would unscrew?
18mm? they are usually 3/4" bore. and why 2mm deep?

 

[scottydog]

it's a small key from end to end. this is one disk to show the small diameter.
was going to do some tack welds so it wouldnt unscrew and doesnt produce so much heat to do any damage.

checked it more closely and your right it is 3/4"

 

[r_chez_08]

but you wouldnt be able to take the side cover off if needed. it would be better putting a keyway in or buying a new shaft.

 

[scottydog]

I know what mean though but if the welds are small but strong enough to take the stress and still be easy to cut with a small grinder. Im no too clued on engines that i would be opening the side or changing the shaft unless the engines dead.

 

[DCProductions]

I have an idea. Engine crankshafts make great lathes. I would weld all but the key-way, crank the engine up, and lay a file on the weld. The weld should penetrate deep enough so that, when you file the shaft flat again, the extension still holds strong. If there is any "un-true" portion of the extension, file or sand it off. Even if the extension is ugly, it will be better than having a short crankshaft.

If you file the weld you should have no problem getting the side cover off (unless I'm missing something). However, I do understand the concern about seals heating up. I would have a hose on low pressure pouring over the shaft right next to the crankcase.

Hope this is good advise. Also, correct me if I'm wrong! I may do this to my engine.

 

[r_chez_08]

good idea. if you want me to make the adapter i can make it in a few weeks, it will probably be about a tenner for the postage and materials etc.
if you tell me the exact sizes i will make it.
rob