Pinning a Crankshaft

[dicej32]

I'm making a built up crankshaft for my Upshur engine. What are the options for the pin? Do you use a dowel pin? Can a pin and loctite work as opposed to a pin and soft solder? Does the drilled hole for the pin have to be reamed under size? Any other options?

Thanks,

Jenaro

 

[AllThumbs]

I have used locktight, and tapered pins. I have also used locktight and then drilled through, tapped, and installed long set screws with red locktight.

E

 

[Mcgyver]

loctite has around the same tensile strength as soft solder, around 4-5000 psi irrc. In any event you're never going to come close to over torquing either joint in a model. I go with loctite just from an ease point of view. Different # have different gap requirements & filling capabilities, some almost to zero iirc - read up on the one you are using. Also, best to use a cylindrical loctite not a thread locker. A good way to do it is to turn a few thou under and then put a light knurl on and press together with loctite applied. This leaves a gap if the loctite needs it but positively locates the shaft in the hole and holds it in place while the loctite sets

btw, I see no need to pin in either case, pinning is usuall to keep everything aligned - since you carved from the sold there's no need

 

[compound driver 2]

Hi
I now always silver solder built up crankshafts. Best if you leave all the parts 1/16 over size and then
finish machine as you would for a from solid crank.
Never had one let go since starting using silver solder. That said a pinned and soft soldered crank should be ok if the assembly uses a press fit and tapper pins.

Cheers Kevin

 

[dicej32]

OK, got a little work done on the crankshaft yesterday. Turned the 5/16" shaft and loctited the web/journal to it. I used Loctite 609. It's amazing how strong that joint is! First time user and very impressed. So I need to drill and pin now. I bought some 1/8" dowel pins. These are .0002" oversize which is standard. So do I drill 1/8" or do I drill somewhat smaller? I don't have a 1/8" reamer yet but it would seem with a press fit I could just use a normal drill and just press the dowels in. Any tips?

Thanks,

Jenaro

 

[AllThumbs]

Drilling with a 1/8" bit will get you a hole a few to several thou over. Without a reamer, I would try drilling a hole 1/64" under 1/8", then redrill with the 1/8" drill. That will get you close. I would try it on some scrap first to be sure the hole isn't too big.

Eric

 

[Mcgyver]

the smmaller the nominal dia, the tough it is to do interference fits - working to tenths to get the right interference on a 1/8 hole is a challenge! I can't see why you'd need to pin though....work out the surface area x loctite's tensile strength and you'll see pinning is more than braces and a belt