The Making of a Full Circle Crank in a Homeshop

[Deets066]

Sweet thread

 

[jmssaws]

1122 crank is in route

 

[SteveSS]

Subbed

 

[Deets066]

So if I understood right, these rings for the crank can be bought?

 

[bikemike]

The merits of using one have been and are beeing discussed in other threads, but here is a thread on how I have been able to use a stock crank, and turn it into a full circle.

I started this one by chucking on the pto end, and indicating to zero runout. A more accurate way would be to use a center in the headstock, and spin the crank between the centers.
View attachment 13204


After its centered, I run the tailstock up and put a little pressure on it. Then find the beginning point of cutting, zero the dial, and take light passes until we get contact on the throw side as seen here. This one only had to have .025 removed.
View attachment 13206


I used crank saver rings on the last one I did, but decided to make some from scratch for this one. I found a piece of old John Deere hydraulic cylinder tube, bored it for an easy slip fit of the crank, then turned down and polished the od. The rings are .025 thick, so with the loose slip fit the assembly will be a bit larger in diameter. Here are the rings getting parted off.
View attachment 13207



And the old crank with new rings slipped onto it.
View attachment 13208



And the crank fitted inside its case, just to see how it would look!
View attachment 13209

I bet it's gunna shake like a mofo. Are you going to insert a fiber filler to it to prevent it from coming apart if a Crack does form.

 

[Deets066]

I bet it's gunna shake like a mofo. Are you going to insert a fiber filler to it to prevent it from coming apart if a Crack does form.

Won't shake anymore than a regular crank

 

[bikemike]

Won't shake anymore than a regular crank

I just figured the counter weight is to balance out the Slug and rod. I have 2 China engines that have full circle cranks and they shake like crazy. No balance drilled out unlike motorcycles wich run smoothly

 

[awol]

In my mind it would affect the balance a bit, but just by holding the saw its not noticeable. It may have helped that the piston I used was much lighter than a stock one.

 

[Deets066]

We've got into this subject before about balance and harmonics. It's very interesting and confusing to me

 

[Deets066]

Rpm is the key

 

[WKEND LUMBERJAK]

Deets sounds like he has lots of RPM's

 

[Mastermind]

I spin at about 400,000 RPM in my head most days........and I don't sssshhhhhhhaaaaaaaakkkkkkkkkeee much.....

 

[tree monkey]

http://s155.photobucket.com/user/scottk66/media/dadssawparts001.jpg.html?sort=3&o=119

440 crank I did years ago. notice how thick the ring is

 

[awol]

Hmmmm, I wonder if mine is gonna be strong enough? I'll make J's a little thicker just to be sure.

 

[tree monkey]

http://s155.photobucket.com/user/scottk66/media/dadssawparts010.jpg.html?sort=3&o=128

this is not the case I used, but I bored the case to clear the crank. the case was not centered to the shaft to start with. this allowed for a much tighter fit

 

[jmssaws]

Won't shake anymore than a regular crank

I agree, I doubt there will be any difference in vibs,may smooth a 66 out some.

288 piston is heavy but i can lighten it to oem weight.

 

[David Young]

http://s155.photobucket.com/user/scottk66/media/dadssawparts001.jpg.html?sort=3&o=119

440 crank I did years ago. notice how thick the ring is

I remember that build scott, I would not have known it was yours

 

[awol]

So if I understood right, these rings for the crank can be bought?

A product called "crank saver" sleeves is produced by National, thats purpose is to slip over end of crankshafts and cover the groove the seal left by thousands of hours of rotation. The first crank I did used these sleeves, but since I got the old Atls dialed in I will just make them myself!

 

[DSS]

A product called "crank saver" sleeves is produced by National, thats purpose is to slip over end of crankshafts and cover the groove the seal left by thousands of hours of rotation. The first crank I did used these sleeves, but since I got the old Atls dialed in I will just make them myself!

Also known as a speedi sleeve

 

[Sty57]

This is SO over my head but, can someone explain why your doing this?

Wouldn't adding weight to the crank put more drag on the rotating assembly?

On a 4-stroke you always try to lighten the rotating assembly to make it Rev faster.