Crank jig for pressing on bearings?

Totally normal JBOT /

So now that I finally got my hydraulic press working again,

I'm going to no longer have to heat up bearings to get them on.

My question is this.

If I want to press bearings onto each side of the crank,

I'm assuming I should make a jig that would go between the lobes, to suspend that side of the crank so there's no stress on the center pin.

My question is if anyone has such a jig I can get some ideas from.

Thinking of using 2 pieces of angle iron, sandwiched between the lobes with a cut out for the conrod.

Thoughts?

Re: Crank jig for pressing on bearings?

Totally normal JBOT /

Thinking that putting the bearings in the cases first might be better with this tool since the press fit between the crank and inner bearing races have a looser tolerance than the outer race/cases tolerances. Easier to get together that way with no heat? Think so.

Re: Crank jig for pressing on bearings?

I would press the bearings into the case first, then pull the crank into the bearings.

Re: Crank jig for pressing on bearings?

Totally normal JBOT /

You have a jig that you use to pull the crank in?

Re: Crank jig for pressing on bearings?

No, but I've seen them.

I just heat the inner bearing race with a hot piece of round stock and it slides in.

I've made my crank slip fit (more like push-hard-fit) in the bearings on the spx.

Re: Crank jig for pressing on bearings?

Heres a crank puller tool:

http://www.dansmc.com/split_crankcase.htm

Re: Crank jig for pressing on bearings?

Totally normal JBOT /

I see, so a metric coupler between the crank and some all thread?

Re: Crank jig for pressing on bearings?

That crank puller is cool but the argument for setting the brgs on the crank first and then the crank w brgs in tha case last is because the bearing to crank fit is steel to steel where its steel to aluminum in the case. Aluminum expands more than steel with heat so Its the easier fit. I am sure you already heat the cases to 250-350F before bringing them together?

Re: Crank jig for pressing on bearings?

I've done both bearings in case first, and on the crank first, both equally easy with heat. But if you're not going to heat anything, I would press the bearings into the case first, then pull the crank into them.

Re: Crank jig for pressing on bearings?

Re: Crank jig for pressing on bearings?

Totally normal JBOT /

Thx, that's what I figured.

So is there a "best" way to do this?

I can either pull the crank in to the cases with bearings already pressed in like Alex said, or heating cases to allow the crank and bearings to just pop in.

What's your technique?

I've always used heat in the past.

Re: Crank jig for pressing on bearings?

No idea what's best...

A nice trick I saw somewhere was to install the crank and bearing in one case half, then slightly preload that side with the puller, before you tap the other case half with bearing installed on. That way when you release the puller there would be no "binding".

Re: Crank jig for pressing on bearings?

just so long as you're not pulling across the bearing... that press tool photo above looks like it is pulling the crank and holding the case, that would be a no-no.

my crank web pressing holder tool that i use for pressing crankshafts apart/together, is just a slab of steel thin enough to fit between the webs with a notch cut in it to pass it around the big end of the con rod. its pretty simple, you could make it with an angle grinder if you had to, i'm sure there are better ways to do it, thats just what i had handy.

Re: Crank jig for pressing on bearings?

Charles Cole (OFMC) /

Yeah, Just look at the pic of the tool on Treats & duplicate it. We know you got the skills!

Re: Crank jig for pressing on bearings?

Totally normal JBOT /

I already made one like that. Just kinda sucks

I got the plans now.

Re: Crank jig for pressing on bearings?

on yespas and pugs i put the bearings in the cases then heat up the case and bearing combo along with freezing the crank then assemble.

although i have noticed when i do it that way the crank sometimes feels like its in a bind so i tap on the case with a leather mallet and it pops which i assume is the bearing fully seating on the crank lobe because then its as smooth as butter.

it seems like no mater how hard i try if i do it the other way the case cools too fast and then the bearing gets cocked and stuck.

Re: Crank jig for pressing on bearings?

I made a puller to pull the crank into the cases. There are plenty of reasons the bearings should be in the case first. Most people do not shim their cranks, so there is no way to tell if your bearings are flush and square when you put them on the crank first and then press the cases on.

Plenty of people get away with it and don't have problems, but its not ideal and more susceptible to error.

Re: Crank jig for pressing on bearings?

Hmm... that is interesting.

I've noticed most OEMs (tomos, peugeot, honda) sell the cases- oe replacement- with the bearings installed, making me think there is a reason for that.

my guess was that it is easier at the factory to put the seals and bearings in the cases first with a press, and do the crank later. The big problem i see with those factory tools is that they are pulling across the bearing itself. Might be OK for german bearings running at low RPM but i just try to absolutely not ever put pressure across the bearing itself in any motors i build.

my instinct (and the way i've always done it) would be to put the bearings on the crank first because the aluminum expands more and its much easier to ensure they are seated on the crank rather than ensuring they are seated in the aluminum cases. I would think you would want them to seat on the crank fully and if they have to float, let them float in the case.

plus having more expansion in the aluminum gives you more wiggle room to put the case on with the bearings in situ on the crank, if you are trying to put the crank into the bearing in the cases it is harder to keep everything aligned.

Usually my method is to put both bearings on the crank first, then do one case half, then cool the case half and crank together, apply the gasket or sealant to the cool half so it doesn't start to gum up prematurely, then apply the other hot case half.

I've had way more bearings stick to cranks while dropping them on, than bearings stick into cases... the only cases i ever have trouble with are minarelli and garelli because you have to get all that stupid pedal gear junk aligned before final assy.

usually with those spaghetti motors i end up having to do a slight re-heat of the bearing race area with a bernz-o torch and a couple light taps with a rubber mallet to free everything up.

Re: Crank jig for pressing on bearings?

Totally normal JBOT /

What about motobecane motors where the seal has to be in before

putting the cases together? For hobbits I usually heat soak the cases in the oven at 325 for 20 min. Can a seal take that heat?

Re: Crank jig for pressing on bearings?

I usually do it that way on the pug cases, no seal problems so far.

Re: Crank jig for pressing on bearings?

yeah i think viton seals are good to about 400 before they get shitty

i mean, you look at the side of some engines running full tilt, they'll get that hot fo sure.

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