Keefer

My Feedback: (2)

Happy New Year and all that!
So, I've got some bad bearings in my Saito 91, and started disassembly. I've attempted to pull off the prop hub using a gear puller, only to start pulling metal off the hub!

The case was heated to 300F for 30 minutes, and no luck. I've also tapped on the end of the crank, but I don't think I'm going to win against this prop hub AND the bearings.

Can I go to a higher temp? Would a three-armed gear puller work better?

liquid_TR

You seem to have a puller with a very little leverage. Use one with a bigger claw (wider)

You actually dont need to heat up the case at all. If puller grabs it right, drive hub pops right off with a (proper) little pull.

I normally use a huge battery terminal puller, without even scratching the hub.

rcdude7

My Feedback: (264)

If you have a heatgun, use it to heat the prop driver while you have the puller on it and tightened so it is preloaded. When the prop driver expands from the heat, it will "pop" right off.

I do this, and it works for me every time.

Mike

proptop

My Feedback: (8)

I use a Propane torch and concentrate the heat directly on the prop driver...you gotta get them pretty doggone hot. (sometimes, the residual oil will smoke )
Then give the end of the puller screw a quick rap w/ a hammer.

I have one of those pullers, and the jaws flex quite a bit, so (before I got a better one ) I used a large worm screw type hose clamp wrapped around it, tightened to keep the jaws from slipping off.

DarZeelon

Keefer,


You got it all wrong!

You must not heat the crankcase in the oven (or with a torch), before it is completely disassembled and the only thing left inside it are the bearings!


Removal of the prop-driver is one of the things you must do, with the crankcase still cold.

I copied this from another thread:

----------------------------------------
When using a puller to remove a very tight prop-driver, 'install' it with a good deal of pre-load (tighten the bolt firmly)....
...And then heat the prop-driver with a propane torch - the prop-driver will pop off audibly.
----------------------------------------

[link=http://www.rcuniverse.com/forum/m_6837788/anchors_6840500/mpage_1/anchor/tm.htm#6840500]This is the thread[/link].


After you have removed the prop-driver, the crankshaft and everything else, then you must heat the crankcase in the oven, in order to remove the bearings from it.

rainedave

My Feedback: (1)

A few times I have heated cases in the oven in order to remove sleeves that were "welded" in with castor varnish. Dar, are you saying that this is something I shouldn't be doing? When I've done this the only parts that were still in the case were the sleeve and bearings.

David

w8ye

My Feedback: (16)

The main problem here is that you are trying to use a faucet handle or battery terminal puller on a Saito hub.

You need a puller with more power and a better way to grip the hub.

DarZeelon

No, Dave, this is not what I am saying...

When your objective is replacing the bearings and you have the crankshaft still installed in the crankcase; heating the crankcase and then removing the crankshaft, will have it come out with the rear bearing still installed on it; not in the crankcase. Removal of the bearing will be much more difficult then...


With any Saito, the 'jug' comes off by removing the four bolts at the bottom, that connect it to the crankcase... There is no separate sleeve as such, so your example does not apply.

I also use the method you stated to remove a stubborn sleeve...

Keefer

My Feedback: (2)

Thanks, all!

w8ye - What is the top component in your pic? I've seen those labeled as "bearing separators", however I don't see how it would work on the prop hub.


DarZeelon - so you agree that heating the prop hub will expand and free it? I'll try the Rossi thread suggestion. It makes sense. But like rainedave suggests, I've had to heat the entire case to get the drive shaft free of the bearings. How do you get the drive shaft out?

w8ye

My Feedback: (16)

It is indeed a bearing separator. Use it to grip the groove in the Saito prop hub. Then attach your real gear puller to the bearing separator. Do not make the bearing separator tight. Just close it enough to place the flange within the groove.

There is no gear puller that is going to stay in the Saito groove unless it is one that has a retainer ring around three fingers. Even these will scratch your hub.

Some Saito hubs are really tight. It is unlikely you will be successful in getting one off with a faucet handle puller like was shown in the first picture.

liquid_TR

The puller I used was this one. It has huge claws (around 1.5 cm) and its heavy! (~1.5kg) The claws can be rounded with a dremel tool to fully grab the hub groove - although i didnt find that necessary as the hub poped out with the huge leverage of this puller.

DarZeelon

Quote:

ORIGINAL: Keefer

DarZeelon - so you agree that heating the prop hub will expand and free it? I'll try the Rossi thread suggestion. It makes sense. But like rainedave suggests, I've had to heat the entire case to get the drive shaft free of the bearings. How do you get the drive shaft out?

Keefer,


First of all, it is a crankshaft; not a drive-shaft...

Heating the crankcase will not get the crankshaft out...

This heating technique is used to remove the bearings from the crankcase (or the prop-driver off the lock-cone), since aluminum has a greater expansion coefficient than steel, or brass. So, when the assembly is heated these items' fit becomes looser.

Heating the steel bearings with the crankshaft inside would do nothing, since the bearings' steel will expand as much as the crankshaft's steel.

The crankshaft is normally a sliding fit in both bearings. I.e. the interference fit is to a very small degree.

After the prop-driver is off (and the con-rod - nothing is between the rear of the crankshaft and the air...), finger force, or holding the crankcase and pressing the front end of the crankshaft against a piece of wood, should be enough to get it out.


If the crankshaft comes out with the rear bearing on it (after heating the crankcase before removing it...), the easiest way to get the bearing off is to heat the crankcase again, reinstalling the crank+bearing assembly in it, letting the assembly cool down completely and removing the crankshaft alone...

If you did not do it right, just reassemble and do it right...

jessiej

Very clever idea, proptop. Now that you have broached the concept I can think of a number of uses, some involving model engines and several in other areas. Thanks!

jess

blw

My Feedback: (3)

Those alone will sometimes work, but most of the time you need to do it like W8YE advised. Some Saitos drive washers are so tight that they release with a loud bang.

I have a friend who got his bearings out of a 2 stroke without heating anything or using a puller. The new ones dropped right back in without heat too. He got lucky.