Re: Tough technical questions

1. The application is to install a rotary shaft oil seal in an aluminum

> housing. The configuration of the seal is with a rubber coated outside > diameter. The fit in the bored housing is a light push fit. I suspect the > seal will work loose on its own during service. What is the best way to > install this seal? Options I've considered include replacing this seal > constructed with a metal o.d., but this is not normally recommended due to > the high coefficient of expansion. A more promising solution is to "glue" > the seal in with Loctite 495, cyanoacrylate adhesive. Will that work? >

Loctite 609 would be a better choice, IMO. 495 is just common super glue, and would probably not be suitable for use on oil seals.

2. The problem is installing a chain sprocket onto a keyed tapered shaft > which is then secured with a retaining nut. What is the best practice: > Install on clean and dry taper, install on greased taper, or apply a high > strength Loctite 272 to the taper before assembly? The idea is to make a > good assembly but be able to disassemble with no more than a puller without > heat. Am I correct in assuming that the key is designed for indexing but > the torque is taken up by the taper?

Yes

If the taper is greased, removal is

easy, but the torque might be passed on to the key and cause localized > stress and failure. Clean and dry I think is the standard way of assembly, > but Loctite application may be in common practice too. >

I agree with the "clean and dry". If you are worried about it loosening on the shaft, you could always heat the sprocket in a pan of water before assy, then immediately torque the nut down. A little 242 on the threads would keep the nut from loosening. H

Reply to
Hairy
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The rubber O.D. seal should be a tight fit. No adhesive is needed. It will stay and not leak. They do it all the time on motorcyles.

Again, nothing is needed. Don't grease. the keyway and taper will hold the sprocket in place. It is the same principle used on the flywheel of mowers. Light pressure and a rap with a hammer should separate them as needed. Hank

Reply to
Ninebal310

I would clean the parts and then add a thin layer of grease. Then torque the bolt to specs. Even with gease, you will need a puller to get the sprocket off. Because it is a tapered press fit the sprocket will still move a bit up the taper.

------------ Alex

Reply to
Alex Rodriguez

I don't have an answer for the specific application, but from a design/engineering standpoint, I would follow the written procedure as far as grease or no grease. I say that because, unless there is a positive stop (a step), the stresses on a tapered fit will go up maybe an order of magnitude or more for the same bolt/nut torque, possibly stretching or breaking the sprocket if it was not designted for that stress (i.e., if it was designed assuming no grease).

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

Reply to
Bill Putney

FYI....."cyanoacrylate" = Super Glue. while superglue bonds a lot of low stress applications, I do not think that the brittle properties of that adhesive will accomplish your desired task.

As far as I know the dry taper and the keyway is all you need. As long as the keyway fits snug into the shaft, part of it's purpose is to prevent rotation.

Reply to
Eightupman

put a little silicon on the outide of the rubber coated seal and then you could pean it in a bit with a punch.....just another option.

Reply to
Scott M

Use the rubber coated ones and the Permatex to help hold it. You will get galvanic action between the steel and aluminum with the non-coated ones. That's why the OEM ones are rubber coated to prevent that corrosion from happening. You don't want the cases to corrode and get pitted in the seal area after time goes by. A 2 stroke motor has retainer plates to hold the seals in as they have pressurized bottom ends, not a problem with a vented 4 stroke crankcase.

Reply to
Repairman

I suppose a seal with a slightly larger o.d. is not available? that would be the ideal option. The seal ought to need to be pressed or lightly hammered in to have any hope of reliable retention.

FWIW the standard practice for dealing with tapered-end rear axles with separate hubs (commonly used on Studebaker, AMC and others) is to install them clean and dry. They require a lot of force to separate when torqued to spec, so no worries there. I have heard tell of people lubing the tapers and subsequently splitting the cast iron hubs.

nate

Reply to
Nate Nagel

Precisely the point I was making.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

Reply to
Bill Putney

Use a thin coat of Permatex clear silicone sealer/adhesive:

It would hold bananas to ice-cream and seal them as well. I use it on cars with problematic intake manifold front and rear seal leaks. A trick from drag racing days, with angle cut heads, and no way to use the manifold sealing strips.

I hope this helps?

Refinish King

Reply to
Refinish_King1

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