David Jenkins
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| posted on 22/1/09 at 08:28 PM |
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Rotary seal for a variable gap?
I have a "challenge" in my current project for the Locost.
I want to provide a seal between a stationary shaft and a rotating metal plate that fits over it. The plate will be rotating at up to a few hundred
RPM.
The following crummy picture may or may not explain what I mean:
 
rotary seal
The difficulty is that I cannot guarantee that the hole in the plate will be concentric with the shaft all of the time - it may be 1mm +/- 0.2 mm -
and the distance between the face of the shaft's thicker section and the place may also vary 2mm +/- 0.5mm.
I want the seal to keep out dust and dirt, and maybe the occasional bit of moisture - I wouldn't expect it to keep out significant water
though.
The best suggestion I've had so far is a well-oiled leather or felt washer between the shaft face and the plate.
Anyone got any other suggestions?
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madteg
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| posted on 22/1/09 at 08:55 PM |
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[Edited on 22/1/09 by madteg]
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David Jenkins
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| posted on 22/1/09 at 09:06 PM |
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quote:
Originally posted by madteg
Oilite thrust washer
That wouldn't cope with the variable gap, would it?
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madteg
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| posted on 22/1/09 at 09:08 PM |
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What size gap min to max.
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DIY Si
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| posted on 22/1/09 at 09:25 PM |
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I'd probably go for a felt seal. That or a close fitting bush/washer and a spring behind it to allow for movement?
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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David Jenkins
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| posted on 22/1/09 at 09:35 PM |
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quote:
Originally posted by madteg
What size gap min to max.
Uncertain! (I'm still at the planning stage)
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paulf
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| posted on 22/1/09 at 10:07 PM |
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I would use a V seal, it is a soft rubber seal that can seal on the face as well as shaft.
Paul.
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David Jenkins
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| posted on 22/1/09 at 10:16 PM |
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The V seal looks ideal - I've just done a bit of googling, and they seem very suitable...
Thanks!
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Meeerrrk
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| posted on 22/1/09 at 10:27 PM |
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2nd v-seals. also use at work t-seals. much of a muchness. they are your best bet.
to be honest, regardless of what you use, you should try to get it as concentric as you can (i know you already know this, just stressing the point).
The better it is, the more likely it will seal 100%.
regards
MArk
For Sale : 2008 Aries/Stuart Taylor Motorsport Locoblade (954 Blade)
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02GF74
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| posted on 23/1/09 at 08:24 AM |
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3rded - seals.
just feed it lots of fish and tell it to keep hold flippers tightly together.
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David Jenkins
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| posted on 23/1/09 at 09:07 AM |
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^^^ 
I was cautious about the concentric bit - in almost every case it will be concentric give or take a thou - but I couldn't guarantee it. I will
be trying hard to make it so, though!
I presume that I can get these seals from any decent bearing supplier - is that a reasonable assumption?
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DarrenW
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| posted on 23/1/09 at 11:49 AM |
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can you get a bearing to fit on the shaft then secure the plate to the OD of the bearing (i havent thought how yet). That way you will get the seal
that the bearing comes with and something to help get the plate a bit more concentric.
I have a couple of bearings on my desk that you can have to play around with.
maybe the 1mm plate but can be a tightish fit on the OD of the bearing and secured with some JB weld etc.
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carpmart
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| posted on 23/1/09 at 12:16 PM |
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What about the type of seal used on wiper motor stems where the exit the bulkhead?
I think they would work pretty well for your application!
You only live once - make the most of it!
Radical Clubsport, Kwaker motor
'94 MX5 MK1, 1.8
F10 M5 - 600bhp Daily Hack 
Range Rover Sport - Wife's Car
Mercedes A class - Son's Car
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David Jenkins
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| posted on 23/1/09 at 12:39 PM |
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I have a couple of bearings with seals - but the v-seals look like they will cover all the requirements.
All I have to worry about now is finding a supplier! Ipswich has 2 good bearing suppliers and another that's excellent for o-rings, hydraulic
fittings, etc. (Pirtek) so I hope I'll be OK.
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