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HelicopterMain Discussion › Buying bearings? I don’t know what to ask for
09-02-2003 02:54 PM  14 years agoPost 1
Mr H

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Perth, Australia

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Ok I haven’t bought bearings before but I need a front bearing one for my Raptor 30 (TT36 engine) to replace the leaking one. I don’t have a diagram of the engine. And as I haven’t bought bearings before I’m not quite sure what to ask fo.

What size (eg how are they measured), quality, what speed considerations should be considered?

However I believe I do need a sealed bearing (woo I know something)

Any advice is appreciated

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09-02-2003 03:25 PM  14 years agoPost 2
JuanRodriguez

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The Villages, Florida

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Mr. H,

Your front bearing is not a "sealed" bearing.... It has a shield on the side facing out and is open (for lubrication) on the engine side of the bearing.... The best thing to do is to pop it out and take it to your local bearing shop and let them match it for you.

Second option......I did a quick search for you and found the TT part number and it appears to be for BOTH front and rear bearing. Part number is PN0040. Unfortunately, they do not provide the dimensions of the bearing, that would be too easy......Your local hobby shop in Australia should be able to order them for you......

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09-02-2003 04:35 PM  14 years agoPost 3
Mr H

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Perth, Australia

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Thanks for the feedback

When I referred to a sealed bearing I was under the impression that the outside face of the bearing was sealed (or sealed to a different extent than the original), this is what I assumed would fix the current leak. I understand the inside is open for lubrication.

Is that correct?

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09-02-2003 05:32 PM  14 years agoPost 4
Allora

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North East, NJ

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Sealed vs Shield

When I referred to a sealed bearing I was under the impression that the outside face of the bearing was sealed (or sealed to a different extent than the original), this is what I assumed would fix the current leak. I understand the inside is open for lubrication.
A Sealed bearing is a little different that a Shielded bearing. A sealed bearing side will actually have a oil tight rubber seal between the edged of the inner and outer race. The shielded bearing, which is what it sounds like you have, is made up of an interlocking metal cover, or Shield. It is generally used just to keep the balls and keepers clean, and are not good at holding back oil.

Check out this page from http://www.bocabearing.com:

http://www.bocabearings.com/hobby/index.htm

I've never used them, but I'm sure if you call them up they may have already sized a bearing for your application. They say on that page they can also size one based on your TT part#. I'm not sure about shipping thought.

Good Luck!

-Lou

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09-03-2003 10:44 AM  14 years agoPost 5
donlynn

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New Zealand

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Gidday H

front bearing is a 699Z (the Z means single metal sheild)
Rear bearing is a 6901, you can use a 6901 2rs which means 2 rubber seals and pick the seals out the wash the bearing in methanol to remove the grease as these bearings are way more common.

To replace the bearings the no stress way,
Heat the crankcase in the oven to about 120-150 degrees C for 20 minutes then remove and rap sharply on th cooks chopping board while she is out, allow the crankcase to cool slowly at room temp then cleanm the bearing housing area untill spic and span as the cleaner this is the better the heat transfer away from the bearings with a increase in life. then heat the crankcase to 120-150 again fore 20 minutes then remove anfd fit the room temp bearings with a appropriatly sized clean tube socket, have a dry run as you get one shot while the case is hot before it shrinks again .
oil the bearings and conrod ends with a couple of drops of neat glow oil before fitting back plate .
did you try minature bearings aussie ? you'll find $25 willl buy both, get 2 sets while your at it so you have a spare for ron.

The sheilded bearing xxxxZ is used as against the sealed xxxxRS/ 2RS(one rubber seal / 2 rubber seals)
as the sheild creats less drag on the bearing as it is not in contact with the inner race therefore less heat or burning of the seal lip therefore the sheilded bearing has a higher speed rating= less drama for the engine manufacturer but higher maintenance.

Regards Don

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