Bearing holders

Bearing holders

Post by mgran » Tue, 10 Feb 2004 08:06:38


I've been giving some thought to bearing holders lately and I have some
thoughts/questions that perhaps someone can comment on.

It seems that, by far, the most popular type of bearing holder is a two
piece (main cap?) style.  This is where the upper part of the bearing
holder is attached to the end of the fork leg and the lower part of the
bearing holder attaches with screws/bolts to the upper part thereby
clamping the bearing in between.  

The problem that I see is that if you over-tighten the bearing holder
you run the risk of damaging the bearings.  If you under-tighten the
holders then you run the risk of them falling off or at the verly least
having a wobbly wheel.

One way to address this is to press-fit the bearings into a holder and
then figure out how to attach that to the frame.  I believe Pashley,
Miyata, and some cheap taiwanese unicycles use this method (with varying
degrees of success).

So, what if you combine both?  A split holder with a lip on the inner
and outer edges that when tightened completely (the bottom comes into
contact with the top) holds the bearing just right.  With this type of
holder you would not need to worry about over-tightening since any
additional tightening would not put more pressure on the bearing.  It
would simply put pressure on the threads of the screws.  It would make
the process of much simpler since you would not need to use a subjective
measurement of what is "tight enough".   And, because you could securely
tighten the screws you would not need to worry that they might come
loose while riding.

I also have a question regarding the bearing holders on the KH series
(and Summit) frames.   They are nearly twice as wide as is necessary to
encompass a bearing.  Nearly half of the width is not in contact with
the bearing.  And, the bearing is not centered in the holder (it sits
slightly to the inside).  So, the questions is:  Why not have the
bearing holder narrower?  An why put the bearing off-center?  When I
tighten the bearing holders on both the Summit and KH24 I find they have
a tendency to pull the lower part to the outsite since there is nothing
there to hold the top and bottom apart.

I'm interested to know if anyone has build a bearing holder (or frame
that uses them) that addresses the above mentioned objections?

-mg

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Bearing holders

Post by U-Tur » Tue, 10 Feb 2004 08:18:01

The GB4 and Hunter frames have a real nice main-cap which encircles the
bearings, so that if you do overtighten, it does not deform the bearing
the way the cheaper main caps do.  See 'this photo'
(http://tinyurl.com/2z3gd) for example.  However, a torque setting of 40
inch-pounds seems about right for them.  This setting seems to the hand
to be not very tight, but it works quite well.  These holders have a lip
on the outside only, which is easier to machine and seems to work
well.

"securely tighten" tends to mean "lean on it until my weight won't turn
it any more", which is usually overkill for uni parts.  Go for "snug but
not too snug" together with some blue loctite and you'll save a lot of
parts.

For the Summit and KH try not tightening the holders as much.  Use
loctite on the threads so that you know you don't have to to tighten
them a lot for them to stay put.  You may also have to put a slight
inward angle to the frame arms, however, that is not ideal.

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Bearing holders

Post by forget_your_lif » Tue, 10 Feb 2004 09:02:43

Quote:

> *See 'this photo' (http://tinyurl.com/2z3gd) for example.  *

i dont like those "shaft collar" style holders because of one
reason.this may be hard to explain but i'll try.on the bottom part,the
cap,the part not attached to the frame,the bolt head is counter sunk
into the holder and it leaves only a paper thin bit of medal separating
it from the bearing on the other side.

over time and tightening a crack can develop in the thin spot.this
happened on my 1st MUni,my Profile.i had to send Profile 12 dollars for
a couple of spares.not a super big issue it did happen to me.UniBrier
has that uni now and the spare caps,maybe he could post a pick of the
cracked one.....

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Bearing holders

Post by U-Tur » Tue, 10 Feb 2004 09:13:55

Quote:

> *i dont like those "shaft collar" style holders because of one
> reason.this may be hard to explain but i'll try.on the bottom part,the
> cap,the part not attached to the frame,the bolt head is counter sunk
> into the holder and it leaves only a paper thin bit of medal
> separating it from the bearing on the other side.

> over time and tightening a crack can develop in the thin spot.this
> happened on my 1st MUni,my Profile.i had to send Profile 12 dollars
> for a couple of spares.not a super big issue but it did happen to
> me.UniBrier has that uni now and the spare caps,maybe he could post a
> pick of the cracked one.....

> edit:forgot the word \"but\"   *

Was this a Profile unicycle, Jag?

--
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Bearing holders

Post by showar » Tue, 10 Feb 2004 10:48:32

I made some bearing holders that were an attempt to solve the problems
that Michael described.  The bearing holders are on the stainless steel
frame that Paco has and there's pictures 'here'
(http://www.unicyclist.com/gallery/albun90).

Machining a lip on both sides of the holder is a pain so on these I
bored from one side leaving a lip on the back but I bored them to a
depth that would work out to turn the lower half around.  That puts a
lip to the outside on the top part and the lip to the inside on the
bottom part thus capturing the bearing with lips on both sides.  Also,
they were bored to give the proper press fit on the bearings when
tightened.  Unfortunately I don't have a piture of the bearing holders
assembled with the top and bottom lips on opposite sides of the
bearing.

I don't know if Paco has the bottom halves turned around now ... come to
think of it, I don't know that I ever told him that the bearing holders
would work that way.

Paco - you've had the frame for a while now.  Any comments?

SH

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Bearing holders

Post by forget_your_lif » Tue, 10 Feb 2004 10:52:56

Quote:

> *Was this a Profile unicycle, Jag? *

yep.

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Bearing holders

Post by forget_your_lif » Tue, 10 Feb 2004 10:52:56

Quote:

> *Was this a Profile unicycle, Jag? *

yep.

--
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Bearing holders

Post by Jim_Ro » Tue, 10 Feb 2004 14:59:34

I have solved the problem of having the bolt too loose by using Grade 8
aircraft bolts with pinch nuts (Nyloks work too). The added advantage of
this is that you can adjust the straightness of the wheel in the frame
to a small degree by the tightness of the bolts, and the won't come
loose.

--
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TTFN

JR
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Bearing holders

Post by paco » Wed, 11 Feb 2004 01:14:08

Quote:

> *Paco - you've had the frame for a while now.  Any comments? *

So far, I love the bearing holder style.  Every once in a while the
bearing holders come loose, but I just tighten them again.  They have
never slipped, never pinched the bearings.  I've never had any problems
with the wheel being loose in the frame, even during hard MUni.  And I
love the fact that I don't have to worry about getting the tension
correct.  Just tighten them until they're snug, and they are ready to
go.  Plus, I think they look cool as one solid disk of steel.  Overall,
I think it's a very good design.

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Bearing holders

Post by UniBrie » Wed, 11 Feb 2004 03:04:51

Quote:

> *UniBrier has that uni now and the spare caps,maybe he could post a
> pick of the cracked one.....*

The cracked one? Is it still on the frame? Sabin has it out on loan for
a while so I don't have access to the uni.

Here is a pic of the spare bearing caps:

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Bearing holders

Post by Telluride » Wed, 11 Feb 2004 06:45:29

The reason that most uncycles dont have presision fit to the main cap
style bearing h

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Bearing holders

Post by gmoor » Thu, 12 Feb 2004 12:26:43

Shouldered both sides, aluminum.  As has been stated extra machining
hassle is involved.

http://www.unicyclist.com/gallery/album27

Cheers, Greg

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Bearing holders

Post by U-Tur » Thu, 12 Feb 2004 12:43:42

Quote:

> *Shouldered both sides, aluminum.  As has been stated extra machining
> hassle is involved.

> http://www.unicyclist.com/gallery/album27

> Cheers, Greg *

That is such an amazing uni.  I know you have a 26" on it, but what's
the total weight?

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Bearing holders

Post by gmoor » Thu, 12 Feb 2004 12:53:36

Quote:

> *That is such an amazing uni.  I know you have a 26" on it, but what's
> the total weight? *

Thanks Dave,  it has served me well.  I'm not sure of the weight. Tried
to  get an idea with a bathroom scale once and gave up. I know it seems
a helluva lot lighter without the DH tube  :-0

Cheers, Greg

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