Thermal distortion compinsation

[alansimpson]

I have a mechanical instrument comprising a polycarbonate frame about 120mm and wheel 100mm dia mounted on miniature ball bearings. I am running into difficulties with thermal distortion causing extra friction on bearings. I am looking for design guides to minimise or compinsate for thermal distortion.
Any help would be apprecisted.

 

[diskullman]

This is one of the many uses for tolerance rings

http://www.usatolerancerings.com

Russell Giuliano

 

[Heckler]

What process method is this PC wheel manufactured? If molded is it unfilled or filled? Molded PC shrinks linear .003 - .0075 in/in. What is the operating temperature of this instrument? Thermal expansion (CTE, linear 20°C) is 17.8 - 66.7 µin/in-°F.

Check

http://www.matweb.com

for you specific PC.

Heckler
Sr. Mechanical Engineer
SWx 2007 SP 3.0 & Pro/E 2001
XP Pro SP2.0 P4 3.6 GHz, 1GB RAM
NVIDIA Quadro FX 1400
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(In reference to David Beckham) "He can't kick with his left foot, he can't tackle, he can't head the ball and he doesn't score many goals. Apart from that, he's all right." -- George Best

 

[MikeHalloran]

Conjecture: The housing in in two halves, like a clamshell, with a bearing in each half. The friction arises because the bearings become more misaligned with temperature.

Response if conjecture is correct: Make one half just a cover, but both bearings in the other housing half, so their temperatures track each other and they are naturally aligned. You will probably have to destroy the symmetry of the wheel, too, offsetting the web to clear the bearing housing.

Response if conjecture is not correct: Tell us a little about the problem, already.





Mike Halloran
Pembroke Pines, FL, USA