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teenix · (This post was last modified: 12-21-2021 02:24 AM by teenix.)

Hi all,

I've repaired a few gummy wheels now and I am starting to get convinced the 1/4" outer diameter o-rings are not quite the right ones to use.

I may have missed this earlier on, but I am finding that when these are fitted, the o-ring outer edge butts up against the little nylon idler roller and causes drag on the drive wheel.

If you make a repair with o-rings, then it is best to check how well the drive wheel turns without the motor installed and with no card in the slot. If it doesn't spin freely, then it is likely the o-ring diameter is too great. The drive wheel should slide into position without drag either, or the o-rings are too wide.

I tried some 3mm silicon tubing but this is just a fraction too small although it works on maximum pressure adjustment.

Looking around, there are some o-rings with 2.57mm hole and 6.13mm outer diameter. This is somewhere in between 3mm and 1/4 inch. These look like they are easily available, bags of 50 for a few dollars.

I also came across an old post which mentioned the same thing, so maybe there is something in this, although I am yet to try them.

https://archived.hpcalc.org/museumforum/...50207.html

Its interesting that the inner o-ring on the repaired wheel is almost useless. It doesn't look like it touches the card, but it does serve as a spacer for the outer one :-)

cheers

Tony

GreyUser · 12-21-2021, 04:33 AM

The dimensions referenced in that post are the dimensions of US o-ring size 005 which has been documented countless times on this forum.

teenix · 12-21-2021, 05:47 AM

(12-21-2021 04:33 AM)GreyUser Wrote: The dimensions referenced in that post are the dimensions of US o-ring size 005 which has been documented countless times on this forum.

Ok, I didn't know that - live and learn :-)

cheers

Tony

GreyUser · (This post was last modified: 12-22-2021 03:39 AM by GreyUser.)

Worth a note that I saw an early post from Tony Duell that mentions the US size 005 is the same as BS 005. Might that size be available in AUS?

teenix · 12-22-2021, 04:18 AM

(12-22-2021 03:38 AM)GreyUser Wrote: Worth a note that I saw an early post from Tony Duell that mentions the US size 005 is the same as BS 005. Might that size be available in AUS?

I'm not sure, I haven't heard of those sizes. I can get the 6.13mm from RS Components cheaply except for postage.

cheers

Tony