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Markku
Unregistered
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 Posted Thursday, April 11, 2013 @ 06:28 AM
Hi All
This trim cable friction problem has been discussed earlier also, but I found a rather good way to solve the problem, which is familiar to most of us.
Here is the system:
I made a fluid and pressure tight plug around the cable (epoxy), (might be also done with a vulcanized tape or similar)
After the epoxy plug was hardened , I installed a bicycle tube (with a valve) in the end of the cable, other end connected around the epoxyplug, and the other end with a wood plug
First I filled the tube with a solvent to clean the cable, the fluid level should be above the metal part cable, and take care, that the cable end is free to move back and forth.
Then plug the free end of the tube, and pump some pressure into the tube. Move the cable from cocpit end back and forth, and check now and then that there is pressure in the tube. It took some 10-15 min to get the solvent trough the line, and the friction reduced dramatically (reduction about 80-90% in my case). I will lubricate the line with thin oil with that same system.
[Edit by Markku on Thursday, April 11, 2013 @ 06:35 AM]
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Bob Grimstead
Unregistered
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Posted Thursday, April 11, 2013 @ 10:47 PM
What a magnificent idea Markku!
What solvent did you use?
Acetone perhaps?
...and I am interested to know how you will get that epoxy off the cable afterwards.
It is an extremely good idea to make that cable as smooth and friction-free as possible.
If you don't, the teeth will strip on the small brass cog in the trim lever.
A replacement cog (only the cog) is now more than £100 (130 Euros?)
Yours, Bob
[Edit by Bob Grimstead on Thursday, April 11, 2013 @ 10:50 PM]
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Markku
Unregistered
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Posted Friday, April 12, 2013 @ 02:05 AM
Hi Bob and others
I used lamp kerosene (I had it a 10litre canister in my garage for my boat heater), I think most of the oil based solvents work fine, acetone might be too agressive and it might cause problems if it dries the cable too much.
I built the sysytem last week-end and I used the material which was available. There should be easier way to make the tight plug around the cable, few rounds of vulcanized tape might be one alternative.
I know it's not easy to take that plug away, but the result is woth of that extra work.
The system might be even better if you put that tube inside a proper diameter plastic or metal tube (make opening for the valve), then you can increase the pressure.
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Jorgen
Unregistered
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Posted Friday, April 12, 2013 @ 03:28 AM
Thanks Markku,
that's an ingenious idea to SOLVE a problem I think we all have felt a sting of bad conscience about. Thanks for sharing!
I get your Point on increased pressure, but maybe it's wise to let the solvent/oil take it's time to run through. If you have a wear and hole in the Cable sheath you don't want too much goo run into the fuse.
By the way, what can be seen of that RF 4 in the background sure looks good. Keep up the good work!
May the 4's be with you/ Jörgen
[Edit by Jorgen on Friday, April 12, 2013 @ 04:21 AM]
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Markku
Unregistered
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Posted Friday, April 12, 2013 @ 03:58 AM
Thank's Jörgen
The project is proceeding unfortunately slowly, but proceeding anyway. I will update the situation with some pictures soon.
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Donald
Unregistered
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Posted Friday, April 12, 2013 @ 02:52 PM
I think kerosene would be an excellent cleaner. White spirit, I imagine, would be a good second choice as it is not aggressive but is very good at moving oily mess along.
Will you follow the clean with a lubricant and, if so, what?
When I bought the RF3 the trim cable was very stiff and the little brass gear wheel was missing a couple of teeth so I've done this too. My method was similar but much cruder without epoxy or pumped pressure. Just an aluminium foil cone wrapped round the cockpit end of the cable clamped end upwards. Electrical tape to seal, lubricant into the cone and patience plus working the cable inner back and forth.
I like modern bicycle lubricants which can be got with added TEFLON and which dry to a film, so it stays in place and doesn't make a mess.
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Jorgen
Unregistered
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Posted Friday, April 12, 2013 @ 03:14 PM
Markku,
I noticed you don't seem to have a shortage of clamps ;) Have you actually counted how many clamps you have in your collection now after this quite extensive woodwork project?
I agree Donald, a teflon additive seems like a good choice. I've had some good results with WD 40 as a cleaner, but maybe Kerosene is cheaper if you need a larger volume.
May the 4's be with you/ Jörgen
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Bob Grimstead
Unregistered
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Posted Saturday, April 13, 2013 @ 00:31 AM
Thanks for all that advice guys.
Being impatient, I was thinking of the strongest solvent, but you're right, something more gentle would be better.
I love molybdenum disulphide. Like teflon, it stays and keeps lubricating after any oil may have evaporated or hardened. So I may try lubricating that cable with my normal engine oil: Castrol 20/50 with moly added.
For the little brass cog wheel I will use grease with moly, easily obtained.
The only drawback is that it is black, so you need to clean it up thoroughly.
Yours, Bob
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Donald
Unregistered
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Posted Saturday, April 13, 2013 @ 03:03 AM
Bob, if you're looking for the strongest solvent then MEK or toluene but I wouldn't put them near a sheathed control cable, or paintwork, for I think any plastic layers in the sheath would suffer.
Molybdenum disulphide or teflon both do as you say but the advantages of the dry-to-film bicycle lubricants are (1) they stay in place, they don't drain away as would engine oil which clearly is intended to stay fluid; (2) drying to a lubricating film they are not messy; (3) dirt and grit doesn't stick to it as they would to a wet lubricant and which, over time, can turn into a grinding paste. This matters at exposed parts, eg. where the trim cable emerges at the tail.
If you don't want black grease but you do want an additive, what about white lithium grease? You can get this from aviation supply or, in smaller quantities, from your local bicycle shop. However the trim control is a 'low use' mechanism so I'd think just about any grease you had to hand would be just dandy.
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Jorgen
Unregistered
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Posted Saturday, April 13, 2013 @ 11:54 AM
All very good advice,
but I realized additives might make it harder to lubricate the whole cable? The geniality of Markku's method is adding some pressure to push the liquids through the whole length of the sheath. Once you've fabricated the bicycle tube setup maybe it's easier just to hook it up once a year and use light oil to lubricate the cable repeatedly.
May the 4's be with you/ Jörgen
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Markku
Unregistered
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Posted Monday, April 15, 2013 @ 05:43 AM
I dismantled the arrangement yesterday, and installed the trim lever. I was happy to notice, that you can rotate the lever with minimum force with a fingertip 
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