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clutch cable keeps breaking - other alternatives


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  • 1 year later...

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Thread revival again!

OK - I need to make one of these while my pedal box is out.  I started by making the largest pulley that would fit in the space to reduce the radius the cable has to travel through.  When I fitted it and looked at the cable in relation to the pedal pivot the cable was rubbing against it - so back to square one!

The arrangement earlier in this thread looks like it is made from a modified bicycle freewheel sprocket, but all the ones I have looked at are too wide (thick) to fit in the pedal box "slot" (13mm), and I'd rather not start modifying that.  Any idea where the cycle parts came from?

Thanks very much

Pete

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Go hydralic and put a concentric in it.  this link to the Excel forum is for an Excel /toyota grearbox but it wouldnt be that difficult to make to fit your boxes.  the only thing to watch is that if you use a flat faced concentric you need to use a pressure plate with curved end tips,or vice versa.  this concentric is a SAAB one but as long as it fits over the gearbox nose any will fit.

 

Bash

http://www.lotusexcel.net/phpbb/viewtopic.php?f=3&t=11207

 

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5 hours ago, EXCEL V8 said:

The arrangement earlier in this thread looks like it is made from a modified bicycle freewheel sprocket, but all the ones I have looked at are too wide (thick) to fit in the pedal box "slot" (13mm), and I'd rather not start modifying that.  Any idea where the cycle parts came from?

Thanks very much

Pete

Looks like a bicycle chain running over a jockey wheel. this is a part of the rear derailleur gear of a bicycle,  much narrower than a freewheel and available inexpensively  from your local bicycle shop.

We throw them in the scrap all the time when the derailleur body is twisted.

The chain to cable  connectors I'm not so sure about.

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Thanks guys.  Hi Bash!  Defo staying with cable operation on this one - you know I don't like to re-engineer everything!!  Hi tom - I've looked at jockey wheels - they all look a bit too insubstantial since I'll be running an up-rated clutch cover, and I'm not sure the one in the picture is a jockey wheel - it looks like it's all steel with 13 teeth.  The chain connectors are custom-made I'm sure - that's not a problem. Rob - you absolutely right - a scaled up version of the Sturmey Archer hub-gear change is exactly what I need!  So - my current plan is to weld a Sturmey Archer sprocket to a small steel hub with a roller bearing at it's centre.  I'll order some bits today.

Pete

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After my second cup of coffee of the day... I’ve had another thought....

 

sturmey archer chains are tiny, full sized bike chains would be a better option 

you could cut up a chain whip (remember to search chain whip cycle tools... other wise you might get some in unintended search results)

try chain reaction cycles 

 

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1 hour ago, Straker said:

sturmey archer chains are tiny, full sized bike chains would be a better option 

 

I will be using proper cycle chain - the Sturmey archer sprockets take 1/2" x 1/8" standard sized chains

1 hour ago, Straker said:

Some SRAM deralliers have 13 T jockey wheels and there are aluminium ones available from several companies that run on cartridge bearings 

I looked at those as well.  Still need to do more research on the width of the units and the pivot bolt sizes (8mm holes in pedal box).  I noticed some of the SRAM-type have large centre holes for mounting - presumably on some sort of bushing?

Pete

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Pete there's a 16 tooth jockey wheel in the post to get you started.

There are bolt- on cable ends available to connect the chain to the cable,  if they are strong enough - I'm thinking just run through the last chain link?

Tom

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Pete,

the large bore on some SRAM jockey wheels is to allow for a large busing to provide float in to deal with changes I alignment.

another option to deal with connecting with the chain could be to use a clevis fork to connect to the outside of the chain, or  a clevis piece to the inside the end of the chain.

the easiest way to join something to the chain would be to use a power link (tool free chain link)

springfix linkages have lots of different Clevis joint sizes listed  

 

R

 

 

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Have a look a this site but you are going to get a much stronger sprocket / chain by using motorcycle gearbox sprockets.

Bash

https://uk.rs-online.com/web/c/pneumatics-hydraulics-power-transmission/power-transmission-sprockets/sprockets/

 

Ps, or you could use a duplex reynolds chain and the small bottom sprocket from a Rover V8 duplex setup.

 

 

Edited by hedgehogjuggler
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I spent more time looking at this again today.  If the jockey wheel idea comes to nothing (only the strength of these would stop them being useable) the thing stopping an easy fix is the bit in the pedal box where the pulley mounts - it's only 13mm across, preventing the use of all but cycle chains.  I might just cut it out completely and make a plate with a "stub axle" on it that bolts to the side of the pedal box in the same position.  I could then use any number of sprockets with a wider tooth profile to allow ISO-sized chains to be used.  This would allow easier connection to the cable/pedal as well.

I'll wait until I get the jockey wheel from Tom before I go any further though.

Thanks for all the ideas guys!

Pete

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Don.Hasi from Germany has been running a chain and chainwheel set-up on his Eclat for 20 years (see page 1 of this topic) so whatever he did works well.  Why not ask him for details?

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S4 Elan, Elan +2S, Federal-spec, World Championship Edition S2 Esprit #42, S1 Elise, Excel SE

 

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Spent a couple of hours in the shed this evening.  Below are some photos of commercial derailleur jockey wheels and one I made myself.  The original pulley is there for comparison.

The first is a jockey wheel kindly supplied by Tom - thanks Tom!  It is made from a kind of nylon-filled thermo-plastic.  It's fairly strong but has no bearing - the outer sprocket runs on a small steel bush.

 

RIMG0452.thumb.JPG.6e940827b449aea2f243a6ee6ac3f69e.JPG

 

The next is an anodised aluminium jockey wheel off fleabay.  It's just too flimsy to last long given that I'll be running an up-rated clutch cover, although it appears to run on a small bearing.

 

RIMG0454.thumb.JPG.9fd0701083aaa04fe173102495a8f939.JPG

 

The next shows a Sturmey Archer hardened steel sprocket (14T)

 

RIMG0455.thumb.JPG.eb063212ae6c78b7fba0a53ef1e38535.JPG

 

The next shows my home-made "jockey wheel"

 

RIMG0456.thumb.JPG.483d7342cc9bfad0fe9367cf69579d77.JPG

 

The hardened steel sprocket (13T) is a press fit onto the steel hub that I machined (could be welded as well).  The centre bearing (also a press fit) is a "max fill" sealed deep groove ball bearing with an extended inner race that happens to match the 13mm gap in the pedal box bracket and takes an 8mm clevis - also the same as the pedal box!  This bearing took some finding - very few have the dimensions that I wanted.  The max fill spec increases the load capacity by ~ 1/3rd.  This is what I'm going to use in my chain conversion.  Next is to buy a chain to mess about with and some wire rope terminations for the clutch cable.  Watch this space!!

Pete

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I replaced my nylon pulley with an aluminium one that had a ball race bearing.

I got it at a boat chandlers, used for wire control cables on a yacht.

I found that the nylon one was squashing and then binding when under pressure from the cable.

Nice job with your conversion Pete!

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I found a few "fixed gear" sprockets might do the job, - mostly 20 tooth to fit onto a BSA 1.37" x 24 tpi rear hub - a bicycle non- drive side bottom bracket cup is the same thread, so I could chop one down and press in a suitable machine bearingIMG_20191216_183613.jpg.6b443653cd85e66a7d28703d01abd43f.jpg

I've been wondering about the best  cable to chain connector - what's a rough guess at the pull force involved - should be newtons I think but let's say in kilos?

I mean that attachment point needs to be more reliable than the cable running over the roller. - i assume the chain will run from the pedal lever round the sprocket, then attach to the cable  - using a pigtail hook perhaps?20191216_190055.jpg.597494b3409066d5358f64463d138260.jpg

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20 teeth may be too many.  The effective diameter of the original pulley is about 50mm.  When I increased this with a larger aluminium pulley the cable ended up rubbing on the pedal pivot just as it enters the pedal box on the bulkhead.  The 13 tooth one I made has an effective diameter of about 53mm.  I'm going to order a couple of swage-on cable ends to play with.  One other problem might be the thickness of the original cable - it measures less than the "normal" 3mm wire rope diameter, so I may end up making my own termination or trying to fit some 3mm cable into the original outer.

Pete

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Using spacers from 10mm thick upwards

its hard to be definitive as the cogs vary in thickness depending on manufacturer 

I can see why the aluminium jockey wheel was so flimsy, I think it’s worth considering alternatives as  there are more robust ones made by ‘Hope’ in the uk they’ve been making bike bits for almost 30yrs and are run by ex BAE systems guys.

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