Cables / sheath lube

[Lobo]

My daily drive is a split-screen Kombi: dear god, if ever drive-by-wire was needed this is it. The accelerator cable (& clutch) is a 4m long affair, wending it’s way down an aged 6mm ID steel tube, then through a bendy pipe to the jiggling engine. Typical life is 2 years, ie when the 1.5mm stainless cable begins to fray. It’s such an awful dirty job changing it that it gets done habitually versus risking a roadside failure…

So, I want to replace the worn steel / bendy tubes with a continuous nylon one, with no joins, ie accel pedal to carb arm. And here’s the question… should I be lubing the ss cable in any way? And if so, what oil / grease please?

Desperately hoping it can all be kept clean / dry!

[McCabe-Thiele (Ted)]

Do you know anyone who has used a Nylon tube with SS cable is it s known upgrade on VW websites?

I ask as firstly Nylon absorbs small amounts of water when it gets wet causing binding in some applications - I know this as Nylon bearings were used on tin openers in the late 1960's by a local firm - they were great during factory testing but when they went into production after a few washes in the sink even Charles Atlas could not turn the handle.
I would have thought a Pneumatic system might be better as used in the early Hillman Imp accelerator pedal  it was a great throttle action but the materials used in the bellows failed so they were replaced with a cable. Newer generation materials might be more effective in bellows design.


.
http://ckdboats.blogspot.com/2013/02/the-hillman-imp-pneumatic-throttle-foot.html

[Matt_Harrington]

Might be worth contacting venhill.co.uk to see what they say - they could even make a custom one with teflon for you....

[Orcade-Ian]

Lobo,
Surely there's some electronics geek on this forum who might help with a modern solution for your V Dub?
Model aeroplanes use servomotors which should be able to cope with moving the linkage on the carb.  A throttle potentiometer could be used to accurately measure how far the pedal is being pressed.  A model aircraft would then need radio control the marry the two pieces of info but yours can be hard wired, with some kind of electrickery in between.

Ian

[K2-K6]

I've been using silicone oil (sometimes grease depending on application) for cables, particularly smooth and low friction with stainless wire. It doesn't ordinarily degrade or change to "clag" either, so long term consistent performance is reasonably assured.

I feel it's a good shift to move onto a complete sheathed cable end to end in this application, shouldn't be much friction on the predominantly straight run section anyway.

[K2-K6]

Lobo,
Surely there's some electronics geek on this forum who might help with a modern solution for your V Dub?
Model aeroplanes use servomotors which should be able to cope with moving the linkage on the carb.  A throttle potentiometer could be used to accurately measure how far the pedal is being pressed.  A model aircraft would then need radio control the marry the two pieces of info but yours can be hard wired, with some kind of electrickery in between.

Ian

I can see that as most current vehicle use throttle potentiometer often mounted in pedal assembly complete. My son runs a RC nitro car with decent servo for throttle/brake and steering that are quite resilient (36,000rpm, non scale speed near 50mph with alot of vibes and heat) and so hardware potential. 
The car systems from my knowledge usually run into the ecu though with startup checks on position etc to verify neutral operations, how that could be incorporated is likely more difficult for a road vehicle.

It looks to me more like a hydraulic clutch type application, with master and slave, plus long roll of flexible hose. That would be "self zero" effectively and could be designed with non used cable left detached for contingency. The hydraulic advantage over cable being almost nil friction in use and using automotive tested components. 

[Bryanj]

Remeber the first Hillman Imp, they had air hydraulic throttle that left you pumping the pedal to get revs!

[K2-K6]

Remeber the first Hillman Imp, they had air hydraulic throttle that left you pumping the pedal to get revs!

My dad's friend had an imp that had some difficulties  but I was too young to remember the details of what exactly was wrong.

[K2-K6]

OK,  punting around the great wide t'internet and came across this

[ Guests cannot view attachments ]

Apparently used in USA hotrodding applications, seems simple enough concept wise.

[Lobo]

Don’t talk to me about Hillman Imps - I sold my beautiful 400F to raise £s for flying lessons, and with the change bought an Imp. G/f then bought one (and later another) and every w/e thereafter I was grubbing around breakers yards (in the good old days where they pointed you to a corner and you trudged off in the rain with your tools) to retrieve the wanted part. The heater system… aaargh; I used electric gloves to get me over the Pennines on my weekly runs home to get my laundry done / get a good feed.

Wrt electronic throttle system, two issues come to mind. (1) it could have severe legal implications in the event of any accident unless fully declared both to the insurance co - (who would likely then decline) and also Land Transport - who’d demand inspections and all types of brouhaha. It’s a path I don’t want to go down. But more importantly (2), I want to keep the old girl as standard as possible for both simplicity and authenticity. Purely in the interests of safety I’ve fitted front discs, inertia belts and a modern steering rack - but it has stopped there.

Thoughts appreciated- thanks gents; Ted will test soak my tube for a couple of weeks, it is tho’ 4mm ID to carry a 1.5mm cable and so plenty of tolerance.

[Lobo]

… cross posting - is that Hydraulic Nige?

[K2-K6]

… cross posting - is that Hydraulic Nige?

Yes, throttle is hydraulic, seems it's more common in earth moving equipment to use a hydraulic throttle too. That "moon" example appears to be from the custom car scene.

[K2-K6]

slight sideways step in materials https://thepihut.com/products/ptfe-bowden-tube-for-1-75mm-filament seem to be using plain ptfe as bowden cable sleeve.

Remembering some years ago on Tomorrow's world, they had a guy trying to walk in football boots with ptfe studs on a stainless steel surface and without any success as demonstration of almost complete lack of friction.

Trivia, once working for a company completing warranty work at houses, knocked on a door and William Woolard opened it 

Also the Sweeny, John Thaw at another. Not on the same day you'll understand, that would be freaky 

[McCabe-Thiele (Ted)]

Remeber the first Hillman Imp, they had air hydraulic throttle that left you pumping the pedal to get revs!

My dad's friend had an imp that had some difficulties  but I was too young to remember the details of what exactly was wrong.

The Hillman Imp was a great motor close to the end of its production run - I had one as a loan car back in the 1960's - the transaxle seized on the M1 on my way to Bradford.
They overheated if the radiator was not bled properly etc.etc.
My cousin had a 998 Rallye Imp it cheesed me off as it could out perform my tweaked Cooper S - even on corners in the right hands.

Allegedly the air throttles failed due to the supplier cutting corners on the specifications not due to poor design.

[Lobo]

If the (Scottish) Unions hadn’t disrupted the Imp’s production as much as they did, the car could have been better than the mini - so various clips of YouTube suggest. I owe it a lot, especially after hundreds of hours spannering, and hundred more sanding, filling and painting. Happy days.

Thanks Nige for the PTFE outer idea, I’ve been on eBay and securing lengths >2m seems to be the issue, though I have found a 5m run from China (prob infers a ‘no’ that). Q - is this material hard, ie will it resist the odd light knock and NOT deform around light radiuses? I saw a hardness factor of 55, but tbh have no inkling of what that means practically.