Throttle Cable Alignment

[AndyStopford]

Hi, I've noticed that the accelerator pedal action on my Traveller is not as smooth as it might be, and having needed to dis- and reconnect the cable this weekend, investigated this and found that the end of the pedal linkage where the cable is attached does not align with the aluminium casting bolted to the bulkhead through which the cable runs. This is what is causing the graunchiness.

Does anyone know whether this is the usual arrangement, or has my car acquired an incorrect accelerator pedal arm?

These photos were taken with the throttle partly open so that the offending area is visible - the one with the fixing screws removed indicates the sort of position the bale would like to adopt.

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MMThrottle_03.jpg (64.58 KiB) Viewed 7613 times

[King Kenny]

I may be wrong but it looks like a bolt is missing on the left of the cable entry.

[AndyStopford]

Yes, the bolts are removed in one of the photos to show the alignment that the cable naturally assumes

[King Kenny]

Oh yes, I can see it now. The throttle rod looks original as does the holes. If the cable is rubbing then there is no reason you can't realign them. Perhaps file out the hole and redrill for the bolt.

[les]

I can’t see what is causing the misalignment but it should not require alterations to the bulkhead area. Some upward movement of the pedal would help, although I’m not aware of any significant adjustment available there.

[AndyStopford]

Thanks for your replies - evidently not a commonplace situation then.
There's no adjustment in the pedal mountings, so I think I might cut the rod leading from the pedal and insert a small section to make everything line up - certainly a case of measure twice (and test fit twice), weld once, I don't want to end up making it worse the other way if you see what I mean.

[svenedin]

Strange. When my engine bay was repainted I stripped it all out and put it back together again but I didn't paint it myself.

I don't recall having any issues with the alignment. There should be a rubber gasket under the cable guide but I doubt that makes much difference.

Stephen

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[geoberni]

Before jumping in and altering anything, what's the other side look like?
Stephen posted his photo of the engine bay side, here's both sides of my car....

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Check there is nothing in the fitting/guide that is impeding it, a bit of 'crud' or debris.
Is the end fitting of the cable sheath sitting correctly in the guide...

You can see from my photo that the guide is the same size as the hole; so your image of the guide not correctly fitted, and at quite an angle from above, doesn't actually show what your problem is.
We cant see if there's 0mm or 5mm between the cable and the edge of the hole.

If your 2nd, over lit image (we can't see if the bolt is now there), is showing the guide 'in place' then it's too high.
There shouldn't be any aluminium showing.

[stuffedpike20]

Sometimes when an old cable has been replaced in the past, the metal sleeve at the end of the cable is left in the carrier, which interferes with the positioning of the new cable.
This could give graunchiness because the inner cable does not come through the carrier properly.
Check that there is not an old sleeve stuck in the end of the carrier.

[AndyStopford]

This is what it looks like with the guide bolted in place, the first photo with the throttle closed:

MMThrottle_05.JPG (626.08 KiB) Viewed 7048 times

and with the throttle part open:

MMThrottle_04.JPG (745.75 KiB) Viewed 7048 times

Unfortunately, it's very hard to take a photo from an angle that accurately shows the true relationship of the parts, but, the cable is more or less centred in the first, and as the actuating rod swings down, its arc causes the cable to scrape - it seems like the cable eye should be directly in line with the aperture somewhere in the middle of its travel to avoid this.

The overlong bolts suggest someone has had this apart in the relatively recent past for some reason - the cable looks quite new.

I'll check stuffedpike's suggestion at the weekend - that certainly sounds plausible, and if someone had a battle to get the old cable out it might account for the new bolts.

[svenedin]

Fair enough it's difficult to take a picture but from what we can see, the cable doesn't seem to be making contact with the edge of the aperture in the bulkhead. If that is the case, where is this graunching actually coming from? Is the inner cable just not sliding freely within the outer sheath?

Stephen

[stuffedpike20]

This is what it looks like with the guide bolted in place, the first photo with the throttle closed:
MMThrottle_05.JPG

and with the throttle part open:
MMThrottle_04.JPG

Unfortunately, it's very hard to take a photo from an angle that accurately shows the true relationship of the parts, but, the cable is more or less centred in the first, and as the actuating rod swings down, its arc causes the cable to scrape - it seems like the cable eye should be directly in line with the aperture somewhere in the middle of its travel to avoid this.

The overlong bolts suggest someone has had this apart in the relatively recent past for some reason - the cable looks quite new.

I'll check stuffedpike's suggestion at the weekend - that certainly sounds plausible, and if someone had a battle to get the old cable out it might account for the new bolts.

If the end of an old cable has been left in, the new cable end will not seat properly.
An end left in can be removed by screwing a self tapping screw into it and pulling on the screw with pliers, or by drifting it out from inside the car using a suitable diameter drift. Be careful because the metal of the guide will be brittle.

[geoberni]

This is mine at fully depressed Throttle.
It doesn't really look any different to yours; I think you have a problem up inside the fitting.
As I and stuffedpike said, something in that fitting isn't right.

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When I got my car almost 9 years ago.. ... I discovered that at a major rebuild around 1999/2000, someone had got carried away with welding up all the holes they presumably thought they didn't need.
Including the ones for securing the guard plate over the moving throttle bar...
Photo from 2019, just before I fitted one.

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[stuffedpike20]

I once had a moggy with a beautiful silvery chrome handbrake lever. An MMOC young member pointed out to me that it would have origionally been from a mini! (God bless those young members. They are the future of the club, and so knowledgeable about the cars.)

When I see something wrong about a moggy now, I think 'could these parts actually be from a mini, or another type of car?'
Is a mini accelerator pedal similar to a moggy, but slightly shorter?

[AndyStopford]

@stuffedpike: Absolutely, many a decades old vehicle must have become a parts-bin special to some extent.
There's also the possibility that replacement parts may not be made to the same tolerances as the original...

so...

I took the cable and guide out again and examined them closely.
I found that the first section of the guide has a bore of 6.45mm, suggesting the possibility that it is intended to be a loose fit on a 1/4" (6.35mm) spigot.
There is then a restricted section 4.8mm diameter, see below:

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The end of the cable sheath has a ferrule with a section of 5.5mm diameter for 10.7mm, then a crimped part of 6.35mm diameter.
The 5.5mm section can only enter the first part of the guide in which it is quite a loose fit. This means the inner, moving cable passes through the restricted
4.8mm diameter of the guide unsheathed and can rub on it.

It seemed to me that if the first section of the ferrule was reduced in diameter, this arrangement would make much more sense:

ThrottleCable.jpg (86.28 KiB) Viewed 6893 times

Since I had a spare cable (which was dimensionally similar, though not identical) I decided to try this out.
The only way to mount this in the lathe was to grip the crimped part in a collet, with the cable sheath passing through the lathe spindle and emerging to
thrash around at the other end of the headstock - not an ideal arrangement, so I ran it pretty slow and took very light cuts. The cable behaved itself
surprisingly well, and I reduced the ferrule end to 4.7mm (4.76mm = 3/16" which seems likely as the design dimension).

This fitted nicely, as per the drawing above, and when tried in the car the action was much improved, with the binding and grating gone.
Note - this doesn't mean that these new manufacture cables will always be problematical - I suspect that there will be a range of dimensions and some may work fine, but if anyone encounters one that seems to bind, this may be worth checking.

[geoberni]

All very informative, but personally speaking, IMHO, you're engineering a high tolerance solution to a problem that isn't there and actually not finding the real issue.

This is not something engineered to a high tolerance, such a carburettor jet orifice, it's simply a bit of Boden Cable with no greater tolerance than what you might find on a basic bicycle brake lever of the late 1940s, because that is the era we're speaking of.
Here's a couple of photos taken this morning, including one with a basic endoscopic camera that plugs into my phone.
I've already posted an image on Wednesday of the Ferrule sitting in the casting.
So here's the Ferrule pulled out and the inside view of the cable proceeding into the car.
Plenty of room for the cable and the thinner diameter section on the ferrule, where yours measured 0.55mm, mine measured 0.52mm, and doesn't disappear to a high tolerance fit in the casting.
My car's throttle operates perfectly fine.
.

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.
I know you said the problem has now gone, but it all seems very odd to me.
You've effectively replaced the cable, therefore disturbed the Carburettor end as well as anything else.
How do you know it hasn't cleared up because of that, irrespective of your machining?
Conclusive proof would be to refit the original cable and confirm the fault reappears.

But you've got it working which is the main thing....

[AndyStopford]

But it is the original cable - I preferred to possibly ruin that, rather than a brand new one.

[geoberni]

But it is the original cable - I preferred to possibly ruin that, rather than a brand new one.

OK, I read your commentary as that you had machined the spare one, but it doesn't alter the fact that you had completely removed it and refitted it.

It works for you, and I understand your viewpoint you're the person fiddling with it, but personally I don't see why your standard installation was giving a problem. There's invariably a simple solution to such matters.
I just don't see a justification for you to machine the parts to a close (0.1mm) tolerance, to improve the situation.
Ce La Vie.

[les]

I’ll never look at those cable ferrules in the same light again ! There was me thinking it was a simple component.

[panky]

Heaven forbid someone has shown a bit of initiative and skill to sort out a problem on his own car in his own way.
Nicely done.