The BSA A7-A10 Forum

Technical => Clutch, Primary, Gearbox => Topic started by: RichardL on 06.09. 2015 21:30

Title: Clutch Cable Length
Post by: RichardL on 06.09. 2015 21:30
Trying to reckon the best way to calculate clutch cable length and looking for comments on my ideas. This stuff will be common knowledge for many here, but not me. I was using the original '55 cable (out of service from '79-'03) until it frayed a month ago and I grabbed the cable off of my '57 barn find. That cable was fine for a couple of rides but got much too sticky, and oiling didn't help. I was unable to make a working cable from the scrap and now face prime riding days without a working bike.

I will have a typical adjuster at the lever and the threaded tube adjuster at the gearbox. My thinking is that I should position both of these adjusters in the center of their travel and measure housing length between them. Then, I figure add the minimum exposed cable length to reach the unengaged clutch operating lever and the un-pulled handlebar lever. Is this close to the way it's done? Should the adjusters be positioned for the maximum housing length instead (or vice versa)?

Thanks, guys. It seems no matter how long I play this game there is some rule I am yet to encounter.

Richard L.
Title: Re: Clutch Cable Length
Post by: bsa-bill on 06.09. 2015 21:45
I think you should allow for inner cable stretch Richard, (doubt it will shrink) so I'd set the adjusters to allow for that at a future date
Title: Re: Clutch Cable Length
Post by: beezermacc on 06.09. 2015 23:22
When making cables I usually screw all the adjusters fully in, then out maybe one turn, then make the cable fit. I then usually find I need to screw the adjusters out a couple of turns after fitting the cable.
Title: Re: Clutch Cable Length
Post by: duTch on 07.09. 2015 02:39

 I'll second both the above
Title: Re: Clutch Cable Length
Post by: RichardL on 07.09. 2015 05:09
Have to admit, never thought about the workings of my cables as much as I am right now. Trying to get my head around where clutch cable adjustment comes from or if there even is such a thing. The housing must remain trapped between the adjusters and the needed length of exposed cable is fixed for a given clutch activating arm position. If you unthread one or both adjusters you're just bending the housing with the cable inside. Maybe that pulls marginally on the cable, but doesn't seem a great way to plan for adjustment. This leaves me with the feeling that the only true adjusment for the clutch may be the screw behind the oval cover. I think I hope I'm missing something obvious.

Richard L.
Title: Re: Clutch Cable Length
Post by: cyclobutch on 07.09. 2015 07:28
Well there are only two critical dimensions - one being that the overall length reaches well enough without going around the houses three times, and the other is the differences between the inner and outers. The adjusters are only there to maybe allow the cable to be fitted, and then just to take up minor differences.

Best bet is to note that inner to outer difference when you have a good fitting cable, then make up to that next time out. Not much help if you've already substantially stretched or busted all of yours.

Adjustment at the arms and levers should really be used to allow them maximum advantage I would have thought.

Surely someone here can give a measurement for this that should be suitably average? I'm not even remotely near my bike right now.
Title: Re: Clutch Cable Length
Post by: sparx on 07.09. 2015 07:30
I think the "obvious" that you're missing is that the outer cable doesn't "bend" to any extent when it's compressed. Think of it as a solid tube that is flexible.
 
Title: Re: Clutch Cable Length
Post by: RichardL on 07.09. 2015 08:11
I think the "obvious" that you're missing is that the outer cable doesn't "bend" to any extent when it's compressed. Think of it as a solid tube that is flexible.
 

Agreed, the adjusters can put the housing under greater (or lesser) compression. So, it seems, if centered when measuring for the housing, they can also expose more or less cable at one end or the other by turning one in and one out. It also seems there is no compensating in the adjusters for a cable that is overall too long or too short (as I believe was Butch's point).

Richard L.
Title: Re: Clutch Cable Length
Post by: bsa-bill on 07.09. 2015 08:34
Quote
It also seems there is no compensating in the adjusters for a cable that is overall too long or too short

The critical measurement is not the overall length or lack of (provided it will reach the two points of anchorage) but the difference between the inner and the outer, this is what the adjusters adjust
Title: Re: Clutch Cable Length
Post by: muskrat on 07.09. 2015 10:29
G'day Richard.
Just measured mine. The gearbox adjuster is part of the cable, the hand lever adjuster stays in the perch. So with the inner removed from the gearbox lever and the hand lever & perch and pulled till the nipple is against the gearbox adjuster there is 2 and 3/8" of inner to the inside of the hand lever nipple. Pics explain it better.
When it's all together the adjusters are at their smallest giving full length adjustment.
Cheers
Thought I'd better add. The gearbox adjuster is 1 and 3/4" so that makes the inner 4 and 1/8" longer than the outer not counting the nipples. Clear as mud!
Title: Re: Clutch Cable Length
Post by: duTch on 07.09. 2015 11:19

 Richard, you may be over complicating it....I just referred to my 'notes' (which I had to edit to understand), but with adjusters top and bottom came up with a difference of ~108mm between the outer and inner, which is fairly close to Muskies 4+1/8" ...If you're making your own, do the top nipple and back off all adjusters, as per previous advice, and locate the bottom one where it needs to be, and you can't go wrong...Best to have at least one, preferably both nipples with swivel capabilities
Title: Re: Clutch Cable Length
Post by: RichardL on 07.09. 2015 14:48
Quote
It also seems there is no compensating in the adjusters for a cable that is overall too long or too short

The critical measurement is not the overall length or lack of (provided it will reach the two points of anchorage) but the difference between the inner and the outer, this is what the adjusters adjust

Bill, It seems to me that the outer ("housing") must remain trapped between the adjusters, so I can't see how they they can affect the difference between the inner and outer while doing that job.

Muskrat, I get your photos and they are helpful. Dutch could be right about overcomplicating (it is one of my faults, which are many) but I have more questions. But first, let's call it 2-9/16" so we're measuring to the center of the pull hole. The question is, is 2-9/16" at the lever the exact length between the inside of the adjuster to the center of the pull hole (lever not pulled, of course)? You say "adjusters are at their smallest" but this confuses me. I'd like to have the adjuster at the lever as far into the perch as possible for stability. So, this raises the question: assuming your cable inner and outer fit perfectly, what are the adjuster positions? are they all the way in or about halfway into the gearbox thread and lever? No need to be exact because another thing at play here is if we have the exact same perches? I can already see we don't have the same lower adjusters (mine will have the thumbwheel).

Dutch, Thanks for your contribution. Please explain "back off all adjusters." Do you mean before or after deciding on the housing length?

OK, I have well-tortured this topic and maybe all my friends here. Thanks for any additional info or opinions you have time or interest in offering.

Richard L.
Title: Re: Clutch Cable Length
Post by: RichardL on 07.09. 2015 14:57
When making cables I usually screw all the adjusters fully in, then out maybe one turn, then make the cable fit. I then usually find I need to screw the adjusters out a couple of turns after fitting the cable.

I should have mentioned earlier that this seems quite logical to me for fitting the housing.

Richard L.
Title: Re: Clutch Cable Length
Post by: RichardL on 07.09. 2015 16:28
All in unison now, "Group groan."

Looking at the photo, you can see the distance from the rear of the adjuster to the center of the pull hole. Taking into account the depth inside the adjuster, if I let 2-9/16" be exposed here, the adjuster will be out of the perch. If 2-9/16" is the total exposed (with the bottom adjuster on the cable), it appears the cable will come up about 3/8" short.

Obviously, I'm determined to beat this to death. Feel free to grab a bludgeon and join in if you want, but if I've proven myself too thick to absorb advice, you are free to sit in the stands and just point your thumbs up or down while I await the lions.

Richard L.

Edit: The photo is upside down, but so what.
Title: Re: Clutch Cable Length
Post by: bsa-bill on 07.09. 2015 17:48
Quote
Bill, It seems to me that the outer ("housing") must remain trapped between the adjusters, so I can't see how they they can affect the difference between the inner and outer while doing that job.

 because screwing the adjusters in or out alters the length of the outer in comparison to the inner, you have the length of the adjusters to add to or subtract from the original length of the outer.
How did you guys get to the moon  *smile* *smile* *smile*
Title: Re: Clutch Cable Length
Post by: RichardL on 07.09. 2015 19:08
Quote
Bill, It seems to me that the outer ("housing") must remain trapped between the adjusters, so I can't see how they they can affect the difference between the inner and outer while doing that job.

 because screwing the adjusters in or out alters the length of the outer in comparison to the inner, you have the length of the adjusters to add to or subtract from the original length of the outer.
How did you guys get to the moon  *smile* *smile* *smile*

We wore Swiss watches. But seriously, you can't change the lengtth of the outer with respect to the inner by using the adjusters. The outer isn't stretchy springy. What I think  happens is that you can retract and extend the inner with respect to its attachment point because, when the opposite end is anchored,  the outer and inner move together while changing the arc of the slack with the adjuster.

If this is right, I'll still but your beer (within reason!)*when we ultimately get together.

Richard L.



Richard L.
Title: Re: Clutch Cable Length
Post by: bsa-bill on 07.09. 2015 19:36
Quote
you can't change the lengtth of the outer with respect to the inner by using the adjusters.

if you count the adjusters as part of the outer then of course you can, every time you turn an adjuster a full turn you alter the outer by the length of one thread on the adjuster.
Just to demonstrate and confuse matters even more
If t = one thread ( say 1/16th of an inch) then in the above quote you altered the length of length to lengtth, 1/16th longer than it was before  *smile* *smile* *smile*
Title: Re: Clutch Cable Length
Post by: RichardL on 07.09. 2015 19:55
Uhh, let's assume the ends of the inner are not connected. Once the backsides of the adjusters are both in contact with the outer, all you can control with the adjusters is how much gap exists between the ends of the outer and the basksides of the adjusters OR the general position of the outer (that is, either slightly closer to the lever or slightly closer to the gearbox, but still snug between the adjusters).

Is Budweiser expensive in England? How about Foster's?

Richard L.
Title: Re: Clutch Cable Length
Post by: duTch on 07.09. 2015 20:27

  *bash*
Quote
Feel free to grab a bludgeon and join in if you want,

 
Quote
But seriously, you can't change the lengtth of the outer with respect to the inner by using the adjusters. The outer isn't stretchy springy........ *conf2*.....
Yes you can, as Bill said which is much the same as;
Quote
What I think  happens is that you can retract and extend the inner with respect to its attachment point because, when the opposite end is anchored,.....
(But I have to suggest that the bottom adjuster is BSC/26tpi which will equal every turn to be 1/26" not 1/16" *shh*)
 
Quote
the outer and inner move together while changing the arc of the slack with the adjuster.
   *????* *????*
 Anyway- apart from a few overall measurements for later reference, you're best to hide all the measuring devices and simply make it to fit; fairly much as Beezermacc said

 1> select a overall outer cable length that is not too tight bends, nor likely to bind/stretch when turning handlebar.
 2> screw adjusters '~fully in' (giving consideration to lever/arm-adjuster conflict- **see photo with arrows and circles- thanks muskie) **
 3> fit a nipple to one end (which end doesn't matter- top first may enable easier bottom fitment? ) make inner cable to suit with arms and levers in 'riding position/transit mode'
 4> Ride bike

 ** this is important, top and bottom- otherwise lever will be restricted in its travel
Title: Re: Clutch Cable Length
Post by: RichardL on 07.09. 2015 20:55
 *problem* *fight* *pull hair out* I'll float it again. The physical length of the outer housing does not change with movement of the adjusters. Nevertheless still trying to avoid  ::hh::

That said, Dutch, your method sounds perfect, except I was trying to figure out fairly accurate numbers to give to a shop to fabicate the cable for me.

Richard L.
Title: Re: Clutch Cable Length
Post by: bsa-bill on 07.09. 2015 21:04
Quote
(But I have to suggest that the bottom adjuster is BSC/26tpi which will equal every turn to be 1/26" not 1/16" *shh*)

yes your right of course the 16th was just for example purposes  *smiley4*

If we ever meet Richard I'll buy the drinks, I just admire your persistence  *smile*
Title: Re: Clutch Cable Length
Post by: morris on 07.09. 2015 21:17
For a clutch cable I usually have a look on a reputable dealers' website, select the one I want, sit back, relax and wait for the postman...
Resulted in two cables of perfect length. One for the plunger and one for the SA.
*beer*
Title: Re: Clutch Cable Length
Post by: RichardL on 07.09. 2015 22:02
That may be easier in the UK (but maybe not Belgium) than here in the US, but it's a holiday weekend and I've been unable to phone anyone here (and just realized I could have phoned SRM today for their opinion). I'm still concerned that the stock part number may be the wrong length inner consider the original lever did not have an adjuster, but today's aftermarket versions do. Also, I didn't want to wait for Uk post.

Richard L.
Title: Re: Clutch Cable Length
Post by: duTch on 07.09. 2015 22:23

 I knew that Bill *smile*....but in case someone reads it in the future and takes it as 'set in stone fact' *contract* *smile*

 The reason I suggest ditching the measuring devices is because each bike is likely to be slightly different, depending on levers and stuff...
  I've attached the photo of my 'notes'- don't try and analyse it...*conf*... this refers to the cable that like Morris, I bought for my Plunger from a place (Trojan Classic in Sydney), thought the outer was too long so cut a bit off, only to find it was ok anyway- I'd done something dumb but can't recall what.
  It's shorter than the previous one I bodged, but maybe a bit too short overall, which reminds me I need to swap them over (note to self)

 ..and don't forget
Quote
Best to have at least one, preferably both nipples with swivel capabilities
 
Title: Re: Clutch Cable Length
Post by: cyclobutch on 08.09. 2015 06:03
But going back to an earlier point – yes you would expect the inner to stretch over time. That would introduce more slack into the system e.g. clutch lever would come back further towards the bars. You adjust this by winding an adjuster out a little; thus effectively introducing that stretch amount into the outer. Normal operations are restored. That may help, but I have another observation (which won’t) …

I’ve also had cause to mess around with bicycles over the years. On these a cable is used to operate the gear shift at the rear derailleur. A couple of my gear cassettes back there are 10 speed, so the adjustment is quite critical  to ensure good crisp indexed shifting. And over time they do move out and need a tweak. BUT – it is always as if the inner has shrunk. I have to move the adjuster to effectively reduce the outer length. How can this be? The inner surely hasn’t really shrunk, but similarly the outer can’t have grown. Wear in the shift mechanism?

Beyond which, I think Richard should consider a hydraulic conversion.
Title: Re: Clutch Cable Length
Post by: morris on 08.09. 2015 06:17
Beyond which, I think Richard should consider a hydraulic conversion.

Now that would be the day...! *smile*
Title: Re: Clutch Cable Length
Post by: bsa-bill on 08.09. 2015 09:36
Quote
Beyond which, I think Richard should consider a hydraulic conversion.

but then there is the length of the pipe to consider  *whistle*

Quote
I knew that Bill *smile*....but in case someone reads it in the future and takes it as 'set in stone fact'
of course , sorry was a bit befuddled at the time

Quote
preferably both nipples with swivel capabilities
now we're talking (but not necessarily BSA) *smile*
Title: Re: Clutch Cable Length
Post by: RichardL on 08.09. 2015 11:26
You adjust this by winding an adjuster out a little; thus effectively introducing that stretch amount into the outer. Normal operations are restored.

And over time they do move out and need a tweak. BUT – it is always as if the inner has shrunk. I have to move the adjuster to effectively reduce the outer length. How can this be? The inner surely hasn’t really shrunk, but similarly the outer can’t have grown. Wear in the shift mechanism?

Per my previous, I am still thinking that taking up such excess exposed inner (while the other end is anchored) is a matter of pushing the outer away from the lever and into a different radius. The inner would then be along for the ride.

As for derailleurs, you made me go to Google to review their operation. I have a vintage Raleigh Competition, that I bought in ''73, the same year I bought my A10. I am really shooting in the dark here (and way off of A10s) but wouldn't a shorter cable tend to pull you toward lower gears? Taking Relativity into account, this seems the same affect as a weak spring attempting (and unable) to return the derailleur to the highest gear.

As for hydraulics, never before the sun crosses the yard arm.

Richard L.

Title: Re: Clutch Cable Length
Post by: Greybeard on 09.09. 2015 13:47
Richard,
I have not read all of the above posts but I started to write this a while ago so thought I'd post it anyway.

I've made up bicycle cables but not motorbike ones. This is how I would make a clutch cable. First of all just plan and fit the outer cable, making sure that it has a nice, easy run, taking into account full lock steering movement.
For the inner, attach the top nipple and put it into the handlebar lever. Grease the cable and feed it into the outer, not forgetting the adjuster at the gearbox. The adjuster should be screwed well, (but not fully*) into the gearbox abutment to later allow for the outer to be lengthened, which has the same effect as shortening the inner if/when it gets stretched. Make sure the inner cable is pulled properly tight and mark where the gearbox nipple needs to go. Cut the cable; thoroughly clean the grease from the cable strands and the nipple. Slide the nipple on and splay the ends into the nipple countersink then solder or braze the nipple into place. Adjust if necessary, (*by screwing adjuster into the abutment) to give a small, (1/8") slack of movement.
Title: Re: Clutch Cable Length
Post by: RichardL on 09.09. 2015 19:56
Good method, as far as I can tell.

Richard L.