One throttle cable (2017)

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baz said:
madass140 said:
thanks for the input, The sole idea of this conversion is to eliminate out of sync cables. Now to make it easier to adjust
needle position without removing the top of the carb... I'll have to put my thinking cap on...
Click to expand...
No not without removing the carb top, although that would be brilliant!, Not sure about a t150 Trident set up that looks like yours, but a t160 really is a pain to change a needle position or slide cutaway,also the seals on the carb tops can be fiddly ,also wear in the bushes just a few thou throws the carbs out of balance, having said all that I'd much rather have a gantry than a cable splitter so mark me down for one , cheers
Click to expand...

So, how often does the Norton (British motorcycle) owner change slides or needle positions?? Once, possibly twice, during the run of the tuning? Yes it is a PITA, but I'd rather do that than shim the old Isolastics...
 
yes RoadScholar I agree, I think those concerns are coming mainly from the racer set and with good reason. I had considered having the option but If I was to make a good production run then I would make them all the same "racer style" .
Don
 
Very nice project, Don! And elegant too.

A couple concerns. The top plate needs very accurate machining to seal the carb tops. I guess you cnc-machined your sample.
Also, are carbs manufactured accurately enough to warrant the top plate will fit any carb pair? A slight twist between flange and body, and the plate will no longer fit.

Wouldn't it be better to leave the Amal carb top covers in place and make an actuator fitted on a forked sheet metal structure of 2mm thickness clamped between the carb and inlet manifolds, sort of T160 style? It would be cheaper to manufacture and would facilitate a cable restraint as well, rather than your fatigue-prone bracket. Re. concerns of stiffness, the structure could be additionally supported at the balancer tubes which are threaded in your application. It's all a bit tight but I believe it could work.

Rgds.

Knut Sonsteby
 
Hi Don, I could do with that system on my race bike as I am running Mk1 Premiers and irt would fit my bike very well.
Once you go intp production, I am up for a set , will you make 2 x options, one system to accommodate chokes and one without?
I dont use chokes on mine.
Also while I have your attention, I need a new tank cap rubber seal for that gas tank you made for me, any idea the part number?
Regards Mike
 
https://photos.smugmug.com/One-cable/i- ... 003-XL.jpg

Geez Knut you're on the ball, I was going to post some pics later today with it all together but here is the latest.
Regarding your other concerns
I tried fitting the plate to a 2 unmatched carbs from many years apart and found one carb was taller than the other.
I since tried it on a pair of Amal Premiers and a pair of Wassell (Premiers) and both were the same height.
This would be the scenario when fitting the plate " slightly loosen the 4 carb allen screw mounting bolts, fit the top plate with all 4 screws tightened
then tighten the 4 4 carb mounting allen screws. this seems to work fine.
Todays project is looking at alternatives for cable restraint,
thanks for the input
Don your bits went out yesterday
 
https://donaldpender.smugmug.com/One-cable/i-JpNBp5L
https://donaldpender.smugmug.com/One-cable/i-thTZB2b
https://donaldpender.smugmug.com/One-cable/i-vSrwdqw
It will be something like this, looks like the cable riser restraint will be TIG welded on.
It will come with 4 longer carb top screws and probably a new set of slide springs
When ? 2 months or so I reckon
How much ? havent got a clue but it will be affordable and a good investment.
Remember you will be riding down the road knowing that them carbs are always in synch.
 
Hi Don,do you have seals fitted to the carb tops? And what sort of bearing/bush is used on the pivot? Cheers
 
not shown but there will be seals (guides) for the lift cables. the main shaft pivots on the 5/16" heim joints (rod ends) I was going to fit very small bearings
in the other end for the trunions but cancelled that, a drop of oil once in a blue moon on them should suffice.
 
madass140 said:
https://donaldpender.smugmug.com/One-cable/i-JpNBp5L
https://donaldpender.smugmug.com/One-cable/i-thTZB2b
https://donaldpender.smugmug.com/One-cable/i-vSrwdqw
It will be something like this, looks like the cable riser restraint will be TIG welded on.
Click to expand...

Don, TIG welding is an improvement, but the right angle cable riser restraint is an extreme stress riser design. Ideally the transition should be evenly curved and the joint should be on the straight section. If you can't fabricate it accordingly, I strongly recommend welding a small triangular stiffener centrally located at the transition. It´s still not ideal.

A better design would be to make the riser restraint out of a bar rod shaped like a polygon and weld it horizontally on top of the plate by a circumferential fillet weld twice the length of the riser restraint width. This ensures low stresses in weld seam as well as in the riser restraint. I would weld before machining the plate underside, to ensure perfect flatness.

Best regards,

Knut Sonsteby
 
yes I had thought about using rod . Its only got to take the load of 2 light springs, I'm not at all concerned about the strength of the bracket or its weld.
 
Don, the potential failure is due to fatigue, not static load. Cantilever design means a low eigenfrequency. That's why the T160 design is a heavily ribbed non-welded design which meakes it much stiffer, increases natural frequency and ensures no residual stress. Please remember that welding aluminum significantly reduces yield stress and produces high residual stresses, unless post-weld heat treatment is applied.

Based on an assumed cross section of 5x30mm, a length of 100mm and aluminum as material,
the first natural frequencies are f0=411 Hz and f1=2567 Hz. f0 may be excited by the firing interval of each cylinder at idle and is probably the most dangerous excitation due to high amplitude.
f1 may be excited by the crankshaft at normal running revs or by each firing cylinder at higher revs. It's dangerous due to being a sustained load.

A bar rod could be welded top/bottom of the plate by providing an oblique drilling. Assuming a Ø10mm rod and identical data otherwise, the first natural frequencies are f0=727 Hz and f1=4546 Hz. This ensures far less likelihood of excitation, IMHO.

-Knut
 
". It's dangerous due to being a sustained load."
Ok lets put this "load" in to perspective. Put a slide spring between finger and thumb and compress it 1" (25.4mm)
Now x 2 , would you really consider that sustained load enough to cause the weld to fracture??
Keep in mind I intend supplying lighter springs.
 
madass140 said:
1/4" x 3/4" over 2-1/2"
Click to expand...

The data you provide yields first natural frequencies of f0=1261 Hz and f1=7880 Hz. f0 is out of normal idling rev excitation which is assuring. It may still be excited by the firing interval of each cylinder at normal running revs. The excitation amplitude is probably fairly low. f1 is not a problem.
Still, I would consider PWHT.

I should add that partial weight of cable, ferrule and adjuster hasn't been accounted for, nor has damping effect of the cable. These factors could bring f0 down to 900-950 Hz, which makes the riser restraint susceptible to excitation by idle revs. It's hard to assess these effects without further data.

-Knut
 
madass140 said:
". It's dangerous due to being a sustained load."
Ok lets put this "load" in to perspective. Put a slide spring between finger and thumb and compress it 1" (25.4mm)
Now x 2 , would you really consider that sustained load enough to cause the weld to fracture??
Keep in mind I intend supplying lighter springs.
Click to expand...

Don, the potential failure is due to self-weight of the riser restraint and the excitation produced bye the engine. I am dismissing static load by springs as cause of failure.

Cheers,
Knut
 
Hi maddass140 / Don,
I would definitely be interested in this product if you decide to go forward, however could I make a couple of observations / suggestions ( which I'm sure you have already thought of, and I realize this is a prototype )

1) Given that the carb tops will be 3 - 5 mm higher than standard (a guess from the pics), is there any danger that at WOT the tip of the needles will pass out the top of the main jet and jam them wide open ? i.e. needle moved to the bottom groove etc. Like I say i'm sure you've thought of it, but it does no harm to ask (especially if you are going to test them out them first)

2) The lifter arms look a little thin where the ferules pass through, with I'm sure will lead to premature wear (ovulation) is that the right word?

3) To knut's remarks, how about bending the cable mount in a nice curve which is "Concentric" :wink: with the spindle? No welding stresses, and would look pretty neat.


One throttle cable (2017)



Cheers,

cliffa.
 
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