Transmission gear shifting cable - backlash reduction

[sivarajsrj]

need help in reducing the backlash of the cable. our transmission is actuated by cables & the cable is taking 180 turn one side is connected to the gear shifter/stick and other side is connected to the transmission. due to 180 degree bend there is a high free play/magnitude of the backlash. this is affecting the precision of gear shift feel. i know reducing the cable internal clearances (ID OD) will reduce the backlash but doing which is increase the cable friction. is there any other alternative option available? is there any method to preload the cable to avoid freeplay?

 

[GregLocock]

replace the cable by a pair of push pull rods and a bellcrank.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[BrianPetersen]

Or redesign the linkage (at either end, or both ends, as necessary) to eliminate the need for the cable to do a 180 degree turn.

 

[Tmoose]

Have you watched the components while shifting to confirm there is no lost motion at the attachment points of the inner cable AND outer conduit/housing/sheath ?

 

[Mongrel]

You could look into the Australian BA/BF/FG Falcon cars as an example of doing what you describe successfully. They run a cable from the shifter in the centre of the car, forward through the firewall, then looping back to connect to the side of the gearbox. This works just fine and lasts quite well; the weak link is the plastic connection between the cable end and the shift linkage on the box.
They achieve this with a hard plastic outer casing, roughly 8mm OD, and a flexible metal rod inside, rather than a cable. I haven't measured one but estimate 4mm diameter on the rod. Securing the plastic housing at both ends and using ballpoint connections gives a very good shift feel with no slop. Adjustment is handled with a slotted end at the gearbox; the plastic ballpoint socket can be moved along the slot and clipped into place.

Edit: you could also investigate industrial, agricultural, and trucking applications, particularly with older PTO drive engagement cables which use a similar idea, often a thin, flexible steel wire inside a coil shearing. These also last well and with no slop, if the ends of the sheathing are pinned into place properly.

 

[Tmoose]

"After joining Eng-Tips Forums on December 13, 2019, I've logged in 1 times. My last login was on Friday, December 13, 2019."

OP logged in to post his question 2 weeks ago, and never returned.

 

[gruntguru]

They keep doing this don't they? Oh well, I guess it provides us with topics to discuss among ourselves.

je suis charlie

 

[JayMaechtlen]

Learning opportunity for some of us, too - I understand they are using the cable to transmit a twisting motion (and presumably a push-pull as well?)
I wouldn't have been devious/brave enough to try that.
The Falcon scheme sounds quite clever. I assume the twisting motion doesn't require a lot of force, so using a really long torsion bar to turn the device still works?


Jay Maechtlen

http://www.laserpubs.com/techcomm

 

[BrianPetersen]

Dunno about the Falcon but the VW and Fiat ones that I've owned have had one push-pull cable for the fore-aft motion and a second push-pull cable for the side-to-side motion.

 

[Mongrel]

That cable is used on an automatic transmission, so no twisting. I had read the OP as a similar situation, quoting a 180 degree motion.
In my experience, controls requiring torsion use either a solid bar, or two cables as per Brian - the side-to-side motion being provided by a simple 90 degree lever.
Academic I know, given the OP posted then vanished...