How important is stroke on throttle/mixture/prop cables.

[akschu]

I am looking to order a McFarlane Vernier-Assist throttle cable and noticed that the stroke is 3.5" but my airflow performance FM-150 only needs 2.5" of stroke.

I also noticed that ACS products makes RV specific control cables with 2.25 or 2.5 stroke for the prop and mixture.

What I don't understand is why there are custom shorter stroke cables for RV's. Wouldn't a standard A-750 control (with a 3.375 stroke) work on an RV with the cable hitting the stop on the fuel servo making the control stop at 2.5" ?

Please help me understand why it would be desirable to have a custom cable with shorter throw when a cable with a longer throw just simply stops short from coming all of the way out.

Thanks,
Matt

 

[Desert Rat]

I guess one reason might be the length of the rigid section right behind the knob. Don't know which RV you're building, but on the side by sides, you secure the cable to the lower edge of the sub-panel immediately forward of that section with adel clamps. I'm not sure without looking under my panel what an extra inch of rigid tube sleeve might do to that arrangement.

 

[RV7 To Go]

I guess one reason might be the length of the rigid section right behind the knob. Don't know which RV you're building, but on the side by sides, you secure the cable to the lower edge of the sub-panel immediately forward of that section with adel clamps. I'm not sure without looking under my panel what an extra inch of rigid tube sleeve might do to that arrangement.

Yep, the location for the bulkhead mounts is farther back with the longer stroke cables. I just found this out with the ACS cables I purchased for my 8. Had to modify the bulkhead cable mounts at both ends to accommodate the longer (3.5") stroke cables. The cable travel was limited by the quadrant or the carb/governor arm throw.

 

[Kyle Boatright]

The more bends you have in the cable , the less the effective throw will be. On my RV-10 (in particular), the stock throws barely worked and it took a fair amount of fine tuning to enable all of the controls to hit both the max and min stops.

 

[climberrn]

I ordered a 3.375 stroke for my forward mounted governor in a custom length. The vans bracket wouldn’t work since the shaft is significantly longer. Tried to make a longer bracket but it caused interference with the upper cowl. Ended up ordering the 2.5” stroke. Stick with the 2.5 stroke if using the vans brackets.

 

[Sam_B]

The quadrant models may have something to do with it. I ran into this on my -8 last winter:

MA-4-5 Mixture Throw on RV-8

Hey everyone, I’m hoping to take advantage of the collective brain power and experience of this group. I’m just getting back to building after several months of life getting in the way and man does it feel good! But I digress, I ran into a snag this evening while working on getting the mixture...

vansairforce.net

 

[koupster]

my airflow performance FM-150 only needs 2.5" of stroke.

Matt,

Don't plan on a cable with a 2.5" stroke giving you a full 2.5" at the FM-150. You should have a small "cushion" at the most forward travel point at the cockpit end. Also, a small bit of travel is lost due to the difference in the OD of the cable and the ID of the housing.
My second hand RV-6A came with a throttle cable withat had a throw that was to short for full travel at the carb.

 

[Reflex]

I am looking to order a McFarlane Vernier-Assist throttle cable and noticed that the stroke is 3.5" but my airflow performance FM-150 only needs 2.5" of stroke.

I also noticed that ACS products makes RV specific control cables with 2.25 or 2.5 stroke for the prop and mixture.

What I don't understand is why there are custom shorter stroke cables for RV's. Wouldn't a standard A-750 control (with a 3.375 stroke) work on an RV with the cable hitting the stop on the fuel servo making the control stop at 2.5" ?

Please help me understand why it would be desirable to have a custom cable with shorter throw when a cable with a longer throw just simply stops short from coming all of the way out.

Thanks,
Matt

I installed my customer vernier assist throttle from McFarlane last Sunday on my FM-150. It's a nice piece of work. Regarding the throw, it doesn't really matter what the stroke of the cable is as you want the stops on the FM-150 to be what causes your throttle (or mixture and prop) cable to hit the end...not the cable itself. Example, that's why you want at least 1/16" to 3/32" gap between the knob and the panel when the controls are pushed forward.

 

[akschu]

I guess one reason might be the length of the rigid section right behind the knob. Don't know which RV you're building, but on the side by sides, you secure the cable to the lower edge of the sub-panel immediately forward of that section with adel clamps. I'm not sure without looking under my panel what an extra inch of rigid tube sleeve might do to that arrangement.

Thanks for this. That helps me understand what the deal is.

I'm not actually building an RV but post on non-RV specific threads because there is so much knowledge here. It's been very helpful with a lot of decision making and learning.

In this case I am using the RV-10 baffling so the RV specific prop control will work with the stock bracket, otherwise I think I'll need to modify it to make it work. As for the panel, I have all of the space in the world, so that's not an issue.

Thanks!