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throttle cable throw help

echostar7

Active Member
im changing to MA-4SPA as I have mentioned in other threads,
I have an A-1550-0430 Throttle cable from aircraft spruce, it is push-pull bulkhead type cable at both ends with 3.37" stroke which worked for the previous carb geometry that I had (not same carb) and works fine firewall aft. Now with MA-4SPA with vans VA-149-320 bracket, and it seems like it has too much throw / is too long past the bulkhead nuts? it is impossible to thread on a rod end bearing and attach to the throttle arm with hardware at fully retracted (idle)it is at least 1" too long to attach to the carb.

what is the right throttle cable lengths what should I be looking to order. or maybe put another way what cable would work with the VA-149-320 bracket mounting and MA-4SPA. I'm not sure where to start with this.
https://imgur.com/grVdv7b bracket fitting to throttle arm middle hole (full throttle set)
https://imgur.com/Fb0XdFa full extension throttle cable
https://imgur.com/oKtGbD8 idle extension throttle cable
 
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You have plenty of "throw". The hrottle cable end dimensions are now not optimal.

- You can make new connections points at the forward end if room is available.
- You can order a new cable with the desires dims from McFarlane.

or possible mod the existing cable. From your pix, you might have room to:

- Center everything, Carb lever, throttle position.
- Verify any rod ends and/clevises are centered between bottoming out and the witness hole,
- reconnect the cable at the throttle end and re-center.

- Now measure the distance delta, center-to-center at the carb connection. Remove that much of the cable end and rethread.

Lots of potential ways but that's all I can think of via your pix. Good luck.

Edit = ensure any range of motion is only limited by the carb mechanical limits.
 
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Matt,

I had a similar situation when I installed an RV-10 throttle quadrant in my RV-14. I measured and ordered new cables, but still had trouble with the throws. I replaced the mixture and governor arms to adjust for the throw lengths.
 
You can modify the bracket to move the mount area aft a bit or cut off some of the steel shaft and re-thread (pretty sure it is just 10-32) or find a better fitting cable.

Have no idea on the dimensions of all the different brackets.

Larry
 
My thought was I'm not reinventing the wheel here or should not need to. The bracket is the standard one sold by vans for a carbed o320, I have that and the carb. If I knew what the dimensions were for the cable that normally gets used for this setup I could have one made but for throttle quadrant setup.

Side note I did try cutting new threads on the threaded rod but it was very difficult to cut with a hand die and gave up after cutting 1-2 new threads. Because it wants to spin internally
 
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My thought was I'm not reinventing the wheel here or should not need to. The bracket is the standard one sold by vans for a carbed o320, I have that and the carb. If I knew what the dimensions were for the cable that normally gets used for this setup I could have one made but for throttle quadrant setup.

Side note I did try cutting new threads on the threaded rod but it was very difficult to cut with a hand die and gave up after cutting 1-2 new threads. Because it wants to spin internally

Cable aside, you changed the configuration. No one here can alter the laws that govern kinematics. Additionally, the cable should freely rotate inside of the shield. If the end weren't secured when your tried to cut new threads, you twisted the cable to an unknown degree and it's no longer trustworthy IMO. I'd find someone local with the appropriate experience/license/tooling/etc and get a new cable on order. Once again, just my opinion.
 
Cable aside, you changed the configuration. No one here can alter the laws that govern kinematics. Additionally, the cable should freely rotate inside of the shield. If the end weren't secured when your tried to cut new threads, you twisted the cable to an unknown degree and it's no longer trustworthy IMO. I'd find someone local with the appropriate experience/license/tooling/etc and get a new cable on order. Once again, just my opinion.
The vans builder support line recommended ca push-pull so I will give them a try.
 
Side note I did try cutting new threads on the threaded rod but it was very difficult to cut with a hand die and gave up after cutting 1-2 new threads. Because it wants to spin internally

You need to secure it to tap threads. Take a chunk of Alum and drill a 3/.16" hole in then slice it in half at the center of the hole. Then use it in the vice to hold the rod while tapping.

As mentioned above, you may have trashed the internals of the cable if you let it rotate much. Throttle cables usually rotate at the knob end, so very possible that no damage was done.

Larry
 
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