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MarkCFI

Well Known Member
I need to shorten this throttle cable extension (not sure what it’s called) by about 1/8” of an inch.

I had to adjust the throttle arm on new carb due to some geometry issues ( cable hits oil pan at full throttle ) and it needs to be shortened by 1/8-1/4”.

Or can these be cut ?

IMG_0259.jpeg
 
MarkCFI said:
I need to shorten this throttle cable extension (not sure what it’s called) by about 1/8” of an inch.

I had to adjust the throttle arm on new carb due to some geometry issues ( cable hits oil pan at full throttle ) and it needs to be shortened by 1/8-1/4”.

Or can these be cut ?

View attachment 61640
Click to expand...

Your throttle cable "extension" is nothing more than a piece of aluminum tubing that has been cut to length, and tapped on both ends to accept 10-32 threads (from the rod end and the actual end of the throttle cable). So yes, you can cut it to the length needed. You might have to re-tap the cut end deeper so the threaded in part will still fit. While doing that, make the extension short enough so that you have a few threads showing at each end.....to allow for future shortening adjustments. In the photo it looks like both ends are fully threaded in........and the cable is still too long.

Having said all that, my personal preference would be to determine the actual cable length required, and order a new cable to fit. That makes one fewer threaded connections in the system (ie: one less connection to fail.....also, a longer cable might help solve your "cable touching the oil sump at full throttle" problem).

Maybe one of the A&Ps here will chime in as to whether such a cable extension is acceptable/not acceptable as a general practice.
 
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Not an AP, but I wouldn’t accept this in my airplane. Get a proper cable.
You may need to modify or replace your bracket if geometry is the issue.

…and, for the OP, just to be picky, cars have oil pans, airplane engines have sumps. :)
 
If you can get a side view pic of your cable routing to the carb, there are lots
Of folks here that can help you determine if you need a different carb bracket or modification.
 
JonJay said:
If you can get a side view pic of your cable routing to the carb, there are lots
Of folks here that can help you determine if you need a different carb bracket or modification.
Click to expand...
I can get a picture.

a description is that there is a piece of aluminum channel with a hole drilled in it attached with u-bolts to the engine mount.

It’s not like any of the other brackets I’ve been able to search for which look like a bent piece of flat metal that at times is bolted to the “sump”.

Given the spacer that lengthens the cable I’m thinking that maybe if I used a new mount where the large nuts clamp the cable it might actually be the correct length?

Is there a method to determine how long the cable should be and what the distance should be between the cable bracket and throttle?

Pictures to follow. It may take a few days as the hangar is a bit of a drive.
 
At a minimum it looks like I will need to replace the end bearings with a female thread end bearing. What is the standard size end bearing that I would need to order?
 
You may need a proper extension to replace the aluminum tubing in the picture. Aircraft Spruce has this:
www.aircraftspruce.com

Extensions For Threaded Controls | Aircraft Spruce

Extensions For Threaded Controls Use these stainless steel extensions for moderate length adjustments to stock length controls. Stocked with one male and one female threaded end. Also available with two female threaded ends. Th...
www.aircraftspruce.com www.aircraftspruce.com

Or follow the suggestion and replace the current control cable with the new control cable with the appropriate length.
 
PhatRV said:
You may need a proper extension to replace the aluminum tubing in the picture. Aircraft Spruce has this:
www.aircraftspruce.com

Extensions For Threaded Controls | Aircraft Spruce

Extensions For Threaded Controls Use these stainless steel extensions for moderate length adjustments to stock length controls. Stocked with one male and one female threaded end. Also available with two female threaded ends. Th...
www.aircraftspruce.com www.aircraftspruce.com

Or follow the suggestion and replace the current control cable with the new control cable with the appropriate length.
Click to expand...

I think what I’m going to do is move the existing bracket or install a new bracket that would align the throttle cable to throttle geometry.

I think the actually throttle cable may be the correct length it’s just mounted too far from the throttle lever, hence the extension in there now.

Seems like that’s the correct thing to do.

Appreciate all the advice. It’s all a good learning experience and when we get to the Firewall forward section of the RV-8 we are building I’ll have some experience with this.

Thanks
 
This is a picture of what I currently have as throttle bracket and mixture bracket.

I have an email in to VANS asking which of the cable brackets they recommend for a lycoming O-320 D3G and RV-6. They seem to have two options. Both clamp between the carb and sump and provide a location to affix the cables for the carbs. Once I get the proper part to order will do so and then order new cables as required.

If someone knows which of the brackets are correct that would be great although I can wait for vans to respond. Any third party options appreciated as well

Thanks again for the advice.

IMG_0260.jpeg
 
MarkCFI said:
This is a picture of what I currently have as throttle bracket and mixture bracket.

I have an email in to VANS asking which of the cable brackets they recommend for a lycoming O-320 D3G and RV-6. They seem to have two options. Both clamp between the carb and sump and provide a location to affix the cables for the carbs. Once I get the proper part to order will do so and then order new cables as required.

If someone knows which of the brackets are correct that would be great although I can wait for vans to respond. Any third party options appreciated as well

Thanks again for the advice.

View attachment 61968
Click to expand...
Yep, you definitely need the correct bracket from Van's. The engine control cable sleeves need to be attached to the engine at the engine end (hope that makes sense)....that is, they need to be able to move with the engine as it vibrates. Yours are currently mounted to the engine mount which is rigid mounted to the airframe. The result is any engine movement has to be taken up by the short solid cable end running from the engine mount to the throttle arm. Not a good setup. And...the same thing is happening for the same reason with the mixture cable.

And (just an aside FYI) the current bracket shown is not aircraft grade aluminum (based on the sharp inside corner bend). It is probably the soft stuff (think cheap window frame grade) sold at hardware stores. Aluminum alloys used in aircraft are quite a bit stronger than the soft stuff. Then there's the hardware store u-bolt and nuts holding it in place........but that's just piling on at this point ;).

Step one: install the correct bracket. Step two: get the correct length throttle control cable.

Remember, there is one and only one throttle control cable on the engine.....it needs to be a very high reliability setup.
 
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Concur. Working with VANS to identify the correct part. It looks like it’s backordered. I may put out a cry in the wilderness in the classified section to see if anyone’s got one once I know what the vans status is.

Thanks.
 
MarkCFI said:
Concur. Working with VANS to identify the correct part. It looks like it’s backordered. I may put out a cry in the wilderness in the classified section to see if anyone’s got one once I know what the vans status is.

Thanks.
Click to expand...
Vans has the recommended length for the various engine control cables. I think I found the paper plan has the length for the RV8. You can order a custom made cable from Aircraft Spruce and it provides a nice webpage interface so you can pick and choose the end fittings that will fit your aircraft.
 
The part number at vans is VA-149-320-PC KIT

It shows as backordered. I’m not married to the Vans part if there is a 3rd party vendor with equivalent.
 
I have the correct bracket inbound thanks to another member..

One really dumb question I have as a prepare to install.

It looks like this bracket clamps between the carb and the sump. Does this require two gaskets. One between the carb and the bracket and then one between the bracket and the sump?

Or just a single gasket?
 
MarkCFI said:
I have the correct bracket inbound thanks to another member..

One really dumb question I have as a prepare to install.

It looks like this bracket clamps between the carb and the sump. Does this require two gaskets. One between the carb and the bracket and then one between the bracket and the sump?

Or just a single gasket?
Click to expand...
You don't really want air leakage in that location, on either side of the bracket. Get two new gaskets. One between the sump and the bracket, one between the bracket and the carb. Aircraft Spruce carries both Lycoming 66224 or Superior SL66224.
 
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