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  #1  
Old 04-24-2019, 07:52 PM
WingnutWick's Avatar
WingnutWick WingnutWick is offline
 
Join Date: Jun 2013
Location: Fresno, CA (KFCH)
Posts: 268
Default So close yet so far - Throttle and Mixture cable woes.

So after the new RV-6As mixture bound and bent for the second time I decided to take it upon myself to replace the quadrant style cables that were wrapping around the carb to make the direction of travel correct and go with the standard RV-6 setup. I ordered the RV-6 throttle and mixture cables from vans and the RV-6 O-320 bracket.

Woe #1: the bracket did not fit correctly and I had to cut and bend it to meet it from pressing against the oil pan. Then I had to dremel out a hole for the oil drain to go through. Not pretty but figured it?d due the trick. I chalked the bracket not fitting great due to the motor being an H2AD and kind of an odd ball engine, but I don?t really know.

Woe #2: Drilling the holes. With everything mounted on I couldn?t use a template so I had to eyeball it. The battery is in the inside of the cockpit centered between the rudders and in front of where they say to put the mixture control so I elected to have the mixture come out to the right of the battery below the throttle thinking that bend wouldn?t be enough to hamper the movement of the control. A royal PITA working under the dash like that with my 6ft4 frame. Plus there is this shield that is behind the battery that I had to work through.

Woe #3: Finally got the cables routed and through the firewall. And all the hardware put in only to find that the throttle cable doesn?t reach the bracket hole, let alone the throttle arm to allow for full throttle. This is bizarre because it?s pretty much B-lining straight from the dash to the firewall and to the carb. Furthermore the mixture doesn?t want to travel all the way out (lean). Not sure if that is binding due to the small curve but I?ve seen more aggressive curves on other?s planes work.

Before I went putting more holes in the firewall I want to check in and see if anyone know what the heck is going on here!? Inputs, insights, suggestions always very much appreciated!!

Thank you all!

Charles




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F-18E/F, Mk.58, CF-5
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  #2  
Old 04-24-2019, 07:57 PM
Kyle Boatright Kyle Boatright is offline
 
Join Date: Aug 2005
Location: Atlanta, GA
Posts: 4,671
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Measure twice, buy cables once. Honestly, it looks like you just need to measure how far short your cables are and buy longer ones.

You're not the first. I bought the standard RV-10 cables. Unfortunately, my fuel injection setup requires longer cables. So I have about $150 in unused cables sitting in the shop.
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2001 RV-6 N46KB
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  #3  
Old 04-24-2019, 08:18 PM
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WingnutWick WingnutWick is offline
 
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Location: Fresno, CA (KFCH)
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Default :(

It?s looking like that?s going to be the case. Unfortunately I thought I was safe buying the standard application cables and routing them within inches of their designed routing, so I?m not sure where the disconnect has come from? I would think more would have this issue if those cables weren?t the correct length?

Quote:
Originally Posted by Kyle Boatright View Post
Measure twice, buy cables once. Honestly, it looks like you just need to measure how far short your cables are and buy longer ones.

You're not the first. I bought the standard RV-10 cables. Unfortunately, my fuel injection setup requires longer cables. So I have about $150 in unused cables sitting in the shop.
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  #4  
Old 04-24-2019, 08:28 PM
Kyle Boatright Kyle Boatright is offline
 
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Location: Atlanta, GA
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Quote:
Originally Posted by WingnutWick View Post
It?s looking like that?s going to be the case. Unfortunately I thought I was safe buying the standard application cables and routing them within inches of their designed routing, so I?m not sure where the disconnect has come from? I would think more would have this issue if those cables weren?t the correct length?
With a different engine or a different sump and carb (or FI) there can be meaningful changes in geometry or distance from what the factory considers "stock". On my -6, I replaced the cables about 5 years ago and simply pulled the old ones, measured, and ordered direct replacements.
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  #5  
Old 04-24-2019, 08:45 PM
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Mark33 Mark33 is offline
 
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Location: Baton Rouge, La.
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Default

I’m not sure how the control cables of a 6-A are suppose to run, but from your pictures it looks like you have some pretty serious bends going on there.

It appears as though your cables are coming out of the bracket that’s under the panel and running forward toward the firewall and then making a hard bend down in front of your peddles and then making another hard bend next to the floorboard and then exiting the firewall.

If it were me, I think I would have kept my cables as high as possible (as straight of a shot as possible from the control bracket to the firewall) and then have the cables droop down as needed to make as straight of a shot as possible to the throttle and mixture.

It just looks like you’re loosing a lot of cable length by having them go up and down a lot and all of those bends may also be hampering their movement.

Mark
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  #6  
Old 04-24-2019, 10:24 PM
lr172 lr172 is offline
 
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Location: Schaumburg, IL
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Quote:
Originally Posted by WingnutWick View Post
It’s looking like that’s going to be the case. Unfortunately I thought I was safe buying the standard application cables and routing them within inches of their designed routing, so I’m not sure where the disconnect has come from? I would think more would have this issue if those cables weren’t the correct length?
The standard 6 throttle cable is on a vertical panel and much lower than yours (less vertical drop and therefore less length required). Your cable is in the std position for a 7. Therefore you would order the cable that is std for the 7, which is 2" longer than what is standard for the 6. From the pics, you seem to be in the neighborhood of 2" short.

Buyers need to do a fair amount of research, as builders can make a lot of modifications from the std plans.

You have an odd looking arm on the mixture control. You will probably need to make a shorter one. Measure the distance of the hole in the arm from rich to lean and then compare to the travel spec for the cable. Then measure at what point on the arm the rich to lean hole difference will match the cable's travel. (as distance from hole to pivot shortens, so does the total linear movement between rich and lean) Put new hole there. (be mindfull of edge distance between old and new hole.

It looks like the builder made a custom aluminum arm. I would feel much better with a steel piece in that application or at least 3/16" or 1/4" al. A lot of vibration in that area and aluminum can fatigue with vibration. You don't want that connection to break in the air.

Larry
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Last edited by lr172 : 04-24-2019 at 10:56 PM.
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  #7  
Old 04-24-2019, 11:23 PM
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az_gila az_gila is offline
 
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Location: 57AZ - NW Tucson area
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Smile

The throttle cable will just reach if you flip the O-032 mounting bracket on the panel the other way around...
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  #8  
Old 04-24-2019, 11:57 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Quote:
Originally Posted by WingnutWick View Post
Furthermore the mixture doesn?t want to travel all the way out (lean). Not sure if that is binding due to the small curve but I?ve seen more aggressive curves on other?s planes work.
I think your mixture travel problem is probably related to the extension that appears to have been added to the mixture control arm.
The standard mixture cable has just enough travel to work when connected to the standard length mixture control arm. Making the control arm longer essentially made it need to move a farther distance between idle cut-off and full rich.

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  #9  
Old 04-25-2019, 12:45 AM
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az_gila az_gila is offline
 
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Quote:
Originally Posted by rvbuilder2002 View Post
I think your mixture travel problem is probably related to the extension that appears to have been added to the mixture control arm.
The standard mixture cable has just enough travel to work when connected to the standard length mixture control arm. Making the control arm longer essentially made it need to move a farther distance between idle cut-off and full rich.
My mixture arm is a standard one and the Vans cable does not quite close it on lean cut off.

Following other comments on VAF I set it up for full on (with a cushion) and let the lean cut off end not quite close.
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Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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  #10  
Old 04-25-2019, 08:37 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by az_gila View Post
My mixture arm is a standard one and the Vans cable does not quite close it on lean cut off.

Following other comments on VAF I set it up for full on (with a cushion) and let the lean cut off end not quite close.
Maybe it is something different with your carb. or available cable travel.
All 3 of the carb equiped airplanes I maintain (a nix of O-320 and O-360... 1 of them my own 6A) work normally but there is no extra travel of the cable. So as I already mentioned, if the arm is made longer the cable will not be able to move it through the full range of travel.
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FAA/DAR
RV-6A (aka "Junkyard Special ")
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