Control Cable Clearance RV-14 (Mixture)

[Reflex]

Wondering if anybody is using a FM-150 servo with Vans standard exhaust? I'm using this configuration and am having a clearance issue with the mixture cable. The clearance is approximately 1/4". No enough room for a heat shield and may not be enough for encase the cable in fire sleeve.

Thoughts?

See picture below.

 

[Dennis Harm]

Heres a couple of examples of how I did mine. I had room for the heat shields and put fire sleeve around the cable,no problems in 120 plus hours.

 

[Reflex]

Dennis,

Thanks for the quick reply, looks nice. However, you don't have a FM-150 servo. Where your mixture cable runs is where my throttle cable runs. Yes, I have plenty of room for the throttle cable, but not for the mixture cable.

I probably should have put the overall view in my pictures. I'll add them below and to my original post.

Thanks for your input, but I don't see your solution working for the FM-150 as where your cable runs isn't where my problem exists.

 

[Bavafa]

Dennis,

Thanks for the quick reply, looks nice. However, you don't have a FM-150 servo. Where your mixture cable runs is where my throttle cable runs. Yes, I have plenty of room for the throttle cable, but not for the mixture cable.

I probably should have put the overall view in my pictures. I'll add them below and to my original post.

Thanks for your input, but I don't see your solution working for the FM-150 as where your cable runs isn't where my problem exists.

View attachment 63649

View attachment 63651

My first 14A had a FM150 and I was able to put a heatshield and a short piece of fire sleeve over the cable. I will look to see if I can find pictures

 

[MED]

I don’t recall a problem with clearance. These are the only views I have, but it looks like I had plenty of room for a shield and fire sleeve.

 

[Reflex]

I don’t recall a problem with clearance. These are the only views I have, but it looks like I had plenty of room for a shield and fire sleeve.

Med,

Great pictures, it's appreciated. The path of my control cables are exactly like yours. I'm planning putting both a heat shield and a fire sleeve on my cables as you did. However if I do this, the heat shield and fire sleeve will be in contact with each other.

I know pictures don't always tell the whole story, but it looks like your mixture cable is actually touching the heat shield, is that correct?

Many thanks

Fred

 

[MED]

Med,

Great pictures, it's appreciated. The path of my control cables are exactly like yours. I'm planning putting both a heat shield and a fire sleeve on my cables as you did. However if I do this, the heat shield and fire sleeve will be in contact with each other.

I know pictures don't always tell the whole story, but it looks like your mixture cable is actually touching the heat shield, is that correct?

Many thanks

Fred

Maybe? Things move around a bit with vibration. I believe the air gap under the shield makes the shield temperature significantly less than the exhaust, but still hot. The fire sleeve further reduces the temperature of the cable. How long will it last? Dunno, but over 400 hours so far.

 

[DanH]

Anyone know the temperature rating for the blue cable? Pretty sure the old green cables would melt like the Wicked Witch of the West.

Previously mentioned installing a thermistor a fat thumb's width from an exhaust pipe, under the engine, on the bottom of the throttle and mixture cable shielding. Results are interesting. Temperature hit 200F before I could get oil temp up to my customary 100F for takeoff. Top of climb was 255F and it stayed there for the next 30 minutes while I ran some other tests. After landing and hot taxi, lack of airflow ran it all the way up to 300F.

Best I know, pipe temperature at this downstream location is lower than typical for a headpipe closer to the cylinder. I'll move it around to measure some other locations.

Adding an insulation layer under some foil tape will improve the heat shields, and a reflective layer on the outside of the fire sleeve (shiny aluminum tape again) will also improve performance.

 

[MED]

Med,

Great pictures, it's appreciated. The path of my control cables are exactly like yours. I'm planning putting both a heat shield and a fire sleeve on my cables as you did. However if I do this, the heat shield and fire sleeve will be in contact with each other.

I know pictures don't always tell the whole story, but it looks like your mixture cable is actually touching the heat shield, is that correct?

Many thanks

Fred

It is hard to tell, but it looks like your cables are not mounted as parallel as mine are. Is it possible that brings the one cable closer to the exhaust? Might just be a perspective thing, but there are multiple holes in the support, which might give you more clearance.

 

[Reflex]

Anyone know the temperature rating for the blue cable? Pretty sure the old green cables would melt like the Wicked Witch of the West.

Previously mentioned installing a thermistor a fat thumb's width from an exhaust pipe, under the engine, on the bottom of the throttle and mixture cable shielding. Results are interesting. Temperature hit 200F before I could get oil temp up to my customary 100F for takeoff. Top of climb was 255F and it stayed there for the next 30 minutes while I ran some other tests. After landing and hot taxi, lack of airflow ran it all the way up to 300F.

Best I know, pipe temperature at this downstream location is lower than typical for a headpipe closer to the cylinder. I'll move it around to measure some other locations.

Adding an insulation layer under some foil tape will improve the heat shields, and a reflective layer on the outside of the fire sleeve (shiny aluminum tape again) will also improve performance.

Dan,

I used cables from McFarlane Aviation. Their specs state the "blue cables" have a working temp of -65F to 450F.

I'm just trying to get enough room to put both a heat shield as you depicted with Fiberfrax and a fire sleeve. I can get them to fit, but the firesleeve is touching the heat shield.

Thanks,

Fred

 

[Reflex]

It is hard to tell, but it looks like your cables are not mounted as parallel as mine are. Is it possible that brings the one cable closer to the exhaust? Might just be a perspective thing, but there are multiple holes in the support, which might give you more clearance.

Med,

Thanks for keeping in touch with this. Yes, I think it's a perspective thing. After very close examination of you pictures, it appears that we're using the same holes.

Thanks,

Fred