Control Cable Firewall Bushing Size?

[Lars]

Originally Posted by dan

I'm a little late to the game here, but I want to echo what Smokey said. I used the one-hole eyeballs on my RV-7, and I am kicking myself. I've had to replace all 3 cables more than once, and I'm currently (this morning) in the process of replacing my mixture cable. Those one-hole eyeballs are such a pain in the fcuk1n6 a$$.

Over time I made a little "wrench" out of 1/8" thick aluminum that lets me hold the base so it doesn't rotate while unscrewing the locking ring, but the locking rings themselves strip. And since one time I had a locking ring vibrate loose on me, I've been using loctite on 'em, which makes matters so much worse when it comes time to remove them. I can't even begin to tell you how much time I've wasted on these stupid things.

All I can say is, the one-hole eyeballs are seriously ANTI easy maintenance. Totally nonstandard, and I will NEVER use them again.

I'm switching to the 6-screw design immediately. I haven't done it yet because switching, in and of itself, is now a pain in the a$$ since my one-holes are pretty close to the engine mount down tube, and the holes are different sizes...I need to make a sandwich plate type thing with bad access. I've been lazy until now, but screw it. I do NOT want to deal with these stupid things anymore.

Hope this helps maybe one builder out there.

I'd heard about the galling issue from someone else, so clicked on the 6-screw option when I bought mine.

Since I had four to install I wasn't excited about using the supplied paper template, so I made a drill jig out of a piece of scrap steel bar. Much easier. Might be helpful also if you are groveling in a tight space.

[JonJay]

This is a classic example of how you can take a simple perfectly working solution, like a hole with a grommet, and add some nice $$ to the cost of your project. Now, I am not saying the fancy eyeballs are not worth it, or judging anyone for spening the money to put them in. God knows I spent my fair share of $$ on things I thought where important.
I think I will start another thread on all of the things that one could "upgrade". That list is long..... and expensive, and by the time I was done I have no doubt that my build would be north of $100k.
On the positive note, that is part of the fun and freedom of building your own experimental airplane.

[dan]

Originally Posted by JonJay

This is a classic example of how you can take a simple perfectly working solution, like a hole with a grommet, and add some nice $$ to the cost of your project. Now, I am not saying the fancy eyeballs are not worth it, or judging anyone for spening the money to put them in. God knows I spent my fair share of $$ on things I thought where important.
I think I will start another thread on all of the things that one could "upgrade". That list is long..... and expensive, and by the time I was done I have no doubt that my build would be north of $100k.
On the positive note, that is part of the fun and freedom of building your own experimental airplane.

You are absolutely correct...except consider the scenario where the cable needs to pass through the firewall at, say, a 30-40 degree angle. I just didn't have warm fuzzies about using a grommet & sealant. I wanted the cable to be held a little more firmly. Had I just used the traditional eyeballs from the start (as opposed to the one-hole eyeball), I wouldn't be posting this right now...

[flion]

Originally Posted by rocketbob

There are thousands of C-172's flying with the throttle cable penetrating the firewall with nothing more than a hole drilled thru it.

Another good reason to have an RV instead of a Cessna... I could probably have gone with a simpler penetration on the throttle and mixture, but the prop cable had to do a 90 degree turn to get to the governor and I did not like the tightness of the turn if it began forward of the firewall. Better to make a wider turn that passed through the firewall at an angle. Fortunately, I didn't consider an aluminum eyeball to penetrate the steel firewall.

By the way, I found the steel eyeball self-jigging; a 1/16" bit fit easily into the nuts without harming the threads. Then I drilled the piloted holes out to 1/8", which is still well covered by the nut plate.

[rzbill]

OK, so for many months I have been doing mental gymnastics with the issue of firewall passthroughs for the engine control cables. The root problem was I didn't have any cables in my hand to measure and the data on Spruce's site plus postings here did not add up.

Dimensional issues solved today. I recieved my order of Vans control cables last night for 7A, M1B with const speed.

They are all custom cables from ACS Products:

Throttle = A-800BL0505-V
Mixture = A-1760-20-0505-V
Prop = A-1760-30-0480-V

The important part is the "V" since it obviously includes custom specs from Van. One of the custom features is inclusion of the polyolefin coating on the cable sheath. This increases the overall cable diameter to approximately 0.267" (measured by me and posted by others previously) vs the uncoated bare metal sheath diameter of .250 (per conversation with ACS Products today). If one orders an ACS brand cable from Spruce, it will be bare unless the coating is specified as an option.

SO, on to the eyeball selection:
It is obvious to me now that the eyeball sizing chart from Spruce is tailored to the BARE cables, not the coated cables. For instance, the steel SE961-S called out for A-800 and A-1760 cables has an ID of .240 which I take to mean they want a .010 grip on the bare cable. These steel eyeballs cannot be resized, so the selection has to be correct from the get-go.

At this time, I have not made the decision whether to compensate for the plastic sheath diameter by ordering a .250 or even .260 diameter ball, or simply remove a short section of plastic sheath and use the specified .240.

While writing this, I am leaning towards cutting the plastic sheath so I can clamp directly on the wound wire sheath.

I hope this diatribe helps others that are thinking on the same issue.

[rv8ch]

My throttle/mixture/prop cables came from Van's with the FWF kit, and the diameter is about 0.336. The outside is some kind of green plastic, so I could probably squeeze it into a 0.250 eyeball, but I would only recommend the 6-hole version, not the evil one hole version.



Has anyone else used the steel 6-hole eyeball grommet with the Van's cables?

Another option is to use this "STAINLESS STEEL
FIREWALL PENETRATION KIT":



I am probably over-thinking this, but I don't feel comfortable with the way the plans describe plastic grommets as a firewall penetration.

[Lars]

I've now officially installed and used 4 of the 6-screw steel eyeballs with various Van's-supplied cables. Easy. Dan's previous comments about cables angling through the firewall at something other than 90 degrees apply accurately to my situation. Not to mention that similar low-budget firewall penetrations I've had in automotive hot-rod applications tended to not live very long. Eye like my eyeballs

Sounds like you have the older marine-style cables that Van's used to supply. The throttle, mixture and prop control cables I received from Van's all have a grey plastic sheath on the outside, and are roughly 1/4" in diameter. They are marked as being made by ACS products, and fit the .250" diameter eyeballs easily.

[DanH]

http://www.vansairforce.com/communit...79&postcount=3

Cheap and easy to fabricate, very effective.

[tonyjohnson]

Let me see if I understand the situation if you have the green marine style cables from vans:

The diameter is about .337

None of the eyeballs come in that diameter.

You should not use the aluminum ones

You cannot drill out the Steel ones

I cannot weld.


So, what do you do?

[ronschreck]

Originally Posted by tonyjohnson

Let me see if I understand the situation if you have the green marine style cables from vans:

The diameter is about .337

None of the eyeballs come in that diameter.

You should not use the aluminum ones

You cannot drill out the Steel ones

I cannot weld.


So, what do you do?

Use the six-hole aluminum one and drill it out. If you have a fire that burns through that solid aluminum ball you have other, more serious things to worry about.