Steering pushrod boots - where to source?

[Marty_d]

Hi all,

 

Thinking of boots for where the steering pushrods go thru the firewall.  Some people have used rubber ones but that wouldn't do much in a fire situation.  Other people have suggested using welding gloves with the rods going through one finger... any ideas for a good fireproof boot design?

 

Thanks, Marty

 

 

Edited February 11, 2022 by Marty_d

[cherk]

Marty, I've used some the same appearance , from mem. were I think Jeep transmission boots.

[onetrack]

Marty, Google "Rubber control boot", "Transmission shift boot", "gear lever shift boot", "gear shift boot", and click on "images", and go from there.

[Marty_d]

Thanks guys - then I realised that rubber boots like gear shift ones aren't actually fireproof.  (Guess I could have the boots on the outside for looks, and inside do the welding glove trick!!)

[facthunter]

Pretty grim idea the shafts going through a firewall. The ones on the end of Rack & Pinion steering boxes might be the best available They have to take pretty hot oil and are reasonably compact. Have you got a picture of the set up? I don't really like the idea of complicating the rudder control travel..How are you going to get them on? Nev

[Thruster88]

Depending on the room available fire sleeve (the expensive orange stuff😂) could work. Either clamp it loosely so the shaft slides through or scrunch it up so it can extend. It is quite flexible.

[RFguy]

positive air pressure in the cockpit should keep most things out.

 

 

[skippydiesel]

What do you imagine the boots would do?

 

• Inhibit engine bay fire & its products from entering cockpit ?
• Keep engine noise, fumes, heat from entering cockpit ?
• Prevent draughts ?
• Look cool ?

 

The answers may dictate your next decision and /or boot specifications.

 

[Marty_d]

Bloody hell this thing has lost my started response twice.

 

@cherk - you're right - they're Jeep.

@facthunter - no choice, that's the design.  Threaded rods go from rudder pedals to posts on noseleg so have to move vertically for suspension, forward and back for steering, horizontally (slightly) for lock to lock.

@Thruster88 - I've only seen that orange stuff go up to 30mm.  Not big enough.

@skippydiesel - All of the above.

 

We use welding gloves ($7 from Bunnings) as oven mitts.  My wife informs me that she could cut a pair apart and make them into cones.  I could possibly put those on the engine side for fireproofing and the good looking rubber ones on the cabin side.  

[onetrack]

Marty, that sounds like an entirely satisfactory plan to me, but the durability of constant flexing being applied to the Bunnings gloves would warrant some checking. I'd be looking at some better quality welding gloves.

[RFguy]

I suspect that attention to positive pressure in the cabin would dramatically reduce unwanted gases in the cockpit. I am surprised it's not mandatory.

Most of the aircraft we/I fly have rather ill fitting noises which turn themselves into various neg and pos pressure devices. really needs ram air flow from the front somewhere.  (the rotatable ventilators we use of course are pretty good at that).

 

Use of a Manometer between the cabin and the engine bay (a tube of water)  would turn up some interesting results for most I suspect

[turboplanner]

5 minutes ago, RFguy said:

I suspect that attention to positive pressure in the cabin would dramatically reduce unwanted gases in the cockpit. I am surprised it's not mandatory.

Most of the aircraft we/I fly have rather ill fitting noises which turn themselves into various neg and pos pressure devices. really needs ram air flow from the front somewhere.  (the rotatable ventilators we use of course are pretty good at that).

 

Use of a Manometer between the cabin and the engine bay (a tube of water)  would turn up some interesting results for most I suspect

Depending on the fuselage shape, there's a Bernoulli effect along the sides which is quite strong. On a Cherokee if the hatch isn't locked properly, at a certain speed there's an explosive roar as the door pops open and sits about 50 mm off the closed angle. The door seals are already being subjected to this bernoulli effect, and the lower cabin pressure also allows air vents to work.

[RFguy]

Hi Turbs

interesting effect.  I guess there are a couple of potential problems

- gases in the cowling making their way to the cabin due to higher pressure in the cowling versus lower pressure in the cabin

- external fuselage /cowling exhaust gases  making their way into the cabin .  (well studied and documented).

 

and then as you point out, the need to maintain ventilation.  I reckon the rotatable window side scoops do a pretty good job of positive pressurizing a small cabin but I've never quantified it. They might just bring it back to equalibrium I dunno.

 

 

 

[skippydiesel]

My Zephyr nose wheel steering rods had no gap seals, around the firewall penetration. Winter flying often had a nasty "razor sharp" draft blowing yo my trouser leg. Ugg Boots hep let but were hardly "de rigeur" for walking around an airfield.

 

Rather than partially dismantling the steering system, to install corrugated/concertina boots, I made up 4  felt squares , with a single slot running from centre to on side of each. installed squares on either side of firewall around steering rods using HD air-conditioning aluminium foil tape. Cheap & easy. Worked a treat.

[facthunter]

That system is complex, heavy and dangerous. (not fail safe). Damage to the nosewheel could compromise the rudder action. The plane also has flaperons so the rudder is more important than it usually is. Bowden cables in tension would do the job better with shear pins in case of damage restricting the rudder action,  OR go tailwheel. .Nev

[turboplanner]

2 hours ago, RFguy said:

Hi Turbs

interesting effect.  I guess there are a couple of potential problems

- gases in the cowling making their way to the cabin due to higher pressure in the cowling versus lower pressure in the cabin

- external fuselage /cowling exhaust gases  making their way into the cabin .  (well studied and documented).

 

and then as you point out, the need to maintain ventilation.  I reckon the rotatable window side scoops do a pretty good job of positive pressurizing a small cabin but I've never quantified it. They might just bring it back to equalibrium I dunno.

 

There should not be any transfer between the engine compartment and the cabin if the firewall has been correctly designed.

One facto which leads to these discussions is the number of engineering hours for a mass-produced aircraft vs a low production ultralight - we just can't afford the same engineering hours.

 

I once told a truck manufacturer I couldn't make their cab fit into Australian Regulations. The product manager came back and said "You can do it", so I spent a fortnight, then told him the same and he told me the same. After three months work I found a way to meet the 67 concurrent dimensions and masses target. I apologised about the amount of money I'd charged him and he said, "to cut the cab length by  150 mm would have cost us 100,000 engineering hours."