Thorp Air Command - T18.net

I have pilot and pax side brakes. This Hoof brand pressure valve (with the red ID plate on it) currently connects the brake to the pilot and pax pedals. I have a reservoir on all 4 pedals. (repeat this setup for the right brake system too obviously). What is the benefit (if any) of having this valve T sysyem over a standard T (like below ) in order to tie the pilot/pax/brake system together? Which way have you built your brake system?

Unless you just want to fill your co-pilots master cylinder each time you mash the brakes, you should leave the check valve in the system.

_________________
Bob Highley
N711SH
SN 835
KLAL

Haven't heard of this valve before ? Sound like a one way check valve. Who ever has the biggest foot on the pedals overides the pedal pressure on the other set of brakes ? Looks like an expensive unit to overhaul ?

RB

Thats a good point Bob. Rich, how is your brake sytem "T"ed together where the pilot/pax/brake line all meet?

Theres nothing wrong with the valve that I have on mine. Its working properly. I just couldnt think of why it was on there. I did find a similar unit on a salvage yard website for $50.

I only have Captain side brakes.

RB

That is a shuttle valve. A piston slides back and fourth depending on which side brakes are pushed. The same valve is used in some King Air's I have worked on. You should have two of them. Bleeding the brakes is a little tricky. Push on the pilots brakes, then bleed Left and right break. Then push on the copilots brakes to move the shuttle valve and bleed the brakes again. I have seen the valves stick on the king air's beceause they were never used on the copilot side. I would recomend actuating the brakes on the right side every so often.

Jeff

I forgot to answer your question. A tee fitting will not work because you will blow the fluid out the top of the other side master cylinder. You would have to get two new master cylinders without resivores that are approved for series operation and put them on the pilots side. The copilot side master cylinders become the resivore for the pilot side master. Pushing on the copilot pedals will go through the pilot master cylinders to actuate the brakes. I like the Resivores on the right side because it puts the harder brake pedal on the pilots side. I write confusing. I need th draw a picture.

I found a diagram. I would put the resivores on the right side. this setup will have slightly softer pedals on the pilot side.

http://static.veracart.com/matco/item_p ... ument1.pdf

What is the most common routing pathway for the brake lines out of the cockpit going to the wheels?
I can find only one reference in NL 19 pg 78 suggesting going out through the 3/4" angles about 2 inches back from the firewall. That seems reasonable but I was interested to know if there have been any other suggestions since 1966!

The NL 19 suggestion is how I have now run my brake lines. Previously they went through the firewall and then down the gear legs. I was using the Nylon II 1/4" tubing, but have switched to plastic covered braided lines from Bonaco.

I'll have to look , but I believe I went thru the floor just inside the angle so the line would run thru the gear leg fairing down to the caliper. Do not use nylon line. Use the SS braided brake line and fittings. I put a rubber grommet in the floor to run the SS line thru. The SS line is not that expensive, but like everthing else the fittings are the majority of the cost. I got the line and fittings from JEGS.

RB

On my aircraft I have -3 stainless braided hose from the brake cylinders to an AN bulkhead elbow through the firewall, the elbow is on the engine side. From the elbow it is 3/16 stainless tube down each gear leg (I think it is stainless). At some point in the gear fairing it changes to a hose to the caliper.

_________________
Bruce Finney
N18JF T-18C #262
Yelm, WA USA

Going out through the firewall would be good if you were wanting a removable floor but if you were leaving the floor fixed does it offer some other advantages?
I had planned to use AN -3 (3.17mm 1/8") PTFE Core (Teflon) Stainless Steel (304) Braided Hose throughout, It seems like a good gear.
Temperature range from; -73 deg Centigrade to +232 deg Centigrade
Maximum Operating Pressure (psi):
3,000 psi Burst Pressure Min (psi): 12,000 psi
Bend Radius Min (in) 1.5

I think if you wanted a removable floor you could still do a cut out with a doubler that would allow the line to pass thru and then slide out when the floor was removed. The reason I went with (1) line from the brake cylinder to the caliper was to do away with extra fittings and solid brake line. Good hose choice. Doubt you will reach any of the line limits in this lifetime or the next !

RB

I used a rubber hydraulic hose to go through the floor, just a 3in piece, it fits in the hole very tight and the hose is permiated with a steel brade. This piece of hose does not move, I ran the Nyloseal nylon hose right through this Hyd hose that I put thought the floor and the fit is snug. No cost for fittings, nothing complicated and very simple. The Rubber Hyd hose goes through the floor and straps to the gear leg and shoots the Nylon hose right nice and tight to the gear leg down through two more pieces of Hyd hose that are strapped to the gear leg and then on down to the caliper.I have brakes on both sides, pilot side and copilot side. The copilot side is slaved off of the pilot side, masters on pilot side and the schematic for this setup is in the Aircraft Spruce catalogue. it is simple ,light, not a lot of cost but it is effective and trustworthy.........