twinman

My Feedback: (2)

Installation of Brakes on VQ P-38-1

My field is a 500-foot long landing strip of concrete. The problem I am running into is that I tend to land a P-38 fast to maintain maximum control. (The fact it is slightly over powered does not help) Due to the fast landing speed it tends to run off the runway, which can damage the struts. The structure is ok, but has bent the struts.
Various ideas were passed around and suggested by my “BUDDIES� at the field.
Suggestions included,� Hover it in�, “Cut the power up high�, “Helicopter landing�, and my favorite was “JUST RETRACT THE GEAR, that will stop it on the pavement!!� Usually that one was followed by “Wait until I get the video camera!�
Now, to maintain some bit of relationship with my fellow RC pilots, I will just say that I rejected……ALL OF THESE IDEAS!!!!! My friends are nuts!!!!!!

Ok, on to the story. I decided to install pneumatic brakes on the main gear of the P-38.
A quick call to Spring Air, http://www.retracts.com/, and the brakes were on the way.
Naturally, the story does not end there, or the expense!!
I wanted to avoid skidding the expensive tires down the runway, so the normal off-on valve was rejected. I have used the Ultra Precision, http://www.up-1.com/ , variable pressure regulator UP 6 brake control valve in the past and been very happy with the results.
Yes, there are other manufacturers of this type of valve, but I tend to stay where I feel safe from past experience. The idea is that I can apply the brakes in a controlled manner as I land…….how?? Later!!! Keep your pants on!! ( Retract the landing gear!!! Indeed!!)
The other neat part is to taxi to the runway, on to the strip, set up for take off, set the brakes, and run the engines up!!!!!! Then blast off!! OK, with over size engines, maybe I will only go part way up!!! ( Will still be cool!!)

More Stuff to Buy

What did you think you would get by with only the brake kit and special valve…….no way nitro breath!!!!
The brakes are designed for only one type of wheel. Now off to the local hobby store for Robart Low bounce scale 3� part number 114 wheel and tire assemblies.
Through yet?,,,,,no. As you go through the instructions, you find that you must buy inserts for the tires from Robart to allow these tires to work with such a heavy plane. The Robart part number is #FOAM3. Do you think the local hobby store or his wholesaler stocks this?…….not!! Call to Robart and it is on the way. Secret……Is nothing more than hard foam solid tube .75� in diameter..
Now more air tubing, three more air tees and one quick disconnect, for the air tubing.
Threaded rod and clevis to connect the servo to the brake valve.
Now one mini servo and wiring tee and you are all set!!!

Told you twins make you crazy!! I will be posting addition pictures and my poor ideas about this installation.

twinman

My Feedback: (2)

Foam Installation into the tires-2
The first thing you do is unscrew the center hubs of the existing wheels. There are there screws that can be reached from the outside via the “Spokes�. Cut the foam inserts to the required length and max length to strengthen the rubber tires for the weight. After unscrewing the original plastic hubs and leaving the outer “Spoke Wheel� half in place, you must insert the foam inserts into the wheels and cut to maximum allowable length.
15,14,13

twinman

My Feedback: (2)

Original Hub Enlargement-3
Drill out he original holes to insert the new brake drum screws. I used 3/32 drill.
7

twinman

My Feedback: (2)

Brake Installation to the Wheels4

The new brake hubs have the exact bolt pattern of the outside plastic hub and furnished screws for the hub. Note, you need to enlarge the holes of the plastic hub to get the new screw in easier. And loctite the new screws in place. Look into the hub and you will find the new screws going into the hub a bit. They must be flush to allow the brake hub to go inside. Out comes the cut off tool and grinder, and the problem is solved. Be careful, the brake drum is plastic.

9,10,12

twinman

My Feedback: (2)

Hub Installation-5
The hubs have their own bushings that must be lightly greased to reduce wear.
The manufacturer also recommends to lightly coat the inside of the brake hub with Vaseline to reduce pad wear. I would think this will increase the air pressure required to hold and stop the plane, but I did not design it.
8

twinman

My Feedback: (2)

Brake Back Plate Modification
You must test fit the back plate to the strut. You will note that the back plate is stepped to allow grinding to get the back plate up to the strut. Do not take off too much, but make sure the back plate is tight against the strut.
6,3

twinman

My Feedback: (2)

Brake and Wheel Installation
I measured and found that the axle had to be shortened, so it was cut off to keep the axle and keeper inside the “Spokes�. I used the self locking push on cap type lock for the wheel, after cutting small grooves in the axle to make sure it locked.
Make sure that you lubricated the bushing in the brake drum before installation.
1,2,3,5

twinman

My Feedback: (2)

Air Line Installation
Connect air tubing to the air barb on the brake hub, lightly tie to the strut and make sure it will not bind during retract operation. Run to the center of the wing and out of each side. Connect the two lines with a tee, and connect the tee's line to a quick disconnect so that the center pod can be removed for servicing. Note, make sure that the male and female are different for the retracts and the brakes, or it WILL happen that you will reverse the lines during maintenance!!!
Put another tee into the air line going to the air tank from the fill valve. Note, the brakes take a very small amount of air, so I see not problem with the existing size air tank.
Run the pressure line from the air tank to the proper inlet of the control valve. Run the outlet of the control valve to the other male or female quick disconnect for the wing connection to the main brakes.

twinman

My Feedback: (2)

Electrical and Servo Connection
Now the fun part.

I used a mini servo and set the linkage to the innermost hole on a short control arm. The servo must be y’d into the elevator servo’s wiring and must be the proper direction of travel to actuate the control valve during “down� elevator operation.
The theory of this installation, and operation, is to use “Down� elevator command to actuate the brakes proportionally. The more down elevator commanded, the more brake pressure. In flight, most pilots of a scale P-38 would not use the down elevator command much or at all. This means that, while the brake servo is moving, very little power, or air, is consumed as the brake control valve spool has no restriction to movement and does not send air as the spool is moved out, only in, and you must set up the linkage to accomplish this. I also set the linkage travel so that brakes are only beginning to be applied at 25% or more down elevator. (Just in case I needed one of those gentle outside loops.)
I installed the extra mini servo beside the nose wheel servo and ran the linkage to the control valve, after drilling a small hole in the bulkhead for the push rod. The control valve was mounted beside the air tank. Now the travel and linkage is adjusted as described above. Yes, you are seeing three servos in the lower center pod!
Put all this wiring and air tubing back into the top and bottom of the center pod and check for operation. Yes, you now have 13 servos in this plane. Told you twins make you crazy!!
Take Off
Taxi the plane to the field and be cool, don’t let you buddies know about the brakes. Line up for take off, command down elevator to set the brakes and run the engines up. Don’t watch their faces…..you are concentrating on taking off the coolest plane at the field. Let the elevator go to neutral and the plane takes off down the runway like a shot.
Landing
Do the normal “Pilot Stuff� for approach and landing. ( Ignore the normal hoots about you running off the runway!!) Land, and go to down elevator gently the first time to stop the plane. Too much brakes and you will skid the expensive tires. Watch out for any signs of one brake holding more than the other…just in case. If problem here, relax the down elevator and stop…….before the end of the runway. Now taxi back, stop, and kill the engines.
Try to look like it was just another day at the rcfield…….flying the Lockheed Lightning P-38!!!!!

14.15.18

CafeenMan

OK, this is all very interesting, but you never said how well they actually work. Was it worth the expense and do they solve the problem you originally purchase them for?

Forgues Research

My Feedback: (7)

If ever you build a bigger airplane, look at these brakes.

brakes

Roger

twinman

My Feedback: (2)

aerografixs
"If ever you build a bigger airplane, look at these brakes." Now that is a set of brakes!! The P-38 in the picture beside my name has 5.5" main gear wheels.

As for the test of the concept and trouble and expense......depends upon weather tomorrow. I did this installation on over powered Yellow Aircraft P-38, in the past, and really did like it.
I installed the brakes after seeing a P-38, at Bomber field, taxi back after landing, with engines running and two guys went out to stop it from coming into the pit area.......Ordered brakes next day!!!
Will keep you posted.
twinman

grbaker

My Feedback: (29)

I have used these brakes on several ducted fan planes and they worked very well on grass or pavement. The bad thing about them, is that once you've used them, you'll want to put them on all your planes.

twinman

My Feedback: (2)

grbaker
Is this one of those things that you really never add up the cost.....only the cool factor????
Let's see 108" P-38, 120" Fokker F27.......uh later,,,,,,got to go update christmas list!!!
Rats,,,,,,,Fokker has dual main wheels??????
Twinman

egor

Pretty cool Twinman thought about doing this on mine just on the main's

egor

danmilo

My Feedback: (4)

Thanks Twinman!


Dan

roadtrip

[quote]ORIGINAL: twinman

Note, the brakes take a very small amount of air, so I see not problem with the existing size air tank.

Any problems with air supply for the retracts while running the brakes off the same tank?

twinman

My Feedback: (2)

I used the same system on a Yellow Aircraft P-38 and no problems if set up as above. Makes life simpler.
Twinman

roadtrip

Twinman,

After inserting the foam tubes, I found that using 4-40x3/8 socket head screws work better, as some of the button head screws that come with the brakes were rounded out while trying to screw them in and I couldn't get them back out again. I used my dremel and a fiber wheel to groove a slot in them and backed them out. The 4-40 screws fit perfectly and are easier to work with. Also, they don't protrude out the other side. It must be because I didn't try to press the wheel halves together as I screwed them in, causing the heads to round out. What do you think?

KevinM

Hey Twinman,

As has already been noted, I'm also sure you'll find the brakes very addictive. If you find over time that the Robart wheels don't hold up very well on your concrete runway, however, there are in fact a plethora of alternatives. Most of the "made for" brake sets have wheels made of solid hard rubber so they stand up to use on pavement much better. If you shop around, you can actually find complete sets for about the same as what you likely paid for your setup. (Check out the link from my tag-line.)

Also, if I may add a quick air-saving suggestion for setup: For guys using air-up/air-down gear (non-Spring air) you can connect the brakes into the "gear down" air line instead of the tank supply line, that way no air is consumed when the gear is retracted regardless of brake valve setup. Another way to conserve air while flying if you have an extra channel is to use a mix to drive the brake servo, where the mix is turned on by your retract switch.

twinman

My Feedback: (2)

KevinM
We are soooo unworthy!!!! Fantastic ideas.
Thanks,
Twinman
PS roadtrip Yes, I had to hold the wheel together to install the screws. Another modeler says to use the spray foam for the inserts. Might have been cheaper. He says to drill two small holes for inlet and outlet.

roadtrip

T/M, I'm finally finishing up my P-38 and getting the brakes installed from the same air tank as the retracts. I see in your photo of the brake valve, that there is what looks like a fuel filter connected from the filler valve. What is that for? And is your quick disconnect running from the brake valve and a tee off of the nose wheel line? I'm still trying to figure out where the hose from the bottom of the brake valve goes, as well. (Maybe I need to put this thing away for a few days and check to see if the sun is up or is it the moon?) The wife is in Italy visiting parent's and I'm taking advantage of the free time!!!

twinman

My Feedback: (2)

roadtrip
I am not sure what brake valve you have. The quick disconnects are from the bottom pod to the main retracts and the brakes on the main retracts. This allows me to remove the center pod for maintenance. I originally used the main supply line to the tank to power the brake valve, but one of the guys here at rcu came up with the idea to tee in on the line to the "down" on the retracts. Less chance of a leak. I like it. The "Filter" looking thing is a one way check valve between the filler valve and the tank. My filler valve did not have a check valve.
Other than the war,(Roadtrip is serving this country overseas) is it getting warmer there and about ready to fly?
Twinman

roadtrip

Im using the same brake valve you have. Which line would be the"down" on the retracts? I have the Spring Air 702 system which has a nipple on the bottom of the valve and one on the side. As far as the weather goes, today was the warmest this winter and hopefully with spring around the corner, I'll be ready.

twinman

My Feedback: (2)

Opps, thinking of the two way retracts... Opps brain is going. The outlet line closest to the opposite end of the valve from the spool, is the outlet. You cannot test it by blowing. It works by a differential Must be hooked up to function.
Twinman