BVM brakes locked up ??
 

Ive seen this a few times over the years, usually as I recall it is one wheel or the other but not both. In my case to both wheels stay locked up (brakes on) even after bleeding off all the air pressure and with the brake valve in the off position. after 30 seconds or so with all pressure bled off the air tank the brakes finally released. I pumped it back up and they were again locked up without even applying any brake valve (UP 6). I once again let all the pressure out of the tank and after thirty seconds and a few applications of the brake valve on and off they released ? does anybody have a good idea whats happening and how to prevent it ? This all happened after the first flight this morning where they worked completely normally and they worked propery three flights last weekend.

RE: BVM brakes locked up ??
 

My suspicion here is not your brake valve but your brake assembly at the rim. If you have the o ring type as the ones that come with the Faibao rims, these may be sticking.
I would be checking that nothing is sticking at the brake assembly at the rim.

RE: BVM brakes locked up ??
 

I don't think it is the valve either. I think it is the brakes that are either sticking or somehow trapping pressure. I haven't had a chance to go look at them yet. I will in the next few hours however.

RE: BVM brakes locked up ??
 

Hate to disagree but I really don't think there will be a problem with the wheel brakes. I've been using BVM brakes for 12 years now and I have never ever had one fail. I'm sure it will be something to do with the U.P valve.

Jason

RE: BVM brakes locked up ??
 

I totally agree with Jason on this one. +1

RE: BVM brakes locked up ??
 

You may be right and the fact that both of them locked or more correctly stayed locked up after taxiing back to the pits and stopping at the end of flight number one does tend to make one think that for both to stay locked maybe it is a valve issue.

On the other hand I have had this happen more than a few times over the last 20 years of flying BVM stuff and its happened with several different type of brake valves or actuators sometimes both brakes stay applied and most times it seems like only one stays applied.

It will be interesting to see if I can get it to lock up in the workshop. I guess Im hoping I can so I can then figure out the source of the problem.

RE: BVM brakes locked up ??
 

Guys please correct me if I'm wrong, but if he has tryed it with a BVM brake valve and ultra precision valve with same result could it then be that the brake assembly is faulty.

RE: BVM brakes locked up ??
 

I have not flown this particular airplane with anything but the UP 6 valve. All in all I have had very good luck with these valves over the years. Till possibly now that is.

RE: BVM brakes locked up ??
 

My misunderstanding and I agree they are good valves

RE: BVM brakes locked up ??
 

If the brakes lock without applying them but while pumping up the tank seems like it is the valve.

RE: BVM brakes locked up ??
 

Everything needs maintenance once in a while. Just rebuild them. Sometimes just taking it apart, cleaning the rims, o-rings, valves & plungers is all it takes. I've done it a few times without having to buy or replace parts. Also, if you haven't used the plane in a long time, that could be the reason.

RE: BVM brakes locked up ??
 

Well it turns out we were all wrong. I have a bad servo. It will only work in the direction of brakes ON, but will not return to the brakes off position except when rotated by hand. Then the next time brakes are applied they go on and stay on. Appolgies to BVM and to Ultra Precision Valves. The bad news is it takes quite a bit of disassembly and unbundling of servo cables. Had to remove the engine the bypass and one fuel tank as the wires run in an otherwise impossible to access area under the bypass and fuel tank.

Having solved this problem I am on to my next issue. Watch for my post regarding tip stall and how to mitigate or lessen the severity of tip stall on this particular airplane.

RE: BVM brakes locked up ??
 

Hi,

I've had BVM brakes lock up plenty of times. No biggie at all. In my case, it was a matter of lubing the ring with the right grease; and in one case, it was the steel pin seizing up on the brass bushing in the wheel hub. I took a dremel and polishing compound to the axel and used that expensive white grease there, too. Problem solved. I guess in this case, it was a servo, but yes, the BV wheels/brakes do lock up if not properly lubed.