SonexBuilders.net

After 16 hours of test time on my ONEX, I've found the machined drum shoe type brakes vibrate very badly and have poor braking ability. So, I have ordered the Sonex disc hydraulic brakes hoping to cure this problem.
Anyone with any experience with these on a ONEX, please chime in.
I'm out of state now hoping they will be at home when I get back.
Hopefully these will be as good as advertised. Maybe I should have
Inquired with some of you prior to ordering.
I tend to trust Sonex since they designed the plane.
Want to comment here, Kerry?
Frank
ONEX 090

I have a Sonex and not a Onex, but I switched from the machined mechanical brakes to the Sonex hydraulics and have been very happy with them. Smooth even braking, and I can hold the plane in place during a full throttle run-up.

The vibration problem with my brakes was not the drums, but the Azusa wheels. They are not machined accurately so the wheel wobbles and the brake drum wobbles with it. It's pretty easy to check. I ran mine with fairly loose bearings for some time, which helped, but eventually re-bored the wheels to take a 3/4" ball-bearing with a slightly larger OD than the original bearing. Did the boring in a lathe with the wheel rim held in the 3-jaw chuck. I also run a spacer between the bearings so that the wheel nut can be fully tightened. Now the wheels run true, the pressed steel brake drums run true and the brakes work well.

Peter Anson
Sonex 894
210 hours

Peter's comment on wheel bearings reminds me that the bearing seats are often not fully pressed into place on those wheels, and will shift which can them not to run true or wobble. Seats can be pressed in with 1/2" bolt or threaded rod running through large sockets or stack of washers that closely fit bores to press on OD of seats. Do not press with the roller bearings in place, just the seats, and do not use a hydraulic press unless supporting the wheel hub, not the rim.

David A. Sonex TD #1327

Today was the first day that I had my Sonex fully assembled and was running around the airport with it to see that the engine stayed cool. I took it to the runway twice. First time at about 40 mph ground speed it started a vibration that was next to violent. Second time was the same but I pulled power before it really started hopping. Due to it starting about 35 and being smooth up to then I assumed that it is wheel balance .

Any thoughts on this?

Regards, Ed

Not sure about the vibration issue (maybe bearings aren't seated or the nut isn't tight) but you should be carefull doing runs down the runway at 35 to 40 mph. That is about the speed that the plane wants to start lifting off. I can usually pull it up into ground effect flight at around 40mph from the 3 point stance. Dont' get caught off guard if suddenly you are flying before your plane is done and ready to fly.

Keith

Ed,

I haven't noticed any problems with wheel balance on mine; maybe someone more experienced with that will chime in.

Check the things Keith recommends.

I would also double check that the legs are tight--can you jack the airplane and find any looseness in the legs by hand? Are you sure the toe-in is correct? If you position yourself far enough in front of the airplane along the centerline of the airplane, I think you might be able to eyeball it enough to tell that at least they both have the same amount of toe-in. My brakes were attached to the axle a little loose which allowed them to rotate slightly and rub on the drum--this could cause a hard to troubleshoot vibration. Do you have anything like that going on?

A camera mounted under the fuselage might help you figure out what is happening.

I also agree you should be careful doing runs at that speed. I didn't go faster than 25 before my first flight.

Balance shouldn't be that big an issue that the gear leg would shake violently. I'm be looking extremely close at the toe in on the axles. This almost sounds like toe out. Wouldn't hurt to give it a good check.

Larry
Waiex 121YX

My first taxi tests I had a violent shake as I approached take off speed. It turned out to be the toe in was way off on both axles. I think I may have reversed the gear legs after I drilled them. Drilled new holes in the axle attach fitting and welded a reinforcing plate.

I would guess toe out except I was very careful on initial install to get the toe in set right. Also everything is smooth until I was close to flying speed and then it gets to vibrating quickly. I am going to check the balance. On another topic, I think it was landing gear shimmy, some say it was cured with ceramic beads. I don't know about that I'll use stick on weights. It will be a week and I will post results.