Dynon Roll Servo fit bad

I posted this on the Dynon Forum as well.

I started the install of the roll servo on my RV-8A today and after taking the lower bell crank bracket off to install the Dynon bracket I discovered the holes are off. The hole that the bell crank bushing bolt goes through should be in the middle of the two holes that attach the bracket to the wing spar. My bracket is off just slightly. I can put it all to together just fine, but if left this way the bell crank bushing will start to ware unevenly and develop some slop. I wonder if I am an isolated case or if others might have this issue. It would be easy to miss, you might end up with the bell crank bushing waring out prematurely after a few hundred hours.

The linked picture shows what I mean. I bolted the two brackets together through the bell crank bushing bolt hole. I then set it on graph paper with the center axis of the stock bracket highlighted in orange. You can see the miss alignment, I confirmed this by holding the Dynon bracket up to the full size bell crank drawing on DWG 15A (top view). The holes that attach the bracket to the spar are fine, it is the bell crank bushing bolt hole that is not centered between the spar attach holes.

http://www.mykitlog.com/users/display_log.php?user=rvg8tor&project=403&category=0&log=79571&row=1

I am posting this so others might check their brackets as well, I bought mine a few months ago so maybe mine is an isolated one. Anyone else have this issue. I am snake bit today, first I found one of my fuel senders is bad and now this

I received and installed a Dynon roll servo about a month ago. I did not notice any fit problems. I was actually impressed with the quality and cleverness of the installation kit.

Luis Luciani
RV8

I almost miss it

Luis,

If I had not compared the two I too would have installed it as is. It is not very noticeable once installed but just me if yours was like mine your bushing bolt is no longer perfectly aligned. I want to have Dynon send me a replacement. If that too is the same then I may have another issue, I am almost certain it is the bracket since I can see the mis-alignment when compared to the full size DWG.

Mike,

I'm guessing you received a bad part. I believe those are the same brackets used on all the RV's and even the beta parts I received fit like a glove. Give Dynon a call today, they should have no problem replacing it.

New one on the way

As expected Dynon was very responsive to my situation. The new bracket is on the way. I will send back the one I have. I did some more measurements and the bushing hole is off in the inboard outboard axis by 1/16", the fore aft alignment seems OK. I also compared the diagrams that Dynon sent in the instructions. Measuring from the diagram the bushing hole should align exactly between the two spar attach holes. My bracket has the hole 1/16" too far inboard. Now I am not certain being off 1/16" would create that much of a problem in the bell crank bushing, but I want to try and fix it if a new part does the trick. Sometimes I think I look too closely at this stuff, if I had not compared mine to the original I would have installed the thing and flown for years with no problem in all likely hood.

Follow up with new bracket

Amazing, I received my new bracket from Dynon this morning and I only talked with them yesterday, UPS Saturday delivery, more service than I expected.

The new bracket and the old are the same, just slightly off. This tells me that all of the brackets have the same issue. I guess it is not an issue yet since all of the testers have been flying with the Dynon bracket. If it becomes an issue it will show after several hundred hours if at all.

I think the play between the bell crank; the bushing and the bolt will allow for the 1/16" the bushing hole is off. I added some more pictures to my log (link to entry below) to show what I am seeing, trust me I measured this several ways and come up with the same thing.

I am curious, if someone else has the roll servo bracket for an RV-7 or 8 (they should be the same) compare it to DWG 15A and tell me if you don't see the same difference.

http://www.mykitlog.com/users/display_log.php?user=rvg8tor&project=403&category=0&log=79702&row=1

I installed one about 6 mos. ago or so and I don't remember any problems. I'll go double check mine as I still haven't closed my wings yet.

Rick Maury
RV-7 SB
Tail and wings done, Fuse at 50%

No install problem

Maury said:

I installed one about 6 mos. ago or so and I don't remember any problems. I'll go double check mine as I still haven't closed my wings yet.

Rick Maury
RV-7 SB
Tail and wings done, Fuse at 50%

Click to expand...

Rick,

You would not have had a problem on the install, the bracket goes in just fine, I just happen to notice the holes in the Dynon bracket did not perfectly align with my Van's bracket. This made me look more closely and compare things to the full size DWG. At this point since many are flying with this bracket I don't think it causes problems initially. There is a lot of play in this area so that helps the very slight misalignment no be an issue.

Let me know what you find with yours.

Bad part?-my guess

Rick,

These parts are punched or CNC'd. Is it possible something happened during the manufacturing? Sure.

I received my RV-7 high pressure fuel pump kit from Van's. The mounting plate didn't fit between the floor stiffeners. Several other builders had this problem as well. The accepted solution, cut the plate and rivet it back together. My solution, call Van's and investigate.

Upon calling Van's builder's assistance and having them check their inventory they told the parts I had were good and I must have messed up. However I explained to them that all the parts that control the spacing of the floor stiffeners are prepunched so I couldn't have changed a thing. I requested they go back to the engineering and verify the bracket dimensions. I received a call back and they said they had a bad batch of parts and they were pulling the inventory and having them remade. How long this incorrect part was delivered to customers is unknown, however an incorrect part is still incorrect.

The moral of my story is even though a part maybe made by computer, it still can be made incorrectly. It maybe that a second batch of parts were made after the "tester" batch and you got the first lemon. Have Dynon check their engineering against the parts. If they can't find the problem they should contact Van's for an actual measurement.

Here is another funny CNC story. I have a part laser cut for the DRDT-2. It is a simple rectangular flat plate with 4 holes and 4 corner radii. The laser cutter had made these parts for a year or so (several batches of 100 or more). I increased the corner radius and sent them new files (drawings) to work with. This is a very minor change to the programming of the CNC laser cutter. I got the parts in and started to assemble. The parts were 2/3 size of the original parts. I called the laser cutter and asked what the #$@$##$% was going on. How could this have happened. It turns out that I changed the drawing scale of the electronic drawing and they used it for there direct programing and didn't check the dimension or scale on the print. They proceeded to make new parts and now every time I send in an order the include a note to "check dimensions". A Very simple part, proven technology, still can be messed up.

Food for thought.

Bad CNC punch

I ordered my original mounting set back in October, and the bracket I just received is a perfect match to the old one. I think that what ever Dynon used to make their prototype bracket is just off a bit from what the stock bracket is. I did notice that it pushed the bell crank inboard a bit when I finally installed the bracket. I have the rigging template (W715 I think) in the wing and the inboard end just touched the lip of the spar doubler, the rigging template is to lay flat on the spar. After installing the Dynon roll mount I had to trim a slight bit of the template so it would not sit on he spar doubler. This confirms what I found with the bracket, it puts the bottom of the bell crank bushing hole inboard by 1/16". The bell crank moves nice and smoothly with no binding but the bell crank bushing bolt is no longer perfectly vertical.

If you have been flying a while with the Dynon roll bracket in the wing I would be curious if there is any asymmetrical wear in the bell crank bushing? Something to check during an annual perhaps.

Mike,
I just took mine apart and it is exactly the same as yours. I purchased mine last Oct. '08. I don't have any control surfaces hooked up to it yet, but there doesn't appear to be any binding; so I don't think there will be a problem.

Rick Maury
RV 7 SB

Will meet Dynon

Since I live a little over an hour away, I plan to go visit Dynon in person. I have already made contact and they are going to try and arrange the meeting with the engineer for this project. I will take my stock bracket and pictures and Van's DWG.

I have to say again what a good company Dynon is, there response to this issue is commendable, since there are no reported problems with the currently flying brackets they are still interested in , what I have to say, and I am sure will take action to correct any minor dimensional issues if warranted. As I have said before there most likely will be no issues with the current brackets flying, however refining the fit of the bracket to match the stock bracket I think is a good thing.

Cheers