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-   -   Love My Robart Retracts; Hate My Robart Retract Problems: (https://www.rcuniverse.com/forum/rc-warbirds-warplanes-200/11613621-love-my-robart-retracts%3B-hate-my-robart-retract-problems.html)

Electriceddie 02-20-2015 03:09 PM

Love My Robart Retracts; Hate My Robart Retract Problems:
 
7 Attachment(s)
Hi Guys,

I have an issue with the 630 Robarts Retracts.

The mounting blocks appear to be level and OK. But when I lay the retract into the mounting blocks it seems to fit on the mounting blocks fine. The problem is when I screw down the 4 screws in each corner the retract becomes very stiff when I try to operate the retract up & down. As soon as I loosen 2 or 3 screws about of a turn or so, then the retract works fine.

The retract works fine when out of the plane. The other retract works fine in or out of the plane. The mounting blocks in both wing halves look the same and so I am not sure what is the issue. If I had to guess, I think that somewhere along the line that the retract is getting pressure on the flanges which in turn is causing a slight binding action on the retract when the screws are tightened down. (Look at the one Pic of the silver part of the retract that looks like it has some wear on it)

The mounting blocks are flat piece of 2 layers of plywood, making it almost a thick. When I say tightened down, I really mean the screws are just barely snugged down. I included some pics to see as well. I noticed that there is one pic in particular that seems to show some wear on the silver part that goes up and into the retract between the mounting flanges of the retract.

Also you will see the piece of Pine board with the U - shape cut out in it, this was a test board that I mounted the retract that was giving me the issue and it worked fine.

Has anyone encountered this before? Let me know what you guys think?

Thanks
Ed

RBean 02-20-2015 04:59 PM

Electric Eddie, I have found that Robart retracts are very susceptible to problems from being slightly twisted. I used glass bedding compound to create a perfect match between the Robarts and the mounting rails. Use plenty of release agent on the retracts, us tape to keep the compound from flowing into the retract let dry overnight. Remove retracts and trim off excess. I the retracts did worked ok after that. A PITA but worked.

CK1 02-20-2015 05:24 PM

The landing gear mounting rails in the wing are probably not truly parallel to each other and tightening the gear down to the rails forces a twist in the gear and creates a bind.
When tightening the screws down tighten one at a time , checking operation after each bolt is tightened to determine where the low or high rail is ans then shim as needed with washers to prevent binding

Electriceddie 02-21-2015 11:38 AM

Using Washers Causes a Slight Gap But Works ,But are There Issues?
 

Originally Posted by RBean (Post 11987374)
Electric Eddie, I have found that Robart retracts are very susceptible to problems from being slightly twisted. I used glass bedding compound to create a perfect match between the Robarts and the mounting rails. Use plenty of release agent on the retracts, us tape to keep the compound from flowing into the retract let dry overnight. Remove retracts and trim off excess. I the retracts did worked ok after that. A PITA but worked.








Hi Guys,

I tried using a couple of washers here and there under different screws combined with tightening and loosening the screws in different order I was able to get the retract to work pretty well.


I am using the one retract that is not mounted sitting on the bench as a comparison retract to the one in the wing giving me trouble and I almost have a match. If the retract is deployed and I slowly raise the wing by the tip and stand the wing half on the root the retract folds up into the wing on its on weight. I would presume this is what our desired goal is, to get the retract to close smooth like without any binding or stiffness?


If that sounds good, then is it OK to go with using washers under a few of the screws to get the retract mounted correctly instead of using the epoxy method? Now my other thought is with the washers now, there a slight gap under the flange from one screw end to the other screw end.

Are there any issues foreseen by using washers which will cause a slight gap that may cause some loosening or vibration?

I as using one inch socket head sheet metal screws with washers and lock washers. But at completion I will use Locktite as well.


Thanks a Bunch

Ed :cool:

Greg Wright 02-21-2015 01:55 PM

The issues that i see happening are. The washers will start to get embedded into the wood and you will have to keep retightening the screws or bolts and after a while the issues will just end up returning. What i would suggest is you try to get the gear to work smooth with either just the front or rear screws tightened and then make a shim out of good quality plywood to fill the gap on the other mount to support the mounting flange on that side of the gear.

prop wash 02-21-2015 03:33 PM

Check to see if one or more of the flanges is true.Look from the front or rear and see if there is one bent more than the other.Tom

chistech 02-21-2015 05:16 PM

leave your washers in and bed the retract with the filler like was suggested. Then the retract will sit on both the washers and epoxy bed. I use vaseline on the retract rails to keep the retract from sticking. If you think Robarts are bad, try the new electric retracts. They're worse.

Eddie P 02-22-2015 12:24 PM

With as many issues I've had with air leaks becasue of where I live (high mountains, hot and cold temp swings, dry air) I still happen to prefer the latest round of electric retracts, especially since the actuator motors have been improved int he last couple seasons.

Retracts have always been a PITA. Pick your poison - dried out seals and leaks, valves going bad, retract servos and linkages, miles of tubing and overhauling seals and tubes, or retract motor issues that happen more and more rarely these days (to me at least, beel e gearing for many seasons now). To me I still prefer a careful installation of electric retracts these days. The untrue mounting rails and installation shims would have been necessary on a pneumatic retract too but it might have just shown up in flight with a gear up landing as a result vs an obvious issue on the bench.

Electriceddie 02-22-2015 02:47 PM


Originally Posted by Eddie P (Post 11988490)
With as many issues I've had with air leaks because of where I live (high mountains, hot and cold temp swings, dry air) I still happen to prefer the latest round of electric retracts, especially since the actuator motors have been improved int he last couple seasons.

Retracts have always been a PITA. Pick your poison - dried out seals and leaks, valves going bad, retract servos and linkages, miles of tubing and overhauling seals and tubes, or retract motor issues that happen more and more rarely these days (to me at least, beel e gearing for many seasons now). To me I still prefer a careful installation of electric retracts these days.


The untrue mounting rails and installation shims would have been necessary on a pneumatic retract too but it might have just shown up in flight with a gear up landing as a result vs an obvious issue on the bench.





Hi Guys,

I definitely agree with you with your last sentence..............


I have an idea based on some of the advice here. I have a boat and in the marine stores of which I a very familiar with , they have a product which is an epoxy based product however it's form is like clay. There are two rolls of material, one gray and one white. You cut equal parts, say about an inch of each and roll it and message it together until it is totally mixed. This can then be used to do with what ever you would do with say the epoxy and micro balloon mix. I know they sell a product like this in the big home store etc.

What do you think of using this for bedding the retracts?


Thanks again guys for all of the advice

Ed


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