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Robostruts

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Old 07-26-2014, 02:38 PM
  #1
jszeiter
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Default Robostruts

Repeated failure is making me desperate folks. Someone, anyone, please help me!

I have attempted on multiple occasions to mount robostruts to eflite electric retracts. Each time - failure. I have bought steel dowel pins from McMaster Carr that are incredibly hard, and seem perfect for the job of fitting into the eflite retract, and also into the robostrut. I then drill and tap, very carefully (I've tried both 3mm and 4mm size grub screws). I then use my dremel cut off wheel to file a flat spot to receive all grub screws.

Every time, the same thing: I tighten the grub screws, test the security of the strut (eg. not pivoting), get unhappy because I can move it, tighten it some more, then finally strip out the hole I just tapped.

And now, I've taken to reaching for the JB Weld to just glue the @*&#mn thing in there (knowing that in the event the pin breaks, I've just blown a whole strut...)

ANY ADVICE would be much appreciated. IN short: how does one successfully mount robostruts to eflite retracts using pins, and grub screws?



Thanks guys.
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Old 07-26-2014, 07:29 PM
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mustangman177
 
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I've used the robostruts in the past and know the frustration-anxiety you're talking about. Been several years back though.

Are there not 2 set screws to secure for each leg ? Believe I used blue lock tite to set the screws as well. Also I drilled out the original hole to the next larger set screw. Still had to re-tighten after several flights.

Hope this helps
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Old 07-27-2014, 11:44 AM
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Calvinman
 
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Hi JSZeiter.


I don't really know anything about robo struts, but when mounting a collar to a shaft having two set screws 90 degrees apart help keep it in place. If you can dimple the shaft by using a dirll bit just small enough not to remove the threads will also help. Also as Mustangman mentioned loctite can't hurt. If you can heat the struts for removal you can also use permanent loctite and bearing mount loctite on the shaft itself.

Calvi

Last edited by Calvinman; 07-27-2014 at 11:45 AM. Reason: one word too manny
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Old 08-03-2014, 07:14 AM
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DavidAgar
 
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I just file flat spots on the gear and use Loctite on the set screws and mine have not been an issue. I do check them prior to each flight, but I have not had any issue's with them coming loose. Good Luck, Dave
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Old 08-04-2014, 05:51 AM
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If I understand your problem correctly, it sounds like you are collapsing the strut tube when you tighten the set screws. If that's the case you need a support piece inside the upper end of the strut (above the compression spring) to prevent the strut tube from collapsing. I use a 1/2" long piece of steel rod, sized to the strut tube ID so the tube does not collapse. Robart provides a nylon plug for this purpose but I prefer the steel plug.
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