DEPS (was RE: MK Dual Elavator)

[Ken Blackwell]

On my first attempt at the .070" CF pushrod system, I bought the CST kit with the teflon sleeve/tubes. After fooling with them for a while, I pitched them in the trash can and went to the Dubro nylon antenna tubes. It is almost impossible...at least for me...to get them attached to a spar without binding. So here is a vote ABSOLUTELY against the flakey/flimsey teflon.

For my next airplane, I'm going to use CF tubes with the CF pushrod and NO balsa supports/ladder. I understand the weight is about the same.

Evreryone has their own way....smile.

Ken B.
  ----- Original Message ----- 
  From: Scott Smith 
  To: discussion at nsrca.org 
  Sent: Friday, February 04, 2005 3:35 PM
  Subject: DEPS (was RE: MK Dual Elavator)


  DEPS is hands down the best elevator system in my opinion.  Also, I would like to thank Troy for all his efforts in getting out a very nice, complete setup.  However, I think it can be made better with the Teflon sleeves.  

  I'm doing two Central installs in a couple Patriot roaches and I'm a little disappointed with both installs.  Neither are as friction free as last year's CST kit.  

  I had the luxury of installing these while the fuse was still an open box.  My support sleeves are about 21" long and I'd say you could measure the bend at the halfway point at less than a 1/4".  The push rods hit the center of the MK arms on the elevator (I haven't cut them to length yet.)  For all practical purposes, they are straight and dead on to the horn.  

  Yet there seems to be a lot of friction that needs to be overcome to move the assembly.  Once moving, it moves easily.  As such,  I'm concerned about centering.

  I was happy to see the graphite has worked for others and it may be just the ticket.  

    -----Original Message-----
    From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]On Behalf Of Troy A. Newman
    Sent: Friday, February 04, 2005 3:32 PM
    To: discussion at nsrca.org
    Subject: Re: MK Dual Elavator Bellcrank & Pushrod?


    Brian,

    sorry to hear you had some trouble with the guides on the DEPS.  We worked pretty hard on getting the system to be  easy to install and friction free. You are correct that any bending or curving in the system will cause it to bind up as stated in the instructions for the DEPS.  The Teflon sleeves have their own problems and what was happening is guys would wind the thread too tight on the Teflon sleeve and crush it. This would cause friction points along the length of the Teflon guide even it was dead straight. So the hard plastic guide kept this from occurring. 

    The key to both system is getting the pushrods at a straight shot to the control horns. NO bends no curves. If you install it this way it will be friction free. The right fuse exit location is so very important. I use a 4ft long straight edge to connect the dots from the servo connection location to the elevator control horn. I do this on both the side of fuse For the vertical location and angle and then the belly of the fuse for the fore and aft exit location. I use masking tape and project the lines to where I need to dremel the slot.

    This exit location will be very different depending on the location of the elevator servo up front and will also depend on the width of the fuse at the tail and where the elevator control horns are. So you need to have both mounted so you can align the rods to pass right by the connection points. No bending them over to it.

    A rough idea is my Supremes' have the exits about 10.5" forward of the elevator hinge line. A narrow fuse like a Focus of Temptation this exit will be slightly back further. The key is getting the slots in the right spot so it doesn't bend. 

    NOW some solutions I have heard of and never tried. Take the pushrods and slightly sand them with some 320 grit. "roll" the rod in your fingers....The ideal is not to sand diameter down but sometimes the pushrods can have some ridges on them from manufacturer. I think they are Pultruded (sp?) and this can cause some slight imperfections in the surface but I'm not sure.   I have seen  a  few of these with the CST rods. Never caused me any problems but I can see if the guides are curving it could.

    Next a little messy perhaps at first...Graphite dry lube like pine wood derby wheel lube works pretty good. Squirt a little in the tubes and the then install the pushrods. I heard of a guy doing this and he said it made all the difference. If you have to remove a glue joint on your pushrods to get it apart just heat the metal fitting up with a solder iron or a Bic lighter the glue will soften and you can remove the fitting. A little sand paper on the end where the glue was and the pushrod system will come right out of the guides from the front. Then deal with the guides and glue the ends back on. I recommend clean the old glue out of the hole. I use a drill...but be careful the titanium ends are very tough and you can break off a drill bit if you are trying to remove metal. I then use rubbing alcohol to clean it. Dry with a bic lighter and then glue it on again. Works fine.

    Next is sometimes you can get paint and crud in the tubes at the exits and this will cause some binding. Clean out the exit tube with a small round file....I have even used a long 2-56 pushrod threaded on one end to plunger the tubes and clear some debris.  I even saw one where the guy used some Thin CA to attach something and it ran down the CF rod and into the sleeves. It didn't glue it in place but it did cause quite a bit of binding. 


    I have not heard of guys having problems. Usually all you hear form this list and RCU is the bad stuff and rarely does the good comes through. I get tons of emails from guys that love it. I wondering if you try some of the fixes above and they solve your issue. I just installed this system on friends Angel Shadow and it works great! By the way Exits on it were about 11" forward of the elevator hinge line and they are a straight shot servo to the control horns.


    As for weight I just stuck the plastic tube guides on a scale and the Teflon guides as I have both. The Teflon one 4ft long was 6grams The Plastic one 40" long was 5grams....

    The 0.070" solid CF rods can't run unsupported for the length of the fuse. They will bow up when put under load. But inside the guides they are stiffer and more solid than any system I have ever seen or flown. This includes cables, MK, Dave Brown Fiberglass arrow shaft( the black one is fiberglass and not CF) And the CF rods  done like the Dave brown fork with a bushing support in the back. and supports in the middle too. The elevators get no differential between sides when under load and many of the other system do. This was the whole reason for using the DEPS system. Eliminate differential side to side and have a friction free slop free system that was light.

    Troy


      ----- Original Message ----- 
      From: Brian Billings 
      To: discussion at nsrca.org 
      Sent: Friday, February 04, 2005 11:33 AM
      Subject: Re: MK Dual Elavator Bellcrank & Pushrod?


      Speaking of the CF push rod set ups, I would like to share a little info. I just finished installing my second CF. elev. pushrod assem. in a Impact, the first was in my Majestic. In the Majestic I got the DEPS setup from CST seen here http://www.cstsales.com/CCPush-rodKits.htm
      This kit comes with a thin walled Teflon outer case and even with a slight bow or arc in the assem. the system remains Very friction free.
      For the Impact I purchased the kit from Central and it comes with plastic outer cases and these were difficult to get smooth and friction free, the slightest bend or arc made the movement very stiff and as a matter of fact, I could not even use them and ended up using hollow CF. rod for the outer case which worked very well but slight bends or arcs are out of the question. Just my personal experience, yours may differ.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.f3a.us/pipermail/nsrca-discussion/attachments/20050204/1273e35e/attachment-0001.html