The +'s and -'s of electric retracts on large jets - Page 3 - RC Groups
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Mar 16, 2011, 11:09 AM
Capt. Z
falcon5's Avatar
Big planes are no probblem for servo operated retracts or electric retracts , I have one of each, the servo operated retracts and servo operated gear doors on a 15 1/2 pound F-4 and love em. I use the E-flight electrics with Tam struts on a 8 1/4 pound Hawk and love those also. Set them up right from the start and forget about em'

Will NEVER go back to air again. well not unles I have too,
Last edited by falcon5; Mar 16, 2011 at 12:36 PM.
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Mar 16, 2011, 12:39 PM
You are a "go" for reentry
Maxthrottle's Avatar
@lightningmcnul: I do look for running reports of failures so any details would be helpful re the stripped Eflites.
Which ones were being used, weight of model, were shock struts used....

The earlier models had a plastic block that could potentially be stripped but I thought they had a metal block/nut now.

Just a guess but the plastic trunnion may been crushed or broke off the metal locking block that transitions over the worm gear. Most of the current ones to strip the worm gear would be like stripping a hardened 2mm or 2/56 threaded rod and some how stripping a nut off of it.
The way they made to loads the block in the housing not the worm gear until it passes 50% retraction. Its like air retracts the piston doesn't see the load, the slider track does.
It would be better though if at least the trunnion, block and worm gear were of decent metal.

I used a RCL above its 2.5Kg rating and crushed the trunnion tips which then slipped over the block worm gear mech. I later replaced just the trunnion since everthing else was fine. The cause was the original strut rod was of a soft metal, got bent and damaged the trunnion from the extra weight.
I later pancake land the same setup in a early crop of soy. Bent up the strut but everything was still fine.

From that my thinking was use them with their limit, metal trunnion, block and thicker worm gear are better. Use good shock struts.
The 15-20, 46-60 and PZ15091 gets by because it plastic trunnion is wider, ~14mm, and takes a 4 or 5mm strut. Some of them are made similar to the Robart 608s that used a plastic trunnion and block. They had their limits to.

Again this is not to say they impervious or that your report is in anyway in accurate.
Mar 17, 2011, 11:51 AM
Registered User
Hey Maxthrottle

I believe that they were eflight 15-20 size and they were in a stock sapac 70mm hawk and a similar sized l39.

also note that on both occasions eflight replaced the damaged items for free

thats great that they are already improving them, i knew they would, its always the same when new items come on the market, especially when they are a whole new idea.

since they are so simple I'm sure in a very short time there will be little to no problems with the electrics, just need them to make some big enough for my 1/4 mustang!

Mar 17, 2011, 01:25 PM
You are a "go" for reentry
Maxthrottle's Avatar
Originally Posted by lightningmcnul
..., just need them to make some big enough for my 1/4 mustang!

Thanks. Because of the Eflite price range I would hope the replacements under warranty would be free. But then ChangeSun did the same also replacing the v1 plastic trunnions for the metal ones.
The PZs at $7 ea I just buy a bunch of them and exchange parts if necessary, which actually hasn't happened yet.

Have you looked at the Lado's. Magnum site has Lado etracts for the 25%+ class (20kg/45lbs) or even the piston replacement to work with most existing air retracts. For a setup like that I'd have the lighting and etract system driven off a separate power source or some sort of central regulator.
Mar 17, 2011, 04:55 PM
1.21 Gigawatts!
Steph280's Avatar
maxthrottle have you had any of the PZ or Changesun's endpoint sensor switch fall off of the circuit board? Specially when they are used in the nose. Seems the impact is passed onto the switch which breaks them.
Mar 18, 2011, 12:27 AM
You are a "go" for reentry
Maxthrottle's Avatar
Originally Posted by Steph280
maxthrottle have you had any of the PZ or Changesun's endpoint sensor switch fall off of the circuit board? Specially when they are used in the nose. Seems the impact is passed onto the switch which breaks them.
Actually I looked up the info on the Hawk. Its 2.6-2.8Kg. But to be fair it looks like the retracted stop sensor ws the one that broke so it should being seeing any load.....??????

In the comprehesive list I had the links to threads that show pictures of the insides of these various etracts.

The early versions, had a pointed tip on the trunnion that had the transition block press the trunnion in the lock position which translated a good portion of force to the worm gear directly and if you sequenced your gear aft, the trunnion would impact the block which could pop the sensor. For me, the Trunnion tip broke off on my with RCLanders PZ15090s and partially calapsed instead of breaking the sensor. But that may not happen with everyone.

This was primarily for PZs by the way. CS etracts have a larger block and is shaped that it is a block on a block or a square flat faced trunnion locked in place be a larger flat faced transition block. This was similar to how Robart made their 608s. But CSs were made of all plastic and couldn't hold the strut with just the grub screw. Thus they went to a metal trunnion and block.

I think PZ realized the issue and remade their trunnion to have a more square face but it is still very narrow. Thus if the trunnion slips off the block you again could direct force to the worm gear and possibly the sensor if the gear swung back. But the amount of force is more like a soft crash than a rough landing.

The Freewing etract has the newer PZ trunnion but a solid block of metal to transition and lock the trunnion. So for the number sold, they appear to also being doing well with the larger flat faced transition bock shape.

Depending on which Eflite, their lock or transition block is also more square which is partly why I guess they have less reports of this sort of fail. So its for these reasons its my guess that the defect of popped sensors is during manufacturing. Some just resolder them back on.

I do give HH Eflites koodos for that. They do seem to have less of those incidents reaching the customer because they either pay more to make certain they are solderd on correctly the first time or they QA and reject.

But when you can get 8 sets of PZs to one of theirs I took the chance of going cheap and so far its worked. But thats just me.

Looking at most of them now, impact force is translated more to the trunnion, the transition block and the housing that the block slides along and not the worm gear and thus not the sensor. The worm gear just positions the block. But like all retracts, air or electric, the mechanics is at its weakest point during the transition because force can be translated to the transiton device, worm gear or piston. Thats where unintended impact force can do the most damage to the transition apparatus.
Last edited by Maxthrottle; Mar 18, 2011 at 12:47 AM.
Jan 23, 2015, 06:17 AM
Registered User
What is the best way to attach a servo to the gear door? A solid rod, or loose wire?

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