flandrumjr

Problems with E-Flite electrict retracts.
Installed on Top Flite .60 P47 with Robart struts and 3" scale tires. Worked great to begin with but later began to drain the battery and I can only get about 5 cycles out of them before one stops short of the wheel well then less and less movement after that. Started with 4.8v and went to 6.0v as recommended by HH with no success. Anyone else had this problem? Called HH again and was told nothing could be done due to my modifying the intent of the retracts by attaching Robart struts. Don't understand that one. Never got the plane off the ground.

frets24

My Feedback: (15)

That sucks...thanks for the heads up.

In an earlier thread, where they were just intoducing the E-flights, some folks questioned whether there would ever be a strut ready cam block available for these and their answer was "no, the wire leg is of sufficient size to handle most manufacturer's struts and most struts come with a wire adapter anyway"...They went on to gush about how "robust" these retracts were and how well they would accomodate struts...especially in the 60-120 range...perfect for scale warbird builders. A bit of over reaching it seems...would love to hear others' experience...Maybe you just received a bum pair.

Lado actuators retrofitted into Robart retracts or "Down and Locked" seems to be the way to go....havent been hearing much positive on the E-flites from the field in scaled out warbirds.

http://www.downandlocked.com/

http://www.rcuniverse.com/magazine/a...rticle_id=1294

http://magnumrc.com/lado-electric-re...age=1&sort=20a

flandrumjr

Thanks for the information.
As far as getting a bum pair, I don't know, and am not prepared to spend another $150 to find out. HH promised to send me an e-mail with further explanations, will post that ifo if it comes. Although they have a 1 year warenty on manufactory defects they guy I taked to would not honer it and send a replacement pair (due to modification as decribed above), said they have no record of this problem reported. That is why I am shearching this site for information.
The E-Flite 60-120 retracts may be OK for wire struts only, but not with scale struts and wheels. E-flite should be more honest about the capabilities of these retracts and specefiy that scale struts and wheels may be too heavy after extended use, but that would't be good for sales. The R&D department didn't do there job on this one IMUO. They indicate 60-120 scale for these retracts, my TF P-47 is 60 and does not deliver, wonder how they figure the same retract will work on 120 scale with scale struts and wheels?
Very disapointed in E-Flite on this one.

SkyPilot101

Just another case of a company maximizing profit, eh Horizon! Many things are wittled down to save cost. I'd say they should start with a house cleaning of there customer service department.

jimmymac52

My Feedback: (4)

Flandrumjr,
I have the 60 - 120 eflites on my seagull 1.20 AT6. I am currently using the struts that came with the arf and added dubro low bounce 3.5 " wheels. The ARF-supplied struts are quite beefy and similar to robarts. However, I have the robart off-sets for this size on order because they are more scale-like. I have been testing the retract units with the ARF struts and have had no problems.

Have you checked the amp draw of each unit? I would start by checking the draw of each unit with and without struts and wheels to see if there is a variable. Then check the total draw for both units simultaneously. If the draw exceeds the specification, call them with that info. I'm sure they'll want to test it for you. One other possibility is that something is jamming the mechanism and the "over current protection" is being activated. Usually that protection feature produces a whine for about 5 seconds before it shuts down. Hope this helps

flandrumjr

Thanks for the info.
Not ready to give up on the retracts, just want to eliminate my inexperance as the problem. Let you know how it goes. Do you have a suggestion on how I may test the retracts for the draw-down as you described? Not too electricly inclined.

jbarnes

Using Robart struts on mine with 3.5" dubro wheels. 4.8v won't cut if for mine. I use a 6.6 A123 battery to power my receiver and run the retracts. Jerry.

flandrumjr

Did you experience the same problem with the 4.8v? Thats what I started with and was advised to go the the 6v 2000ma, but still having problems getting the retracts to come up in the wells even when full charge. Hope they are not worn out already, have been working with them for 3 months now. Yet to make the madian.

jimmymac52

My Feedback: (4)

Disconnect one of the retracts from the receiver and plug it into the load side of you volt meter and the plug the other side (power or batt) of the volt meter into the receiver retract channel. What you want to do is put the meter between the retract and the receiver. Now check the voltage drop and amperes being drawn as the one servo deploys and retracts. Then do the same for the other retract. Then, with both retracts plugged back into the receiver, connect your meter between your battery and your switch and deploy and retract both units and note the amperes used. Are your retracts bottoming out? Do they go into the over-current protection mode? you can tell because they produce a whine before they shut down also, your amps will spike and the voltage will momentarily drop.

flandrumjr

The retracts never make it to the wheel well. They begin retracting and get slower and slower, then about half way up they stop and do the "whinning" thing. I flip the switch and they go back down.
I'll try your sugestion and check the load. The V meter I have doesn't have a "load side". It just gives the volt reading to check the voltage of the battery. I'll see what I can come up with anyway.

Thanks again to all for your in-put.

jimmymac52

My Feedback: (4)

When you find the problem, let us know what it was. Someone else may be having the same problem. Thanks.........

flandrumjr

Checked the retracts with volt meter. I just taped into the end of the servo wire extensions conecting the retracts to the receiver with the volt meter as the retracts are presently installed for use. My reading with the 6v 2000 ma battery was 6.5v (fully charged battery). With retracts in the down position and the plane sitting up-right in the stand, I hit the switch to pull the retracts up. The meter whent to 5.5v and the retracts began pulling up. One stopped then the other both about 2/3 the way up, the whining" began and the v meter went to 4.8v to 4.9v. Flipted the swithch and one retract began to lower and the other did not move. Meter went to 5.5v. Got the "stuck" retract down by adding a little presure as the swith was on and in the down position. Repeated test with the same results.
Flipted the plane on its back and the retracts went up and down with no problem but straining against gravity when going into the down position. (remember plane is upside down). Meter went to 5.5v.
I appears that this set of retracts and incapable of lifting the Robart struts and wheels with the plane upright. Guess I'll have to invert in flight each time I want to pull the retracts up.
Don't know of anything else to try, I think at this point I will install a set of mechanical retracts so I can get this beautifl plane off the bench and in the air and send the retracts back to HH and ask for a refund.

Thanks again for the help and suport of all. I will let you know how HH reacts to this bit of information.

flandrumjr

Can anyone tell me if the readings I got on the volt meter are normal for these retracts?

FallDownGoBoom

My Feedback: (1)

A fully charged 6V pack should probably produce around 6.3V under "normal" load, which is proably between .3 and .5 amps. So it sounds like your the rest of your receiver/servo system is operating normally. My concern is that it probably takes a fair amount of amp draw to pull a healthy 6V pack down to 4.8V. Which is exactly what it sounds like your retracts are doing: the farther they get from vertical, the more torque is being put on the retract motor, so it starts trying to draw more amps, which drops the pack voltage.

To really tell what's going on, you need to use an ammeter/wattmeter to measure the the amps being drawn. If you know any electric flyers, they probably have something like a WattsUp, and may have the necessary jumpers/connectors to plug the meter between your battery and the receiver. The you could go back to H9 and ask how much current these electric retracts are expected to draw.

Part of the problem may be the wiring involved. Standard servo wires are 22-gauge, which is fine for .25-.5amp loads, which is what a normally operating servo will draw. But if the retracts are trying to pull current in the 2-3amp range, there may not be enough cross-section in the wires to deliver that much current.

Idris

I too am having serious problems with a pair of E Flite 6-120 electric retracts, including what seem to me to be several design errors, the most important being the grossly inefficient (6%?) lead screw system. This makes marginal operation, excessive current and the risk of flat batteries far worse than otherwise.

Rather than repeat my detailed analysis and fault symptoms here, I refer you to http://www.modelflying.co.uk/forums/...91&p=2#1218304

Idris

The following is my summing up, just posted in response to a chap on http://www.rcuniverse.com/forum/m_10...m.htm#11151185
who found when he dismantled his units that much of the problem arises from inadequate clearances on the moving parts, causing them to stick and jam.

"for information.

Thanks for your most helpful post, confirming as it does - and more - my findings. What follows is intended to be my final assessment of these units:

As before, the fundamental design error is the use of a lead-screw, notoriously inefficient at transmitting power because of high frictional losses inherent in rubbing the two threaded surfaces one on the other. Unless of course a ball-bearing lead screw were used, though unlikely to be available in this size or suitable for the forces involved if it were. Nor does the small size of the motor help efficiency.

Having now removed the drive motor and electronics (using a cutting disc as I cannot find a Hex key to remove the screws) I can confirm that what appears to be just a motor driving the in-line lead screw does in fact have a tiny 3 stage gearbox built in to the end. I suspect that in those small sizes with a small number of teeth efficiency is not too good, It is at least arguable that were the overall gear ratio and the thread pitch both twice as great the inefficiency would be significantly less and available pull significantly greater. In my view the speed could be halved to improve force, and still be fast enough (though as doubling the ratio would also double the force, speed would not fall by that same factor of 2)

This might go some way to reducing the several problems which arise from such low efficiency:

1/ The system struggles to overcome friction in the lead screw and (as you mention) in the locking pin etc. My own test on a complete unit, done by holding a finger lightly against the wheel when it is being raised, shows that available pull before stalling fluctuates a great deal - a graph would be a saw-tooth. This is because of the less than perfect fits and surface finishes moving one on another. In my case the margin for error - the difference between worst running current and electronic trip - was so small as to be unusable, the slightest touch would stop the wheel moving.

2/ 5 cells instead of 4 made marginal improvements but nothing like enough to make it reliable.

3/ One time in 6 or so, one leg or the other would refuse to unlock and extend.

4/ Unwanted cycling of the controls, presumably because of the electronic trip being activated, occurred quite frequently. At times merely the metal to metal contact of a screw touched against the mounting frame would cause one or other unit to cycle.

5/ On 4 cells the maximum current when the legs continued to move, for 2 units, was close to 1 Amp. When stalled 2 Amps with a buzzing sound until the trip activated after 2 seconds or so. On 5 cells it was 2.7 Amps.

6/ Because such currents would cause terminal voltage of normal Rx batteries to drop to dangerous levels - loss of decoding, delayed recovery, and slow throttle fail safe activating - I would not dream of operating them from the Rx battery even if I could make them work reliably - unless perhaps in the smallest size - and in my view and those of others I have read, using the Rx battery is just asking for trouble.



Having removed the motor and cut off its lead screw I could operate the unit by hand. It immediately became obvious that the transverse locking pin was marginally tight in it slot, on one side. This caused it to tilt, making things worse.

It was then also clear that the sharp corners in the frames between the locking slots and the transition slots were too tight. There is no need for the corner to be sharp, so careful work with a needle file freed the whole thing up. Before doing so, even without the undercart leg fitted, pulling the linkage free from the locks took significant force, afterwards no force to speak of.

On the second unit I found another problem - movement was stiff even without the u/c leg fitted. Slackening even very slightly the screws that hold the frames together eliminated the problem. This turned out to be because the two plain brass bearings set into the side plates were not quite flush, reducing the effective spacing by about 0.008" which was just enough to squeeze the pivoting trunnion. I linished them flush and solved the problem.
That the fit of these parts is so critical helps explain why some have problems and some do not - all depending on the clearances (which of course have to be minimal because of the 30 to 1 magnification seen at the wheel)

Having removed the drive system and freed up the mechanism I decided that marginal operation and unwanted cycling were simply not acceptable, and the obvious solution would be a more efficient motor with conventional gears. Fortunately I had precisely such a mechanism immediately to hand - a servo!

Initial tests showed that even with a 7" leg and 4 ounce wheel, a bog standard 60 degree Futaba ball race servo would handle the forces involved in one unit. A 17 kg cm 160 degree retract servo would of course do so with torque to spare. Because the aircraft in question is a TopFlite Thunderbolt 64" one, already built, it would have been very difficult to retro-fit the long linkages that would have to pass between the wheel wells and the upper skin to reach the centre servo bay, and bench tests showed that such long linkages need to be very stiff to prevent bowing that would prejudice secure locking at one end. And of course tricky to set up because the locking pins are not visible when installed in the wing.

Plan B was therefore to cut off one of the unwanted end of one of the frames and bolt directly to it one of the two retract servos I had to hand, so that the output arm of the servo was on the centre line of the retract unit. (A single nut and bolt will suffice as long as the far end of the servo is then supported in the wing.) By a stroke of luck I had a steel rod with a threaded end that matches the transverse pin and installed it as a push rod about 2" in length between the locking pin and the servo arm. These being proportional servos it was easy to match the travel to that of the locking positions before installing in the wing.

I had to cut away enough wing skin to allow the servo to fit, but not that much and not difficult to rework. I could have used the frame and servo to reinforce the strucure but on this wing it does not seem to be necessary.

I now have - at considerable overall expense in parts, time and frustration - undercarts which work every time, do not jam up, which lock precisely in place at either end and which have considerably more servo power available than they need - so much so that the servo does not noticeably slow down when lifting the leg. This incidentally confirms a point I made earlier, that the efficiency of the standard unit is of the order of single figure percentage points - because the servo arrangement is so much more efficient it wll not result in excessive drain from the Rx battery.

As for future retract models - at least one of the small cheap units, working on much the same principle as the mechanics of the E Flites, are entirely satisfactory in models up to say 56" span. At least that same unit can have grub screws fitted to adjust minutely the play at each end.

I cannot envisage paying E Flite prices for units that I then have to convert to servo operation after fine-tuning the fit of the parts - I did so on this one occasion because it was the easiest way out of where I had found myself.

I have taken a few photographs that I could put on my web site if anyone wishes.

If on the other hand E Flite decide to offer just the mechanisms without the drive system - as Robart do as an alternative to their pneumatic retracts - and at a significantly lower price, then they would be an attractive option. Especially if the frames were arranged to accept servos bolted on.

All of this and previous postings are of course only my opinion, others are free to disagree, and I have no commercial reasons whateever for making these observations.

Sorry if anyone thinks this long-winded, but I tried to make it complete in itself and as helpful as possible. I will put the same on the few other web sites where I have seen this subject raised.


Idris
















The following is my summing up, just posted in response to a chap on http://www.rcuniverse.com/forum/m_10...m.htm#11151185
who found when he dismantled his units that much of the problem arises from inadequate clearances on the moving parts, causing them to stick and jam.

"for information.

Thanks for your most helpful post, confirming as it does - and more - my findings. What follows is intended to be my final assessment of these units:

As before, the fundamental design error is the use of a lead-screw, notoriously inefficient at transmitting power because of high frictional losses inherent in rubbing the two threaded surfaces one on the other. Unless of course a ball-bearing lead screw were used, though unlikely to be available in this size or suitable for the forces involved if it were. Nor does the small size of the motor help efficiency.

Having now removed the drive motor and electronics (using a cutting disc as I cannot find a Hex key to remove the screws) I can confirm that what appears to be just a motor driving the in-line lead screw does in fact have a tiny 3 stage gearbox built in to the end. I suspect that in those small sizes with a small number of teeth efficiency is not too good, It is at least arguable that were the overall gear ratio and the thread pitch both twice as great the inefficiency would be significantly less and available pull significantly greater. In my view the speed could be halved to improve force, and still be fast enough (though as doubling the ratio would also double the force, speed would not fall by that same factor of 2)

This might go some way to reducing the several problems which arise from such low efficiency:

1/ The system struggles to overcome friction in the lead screw and (as you mention) in the locking pin etc. My own test on a complete unit, done by holding a finger lightly against the wheel when it is being raised, shows that available pull before stalling fluctuates a great deal - a graph would be a saw-tooth. This is because of the less than perfect fits and surface finishes moving one on another. In my case the margin for error - the difference between worst running current and electronic trip - was so small as to be unusable, the slightest touch would stop the wheel moving.

2/ 5 cells instead of 4 made marginal improvements but nothing like enough to make it reliable.

3/ One time in 6 or so, one leg or the other would refuse to unlock and extend.

4/ Unwanted cycling of the controls, presumably because of the electronic trip being activated, occurred quite frequently. At times merely the metal to metal contact of a screw touched against the mounting frame would cause one or other unit to cycle.

5/ On 4 cells the maximum current when the legs continued to move, for 2 units, was close to 1 Amp. When stalled 2 Amps with a buzzing sound until the trip activated after 2 seconds or so. On 5 cells it was 2.7 Amps.

6/ Because such currents would cause terminal voltage of normal Rx batteries to drop to dangerous levels - loss of decoding, delayed recovery, and slow throttle fail safe activating - I would not dream of operating them from the Rx battery even if I could make them work reliably - unless perhaps in the smallest size - and in my view and those of others I have read, using the Rx battery is just asking for trouble.



Having removed the motor and cut off its lead screw I could operate the unit by hand. It immediately became obvious that the transverse locking pin was marginally tight in it slot, on one side. This caused it to tilt, making things worse.

It was then also clear that the sharp corners in the frames between the locking slots and the transition slots were too tight. There is no need for the corner to be sharp, so careful work with a needle file freed the whole thing up. Before doing so, even without the undercart leg fitted, pulling the linkage free from the locks took significant force, afterwards no force to speak of.
On the second unit I found another problem - movement was stiff even without the u/c leg fitted. Slackening even very slightly the screws that hold the frames together eliminated the problem. This turned out to be because the two plain brass bearings set into the side plates were not quite flush, reducing the effective spacing by about 0.008" which was just enough to squeeze the pivoting trunnion. I linished them flush and solved the problem.
That the fit of these parts is so critical helps explain why some have problems and some do not - all depending on the clearances (which of course have to be minimal because of the 30 to 1 magnification seen at the wheel)

Having removed the drive system and freed up the mechanism I decided that marginal operation and unwanted cycling were simply not acceptable, and the obvious solution would be a more efficient motor with conventional gears. Fortunately I had precisely such a mechanism immediately to hand - a servo!

Initial tests showed that even with a 7" leg and 4 ounce wheel, a bog standard 60 degree Futaba ball race servo would handle the forces involved in one unit. A 17 kg cm 160 degree retract servo would of course do so with torque to spare. Because the aircraft in question is a TopFlite Thunderbolt 64" one, already built, it would have been very difficult to retro-fit the long linkages that would have to pass between the wheel wells and the upper skin to reach the centre servo bay, and bench tests showed that such long linkages need to be very stiff to prevent bowing that would prejudice secure locking at one end. And of course tricky to set up because the locking pins are not visible when installed in the wing.

Plan B was therefore to cut off one of the unwanted end of one of the frames and bolt directly to it one of the two retract servos I had to hand, so that the output arm of the servo was on the centre line of the retract unit. (A single nut and bolt will suffice as long as the far end of the servo is then supported in the wing.) By a stroke of luck I had a steel rod with a threaded end that matches the transverse pin and installed it as a push rod about 2" in length between the locking pin and the servo arm. These being proportional servos it was easy to match the travel to that of the locking positions before installing in the wing.

I had to cut away enough wing skin to allow the servo to fit, but not that much and not difficult to rework. I could have used the frame and servo to reinforce the strucure but on this wing it does not seem to be necessary.

I now have - at considerable overall expense in parts, time and frustration - undercarts which work every time, do not jam up, which lock precisely in place at either end and which have considerably more servo power available than they need - so much so that the servo does not noticeably slow down when lifting the leg. This incidentally confirms a point I made earlier, that the efficiency of the standard unit is of the order of single figure percentage points - because the servo arrangement is so much more efficient it wll not result in excessive drain from the Rx battery.

As for future retract models - at least one of the small cheap units, working on much the same principle as the mechanics of the E Flites, are entirely satisfactory in models up to say 56" span. At least that same unit can have grub screws fitted to adjust minutely the play at each end.

I cannot envisage paying E Flite prices for units that I then have to convert to servo operation after fine-tuning the fit of the parts - I did so on this one occasion because it was the easiest way out of where I had found myself.

I have taken a few photographs that I could put on my web site if anyone wishes.

If on the other hand E Flite decide to offer just the mechanisms without the drive system - as Robart do as an alternative to their pneumatic retracts - and at a significantly lower price, then they would be an attractive option. Especially if the frames were arranged to accept servos bolted on.

All of this and previous postings are of course only my opinion, others are free to disagree, and I have no commercial reasons whateever for making these observations.

Sorry if anyone thinks this long-winded, but I tried to make it complete in itself and as helpful as possible. I will put the same on the few other web sites where I have seen this subject raised.


Idris


and another problem found after posting the above:

and one more problem! When fettling the 2nd unit this evening I realised that movement was quite stiff even without an U/C leg attached. As others have done I loosened the frame screws and the stiffness disappeared.

Using digital calipers I established that the distance between the two frame parts provided just enough clearance for the trunnion and its to think plastic shims - but the brass bearings force fitted into the frame parts were about 4 thou each proud of the surfaces, reducing the spacing by 8 though - enough to make movement noticeably stiff. The plastic shims spacing the trunnion from the brass bearing would not have worn so the stiffness would not ease with use.

I fixed it by using linishing the brass bearings flush with the frame.

What it comes down to I suppose is a lack of adequate quality control when making items with fine tolerances - I suspect though it is too late now to check, that the operating currents were significantly higher than they should have been.

Idris

Idris

I have found yet more lproblems, but the summary is too long to file here so I have made it available at http://www.fightbackwithfacts.com/re...ctor-problems/.

The same subjects have been discussed at

http://www.rcuniverse.com/forum/fb.asp?m=11184956

http://www.rcuniverse.com/forum/m_11...m.htm#11134586

http://www.rcuniverse.com/forum/m_10...m.htm#10583216

http://www.rcuniverse.com/forum/m_10...m.htm#10549512

http://www.modelflying.co.uk/forums/...91&p=2#1218194