ScottMcM

My Feedback: (66)

I'm installing mechanical retracts in my H9 T-34. I'm done with the retracts in the wing, and I used the proper retract servo (that I happened to have on hand). The nose gear is on a separate servo. Since it will technically need half the torque (one retract instead of two), why can't I use a standard servo, as long as I set the travel limits correctly? I don't have another retract servo handy, and I thought I'd ask before I ran out and bought one.

DavidAgar

My Feedback: (108)

Yes you can use a standard servo, however it is not advisable. A retract servo has more torque and shuts itself off at the end of it's cycle, where as a standard servo does not. A retract servo has more travel which is something you might need as well. It will cost a little to get another servo, but it is worth the investment. Good Luck, Dave

jetmech43

My Feedback: (9)

Ive used a standard servo on the nose retract amd using one now never had a problem

vertical grimmace

My Feedback: (1)

The problem is a standard servo can drain your RX battery during the flight. Especially if it stalls.

bassfisher

My Feedback: (21)

I totally agree with Dave. I personally only use Retract servos on retracts, the standard servo will just drain the battery down - usually at the worst possible moment. Better to spend $30 on a servo than trash a $300 investment using a $15 servo that is not designed for that kind of job. Just my 2 cents.

ScottMcM

My Feedback: (66)

I imagine I'll pick one up this weekend. Better safe than sorry, I guess.

DavidAgar

My Feedback: (108)

Yes sir Scott, I agree with your thought process, way better to be safe than sorry. By the time you add up everything that you put into a plane both as a money investment and as a time investment, to me it does not make sense to cut a corner or two to save $15.00 bucks and risk ruining all that you have gotten accomplished. Once again, Good Luck, Dave

ScottMcM

My Feedback: (66)

I really can't complain about buying a servo. I've been wanting to put retracts in the plane for a while now, but didn't want to spend the money. I got a killer deal on a large lot of planes and a big box full of rc "stuff" last week, and would you believe, there was a complete set of mechanical retracts, along with a retract servo. I guess I can splurge for another retract servo Isn't this a great hobby? This is the most fun I've had in years

bassfisher

My Feedback: (21)

Just a note - In the CMP T-34 thread and from experience from one our clubmembers, use 4-40 rod with metal clevis' for the pushrod from the servos to the retracts. Both Stallwart and I learned that the hard way. Especially if you are flying from a grass field. You'll like the T-34, they are great flying planes.

ScottMcM

My Feedback: (66)

Thanks for the tip.

jmupilot

HMMMMMM I only thought the servo was pulling current as long as it has to hold the postion of whatever is being moved, ie like a control surface. You use standard servo on your flaps dont ya. Its the same thing. I have a standard servo in my Long EZ nose retract, and have never had a problem. I just use the ETA(Endpoint Travel Adjustment) on my transmitter to limit the throw as much as It needs to be. the servo moves to that postion and stops no more current flows Now it you dont use the ETA it will hummmmmm and it then is using goobs of current. I think you can use a standard servo for retracts, just be sure you dont have the servo stalled at the full up or down postion. Most retract servos just dont have the feedback pot in them for centering. after all if you put a a current meter on one while deflecting the control surfaces you would see the current go up as it moves the go to zero when the centering pot reaches its feedback postion to match the signal from the rec.. now put pressure on the cotrol surface and the current goes up to try and hold the postion as the gear train moves from the force being put on the control arm They also have a gear ratio to provide lots of torque to raise the heavy mechanical gear.

Just my 2 cents test it and see for yourself

Pete

da Rock

Yes, it is possible to use a standard servo for gear, but they are quite a bit less suited to the job. Their range of motion is much less. The retract servo moves 180degrees. So however far out the servo arm your connection is, the amount of movement is double that. Easy to deal with that. Also, by having that connection in a straight line from the servo down the arm and down the pushrod, impacts that are transmitted up the pushrod have zero leverage and do no damage to the servo gears. A standard servo won't do 180 so you wind up with pushrod connections where impacts have improved leverage over the servo. And quite limited range of motion in comparison.

In a number of cases, getting enough range from a standard really is hard to do. And the farther out the servo arm you rig the connection, the harder it is to find the room, and the easier it is for the gear to destroy the servo if it doesn't lock. Keep in mind that if the gear doesn't lock up, the standard will work like crazy to keep them suckers up. And if the gear doesn't lock down, the landing force is going right into the servo. A retracts straight rigging takes the leverage out of both situations.

You can make do with a standard, and there is a temporary economy as well. But you wind up with more expense overall. I've got every retract servo I ever purchased and they're all going strong. It's quite normal to have to change out nosegear(rudder) servos every year or so. And it's fairly normal for flap servos to need watching over time to insure they don't cost you a lost plane from sucking down the airborne pack, and that happens often enough to show the problem would impact a plane using standard servos for gear.

If you're one who does maintenance and regularly checks his stuff, the standard servo for gear just risks the servo a bit more than the other normal uses.

Using the more expensive retract servos usually saves you money..... and airplanes.

sebo

I used a standard servo on one plane. The retracts drained the battery in one flight. Had I not checked the battery, I would not had more than one successful flight with that plane. Did it again on another date and had the same results. Replaced the servo. Now I have no worries. Use the proper servo.

Luftwaffe Oberst

I don't take chances. I only use retract servos for my landing gears. The difference between a retract and a regular servo is... well, take them both apart and compare.

Plus, a good retract servo like the JR NES-791 is supper strong, expensive but worth the $. There are retract servos on the market that are strong and not as expensive. I look at it this way and it is only my humble opinion.

You can go cheap, and use a regular servo for something that it wasn't designed to do... or you can get the right servo for the job it's recommended for, spend a bit more cash and not worry. It's your call, hope I helped.

jmupilot

Yep what you say is all true retract servos are made to do just that. The one I use is on a single nose gear retract for a LongEZ and the movement needed is far les than 180 degrees to pull up the nose gear. I was only commenting on the servo causeing the current drain. It was probly caused by a stalled servo rather than a standard servo being used. You set up a retract servo wrong and it almost has enough power to pull the control linkages apart. they are made to pull stumps (gear)up into the wings.

Pete

da Rock

It's not the 180 degrees that get the travel. The travel is a function of which hole you use on the servo arm.

The amount of radial movement provided by the servo has an effect, but it's not the only (or major) player. A standard servo doesn't give 180 degrees no matter what. And that causes a problem you have to deal with if you use the standard to do gear or flaps. And that problem can't be avoided, and is the primary reason standards so often drain the battery pack.

Using a standard, you have to rig the pushrod to make a 90degree angle with the servo arm at center-throw. If you don't, the servo won't give maximum throw to the pushrod. It also won't move the rod equally in each direction. All this makes adjusting your retract a real pain. And usually ends up with the worst case situation. The bloody mess either won't lock up, or won't lock down. And if either happens, you've got a servo that's at a mechanical disadvantage just when it needs the most advantage possible.

Using a standard takes some understanding. If you don't have it, and have little patience to learn, and no money to spare on setup mistakes, then save yourself some time and money. Get a retract servo.

ScottMcM

My Feedback: (66)

Thanks for all the advice, guys. I picked up a retract servo yesterday. I figure I'd better not press my luck.