Hi,

I have a Hangar 9 P-40 Warhawk and I have the retracts working OK, but I would like to take some of the load off the servo when it moves the wheels up and down. I know in some of the older retracts there was some sort of balancing spring that you could adjust.

Do you know if this can be added to the Hangar 9 retracts? If so, how do you do it?

Thanks for your help. Thanks.

Fly4Fun,

Wayne Miller

roll inverted on take off...[X(][X(]thats what I do anyway.....
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seriously, you could add a spring soewhere along the pushrod, where it would be convenient. The weight of the wheels will nuetralize the spring of course, so it shouldnt hurt anything that I can think of. Seems I would add an achor on the rod, and conect the spring to a fixed point, in the direction that will pull the wheels up. Now that im thinkin more....it may affect the down lock, but if the servo travels all the way to the lock position, iI dont forsee a problem. Hope that helps!
d

AH yes, a plausable solution... but remember for every action there is an opposite and equal reaction... spring tension to help retract, will need an equal force to over come spring when extending... what did you gain? A possible better solution... change push rod locations on servo out put arm and / or bell crank to gain mechjanical advantage.. Why fix it if it ain't broke???? Heh, Heh, Heh

Retract servos have a lot of torque anyway. They are designed to do one thing, swing 180 degrees. If you are using a retract servo there shouldn't be a problem with load; unless you have a bind in the linkage somewhere.

But if it bothers you there is the Robart air system you can put in.

there is a load present its normal it keep the gear locked in the up or down if you take the load off the gear will fold on landing and will come lose during flight

At full up or full down there is NO load, unless you have the linkage adjusted incorrectly.

You can put the retracts all the way down or up and remove the servo from the plane and they will stay down or up, unless vibration moves the over-center mechanism away from it's resting position.

If your servo has a load on it at either end, it will drain your battery quickly. Adjust the linkage so ti just makes it to each end without bottoming out.

Measure the distance the arm travels on the retract mechanisim.

Use a blank servo wheel and drill two holes, 180 degrees from each other the exact distance that the mechanisim travels.

Your setup should be perfect.

Hi,

I do appreciate your explaining how the retracts work, also explaining no load when up or down, the adjustments etc. etc. but this is stuff is common knowledge and not what I asked. The question I asked was, is there away to take the load off the servo when it is GOING up and down. I'm thinking of a detent spring or a load reducing balancing spring etc.

I was simply asking if anyone remembers how this used to be done, or any ideas how it can be done for the Hangar 9 P40 retracts.

What I want to do is reduce the load on the servo, thus reduce the amp draw so multiple retracions does not drain the battery prematurely. I know I can add a battery dedicated to the retracts, but I didn't want to do this.

The suggested idea of adding a spring may work.

If you do have any ideas, please let me know, I don't want to redesign something that has already been done. Thanks.

Fly4Fun,

Wayne Miller

If your servo is struggling, as mine was on the H9 P51, then get a 6 V battery. It will raise and lower the retracts with ease. Mine was not binding anywhwere, but the cheap H9 retracts can make life hard on a servo.

Someone mentioned this above, but I'll mention it again.

"You cannot get something for nothing".

If the spring helps the retract in one direction, it will hurt in the other direction.

Since the retract servo draws very little current when it is at its end points, the only other current draw as when it is in operation.

You only do this two times a flight.

Unless the servo gets stailed due to mis-adjusted linkage or a bent gear leg, current draw is minimal.

You are using a real retract servo, right?

Hi Dick,

I am using a JR Sport retract servo and it works just fine with no problems. As mentioned a couple of times, I just want to reduce the load on the servo.

As for getting something for nothing. We all know the retracts will have more load in one direction, due to gravity than the other, the intent is to "balance" the same up and down load, that's all.

As for a 6 volt battery, yes it will supply more power, but at the cost of a higher current drain. Basically a 4.8 v 1000mah battery in the same plane, will use less current and last longer than a 6 v 1000 mah battery, if all things are equal. The mah battery drain is what determines the length of time the battery will last. You can verify the 4.8 and 6 v drain by taking a look at the servo specs. But again, this is not what I am asking - all is working well, I just want to reduce the load.

I hope this clarifies the request.

Any ideas on how to "creatively" balance the load?

Fly4Fun,

Wayne Miller

Get these retracts:

http://www.3dxhobbies.com/store/cata...T_cat_310.html

Look at this video:

http://3dxhobbies.com/cart/media/Retract.wmv

Hi MinnFlyer,

That is what I am looking for, you notice in the picture, the balancing spring is built into in the retract unit. I'm sure I can find ome way to do this, but I didn't want to "reinvent the wheel" if someone else has already done it.

Thanks for the link and video.

Fly4Fun,

Wayne Miller

You would be surprised at how little the current draw increases with a 6 volt system compaired to a 4.8 on the order of 5 or 6 percent.

Balancing springs were used a lot on retracts with large wheels when servos weren't quite as powerful. Basically, you want the spring to be strong enough to balance the weight of the main gear when it's about 1/2-way retracted or slightly more. When extending the gear, you'll be 'fighting' the spring a bit, but not the entire load because the weight of the gear helps you. You can tell you need the assist spring because the servo strains when raising the gear. Lowering, though, should prove to be no problem.

Dave Platt, in his old RCM book, "Scale in Hand", discussed the topic. He may also say something about it in his current series of videos, but modern servos and pneumatic systems are strong enough to raise and lower all but the largest of retracts.

I have mechanicals in almost every plane i have plus a set of spring airs. They all work fine. What tension do you want? They lock up and they lock down. The way to adjust it is by adjusting the rod and or moving the connection in or out on the retract arms. It's a very simple process. I use GP Screw lock push rod connectors on the servo arms and adjust as necessary. Most of my rods usually end up on the outer hole of the retract servo arm.

I built that Warhawk for a buddy. Nothing to worry about on loads for that thing. Now I also have a GS WM P-51. Talk about a load. Thats a load. One retract servo for each wheel. Unless you want to flip your gear up and down through an entire flight, I don't think there is much to worry about on a volt load.