Flypaper 2

Here's the picture

JNorton

My Feedback: (2)

Jim,
Could you enlarge the top plate of a normal servo to use additional gearing (stolen from another servo) to drive an externally mounted pot? If you get the ratios right it will work. Just figure out how many turns per inch etc etc.

Flypaper2,
Good looking jackscrew. It doesn't show the switches clearly enough for me to trace it.
If you look at the drawing in post 16 at the CCW limit switch - it is shown as if the leadscrew had open it at the end of its travel. Great the circuit stopped the travel of the screw. Now let's reverse it. The switch is still open, the DC motor can't move to reverse direction! Now look at the drawing in post 12. The servo controlled reversing switch can move in either direction as power to it has not been cut. Look at the extra contacts that parallel the CW and CCW limit switches. They are wired so that when the servo driven reversing switch is moved the open limit switch on the DC motor is jumpered - closing the circuit and the lead screw will reverse.

John

JimTrainor

Yes, something like that would work.

Sort of like this:

http://www.servocity.com/html/power_gearbox_servos.html

If you drive a normal rotary pot off an external gear, and run the lead screw directly off the servo's output shaft then you've got it.

JNorton

My Feedback: (2)

Hey if you build it I want a photograph!
Fun fun fun,
John

Flypaper 2

John:
Sorry for the name mistake. One of my buddys is an instrument technician and made the schematic for me and can't find it. But the wiring on the gear looks like 16 except one of the motor terminals goes to both microswitches directly. The other side of each microswitch goes to either side of the toggle switch.
Jay:
These motors are on two cells, 2.4 volts. I'd estimate jackscrew turns at about 180 rpm. Will cycle half a doz. times on a charge. cells are AA size. Gear legs are 16 ins. to ground with front wheels from a wheelchair. Only ones I could find narrow enough to go inside the wheelwells.

FHHuber

The "lobotomized" servo can have the brain reimplanted for endpoints. you could just move the pot out of the servo case and spring load it to center... and then have approaching a limit pull the pot's operating arm to a side and... it will slow down the motor, then stop when you hit the limit (you could even make the darn thing FULLY proportional!)

Possibilities are endless if you think about it...

***********

Someone mentioned most of this... just not the use of the original Pot... I hadn't read past the one that suggested the lobotomized servo in the first place.

JayGull

My Feedback: (3)

Flypaper2, where did you get those type motors? Would they handle more voltage if you needed it? I was thinking about labatomizing some 2.4 or 3.6 volt screwdrivers to get the motors.

Jay

JimTrainor

What are you guys doing with these screwdriver motors and gear boxes?

I can see the attraction, but they seem pretty hefty for a model.

Mike James

Several of us had them in mind for scale operation of slotted flaps, and one person above mentioned using it to control an in-flight CG-changing device.

Flypaper 2

Jay: These are from powered screwdrivers 2.4 volts, speed 400 size motor. the planetary gear box is 1.400 dia. the batts. you see in the picture go under the gearleg with the charge jack. Guessing it turns about 180 rpm. lots of torque at that speed. Either end of the 3/16 screw has a 1/8 in. ID ball brg to take a lot of end thrust, as in the weight of a 13 in. long gearleg with a 6 in front wheel from the front of a wheelchair. Don't laugh as it was the only wheel I could find narrow enough to go in the wheelwell. FW 190 had a thin wing with narrow wheels. To connect them , a slot is cut in the hollow output stub of the gearbox. A hole is crossdrilled through the screw and a 1/16 piece of piano wire is pressed into it for a crossbar. Sort of a poormans universal joint. I'm sure the motor could take higher voltage for more power. What's the span of the Corsair wing that needs to be lifted? Hope this helps.
PS the whole assy, wheel and all weighs 1 lb. 3 oz.

JayGull

My Feedback: (3)

Flypaper2, again thanks for the info. The Corsair is still under design development. And the folding wing is maybe a pipe dream but I really want to try it before I rule it out. The wingspan will be 123" and will fold at the scale location just outside of the gear and the gull. without measuring I would guess the wing panel that would have to be lifted is around 40". I dont expect it to be very heavy though based on the contruction method as I am using enlarged Ziroli plans. The entire wing fold mechanism will function as the full scale did, that is two hingpoints and a locking mechanism at the lower spar. I was originally thinking of using air but I dont think I can get the power I need. So I guess now I just need to find a 2.4 volt motor and get to testing.

Jay