[LuvEvolution7]

this thread is started for anyone interested in learning how to make your own screw jack driven landing gear. anyone and everyone is welcome to provide anything they've built or ideas they have to share.

Rich

[Flypaper]

I built a set of scratchbuilt retracts for a 1/4 scale Focke wulf 190 D9. None of the commercial ones were close to scale. Very long legs with auto type coil springs on the outside. Legs are pultruded (,a wrap of carbon fibre around the outside), carbon fibre tube, very strong. The drives come from the planetary gearbox in those cheap electronic screwdrivers from CTC. The wheels on the FW are relatively large and thin as the wing on the full size FW is fairly thin. These are from the front wheels of a wheelchair from the old lady next door. Hope she doesn't miss them. A small lath and milling machine is handy but not necessary. I have a small Toyo lathe with a milling machine mounted on the back.
Here are some pics I took with a poor camera about 10 or 15 yrs ago when I built these. I'll take some better ones when I dimantle one to take more detailed pics.
In the meantime, any questions i'll be glad to answer.

Gord.

[Mike Sebastien]

Can you explain where you got the screw jack mechanism and it's operation? I'm presently building a PBY Catalina and trying to figure out how to retract the wing tip floats. A screw jack may be the answer.

[Flypaper]

The screwjack is made from 1/4 in. threaded rod using a slot cut with a hacksaw in the planetary drive output shaft and a 1/16 piano wire pressed crossways into a hole at the end of the threaded rod. Sort of a poormans universal joint. The brass piece in the 3rd pic is the moveable piece that lifts the gear up and down. The micro switches on top are hit by the brass piece to shut the motor off at the end of the travel. CTC has an electric screwdriver on sale now for under 10 bucks. The one that the head swivels about 45 degrees. Don't know what the drive is like, but I bought one to screw the wings on and off my planes out at the field. Lazy or what I'll take it apart to see if it's suitable. Best one are plastic case like the one shown above as the metal ones are fairly heavy. I'll take one apart to give a better idea of the slot and pin drive. The drive I bought back then had 2 pencells for power, so 3 volts. More than enough power because of the low reduction ratio. Very scale retract speed. Will do about 10 cycles before a recharge.
Hope this helps.

[Guest]

In building the screw jack landing gear some things to consider.

Advantages are a naturally slow motion and if the landing gear operate at differing speeds that is easy to do via resistors. Electric motors for activation are cheap I used older brushed motors for electric flight with a gear box and rather than use a universal joint I used a spur and pinion gear from an RC car set up. I also used a 5/16 national fine thread and turned the threaded rod into the landing gear leg to keep the size of the unit as small as possible when retracted. Tried it using a turning nut like a lead screw but the threaded shaft would stick out to far when retracted. The best advantage is there is no need for any type of lock to hold the position of the landing gear. In fact on large gear if you get your finger or any part of your body in the way its going to hurt.

The only real disadvantage is in the case of a rough landing and bent gear you will not be able to straighten the threaded shaft so make a few extra in case. I ordered a couple of lengths of stainless fine threaded rods for corrosion resistance and a little extra strength.

I am in Texas at the moment I think I may have a proto type steerable nose gear I built for a giant scale CL215 that had a water proof wheel well it retracted into. I will have to look and see when I get home.

Dennis

[Mike Emilio]

Hank Likes screwjack retracts.

http://findarticles.com/p/articles/m...9/ai_n8979143/

Likes Line, 1601 Airport Dr.,
Mechanicsburg, PA 17055;
(717) 732-0636

[Max]

Originally Posted by Mike Emilio

Hank Likes screwjack retracts.

http://findarticles.com/p/articles/m...9/ai_n8979143/

Likes Line, 1601 Airport Dr.,
Mechanicsburg, PA 17055;
(717) 732-0636

Is this guy still in business? from the link your provided it shows a link to the website, but I get "error 404- page not found" I see that the original article was written in 2001. Nice retracts if you can still get them!

[Guest]

Probably the all out best electric retract manufacturer

http://www.unitracts.co.uk/

[LuvEvolution7]

Gord

that's awesome. very nice design and not too expensive. the way you have that set up is exactly what I had in mind.............using two micro switches to determine end points. simple and effective. my problem is my brain is sometimes better than my skillset. LOL. in this case, my brain thought of the idea you have utilized, but seeing it in practice makes it easier to copy for my application. then there's wiring......now that's gonna ba an adventure. LOL.

Like's retracts are and are not still available. I have spoken to him on the phone within the last year and he'll still do gear for you, but his company is no longer in business. at least that's the last I heard. too bad cause it's good gear, but not cheap.

Rich

[Flypaper]

I just took one out of the wing and am about to break it down to parts. Being electrically unendowed my buddy made me a diagram for the wiring, where when one switch shuts off, it arms the other one. If I get close to a house electric outlet I get a shock When I worked for a marina and doing the timing on a 6 cyl Merc outboard, I had to stand on a stool to get the timing light to the flywheel. Pulled the trigger on the timing light and woke up on the floor due to a 40,000 volt jolt. Went through the timing light handle. Maybe it jolted something between my ears. Soon as I get it tore down I'll put up more detailed pics.

Gord.