Model Airplane Retract Plans

[Starwoes]

Anyone got any dwgs or basic design of a model airplane retract that he/she is willing to share? Will appreciate it much

Ta

[Starwoes]

Ok i sat down, looked at a few pictures and designed my own. It is incomplete and I will probably fiddle with it some more before i cut metal. It works well in a computer aided program though. Most of the holes shown on the side are lightening holes -- it will actually be held together by 3 or 4 socket head screws.

the final form will rotate 90 degrees as it retracts. Suggestions for improvements, need files as a starting point? etc?... let me know i am willing to share and also improve on this. thanks.........

[miljnor]

what are the slots for at the end of travel?

If they are what I think they are for (locking) I would do it a different way.

Most retracts that I've seen use some form of over travel on the cam to make it so they are self locking.

This means that when the air cylinder pushes the wheel into the full down position it travels just a little further past the center point of its fulcrum, making it lock in place. That way if force is applied to the wheel arm it actually just makes it lock down harder.

[Starwoes]

you are right, they are for locking. the pin floats and additional force applied allows it to travel that little extra into the groove to help hold things in place. I believe I understand what you are saying but if you could, please provide a cursory sketch as a picture says a thousand words.........


thanks

[miljnor]

I probably don't have time in the next couple of days for a sketch but I have been staring at your drawings for awhile and think that if you change it slightly you will achieve the same thing but with fewer parts.

take the end of the pushrod from you cylinder and relalign everything so that the cross pin IS the pushrods (from the cylinder) pivot point. And then make the hole in the retract sloted so that when the end of travel is reached it slides up into your slot with the air cylinder pushing it in.

What program are you using? If its solidworks or something with a compatable file type send it to me and I will modify it for you to give you an idea. I will try to draw something but I am very busy for the next few days.

[miljnor]

This is kind of what I am talking about. The only thing you might have to change is the angle of the lockout (might have to reduce it. So as not to cause any undo sticking.

[miljnor]

i also emailed the files back to you... you get the idea..

Not much of a change but this is how a lot of locking clamps lock out. The other way I was thinking is by camming past the fulcrum point. If I have a chance I will post some more modifications that show that design.

[Starwoes]

thanks for your input. will check my mail shortly.

/Fr

[miljnor]

if you havn't gotten it yet it aint coming. let me know and I will remail it to you.

[vulcom1]

I made my own for a model of mine and the main gear use's 5" wheels with screwdriver planatary's and jack screw's. Basically the same but a little rough to your drawings but they work except they are electric. Not sure if the picture shows but they use the over travel as explained before I believe.
Also I used countersunk ss screws on the frame as if you use cap screws on the sides you need more clearance. To me this weakens the structure.
John

[miljnor]

thats sweet man!

I want to see pictures of the plane though! ITs got to be big with 5" wheels. Those retracts are monsters! (at least to me as I am into electric park flyer size stuff)

[vulcom1]

This is my on going project. 2 years but not steady as I am building a 30%Raven aerobatic(87"ws) from my drawings also. This is a CF100 that is 1/5th scale with a wingspan of 149". It has been epoxy/glass covered and the fuse has most of the primer removed. When done will have 2 KJ66's for power which I am also working on. Even though I am medically retired(sholder) there does not seem to be enough time.
John