Shock Absorbing Landing Gear

[Chancey Chorney]

Hi again. As you may already know, I am building a Ringmaster Jr. I am at the point of doping the fuselage and covering the wing. However, I have one question regarding the mounting of the landing gear. The plans indicate a plastic retainer to hold the landing gear in place. However, I was wondering if it would be ok to do it such as the way the Lil' Jumpin' Bean landing gear with a dowel and rubber band to hold in place. Is there any reason I cannot do it this way? Or is it better to just do it the way indicated on the plans? I just thought doing it with teh rubber band would be better for those less-than-stellar landings that I will probably throw at it. Thank you.

[Brett Buck]

Hi again. As you may already know, I am building a Ringmaster Jr. I am at the point of doping the fuselage and covering the wing. However, I have one question regarding the mounting of the landing gear. The plans indicate a plastic retainer to hold the landing gear in place. However, I was wondering if it would be ok to do it such as the way the Lil' Jumpin' Bean landing gear with a dowel and rubber band to hold in place. Is there any reason I cannot do it this way? Or is it better to just do it the way indicated on the plans? I just thought doing it with teh rubber band would be better for those less-than-stellar landings that I will probably throw at it. Thank you.

    That will work, but it's pretty bouncy even as it is. Presumably you are using 3/32 wire as in the other thread. If you have sufficiently reinforced the nose/wing LE joint to keep the nose on it, the landing loads transmitted through the very springy wire will not likely cause any additional problems.

   Note that the rubber band mounting is not at all shock-absorbing in the usual sense. It's just adding additional springs, no damping, to all it does is make it bounce even higher when you land on pavement. What it may do it prevent the gear from getting bent as quickly.

   These sorts of landing gear arrangements (intended to avoid nose-overs on takeoff and keep the prop from hitting the ground) are absolutely diabolical to land on pavement. The usual result is severe bounces, enhanced by PIO. But on very rare occasions, it just greases in. Just often enough to keep people from giving up on it completely. After all, once you know it can be done, then you just have to control it properly. But the more you try to control it, the worse it gets!

     Brett

[Chancey Chorney]

Ok. Thank you for the help and advice.

Brett, yes, I am using 3/32 rod as per the other thread. I did make up a set using 1/16 and it was way too flexible! So I sourced out a piece of wire from a friend and formed it. It does seem good and springy. As for you asking if I sufficiently reinforced the nose/wing LE joint to keep the nose on, I cannot honestly answer that as I do not really know what you are asking. I did not build the fuselage, but can say with certainty that the gentleman who did would have done things right. With that said, I will leave you with the following. Fuselage is 3/8 balsa with 1/16 doublers on both sides. Wing has a solid 1 piece 1/4 square LE spar, 1/16" hard sheeting from LE to Center spar both top and bottom. I hope this may be of some help in your question. The wing is not yet mounted permanently. The only other thing I was thinking of doing is to file a small notch (3/32) into the center of the wing cut-out and put the LG wire in it and fill it with epoxy once mounted in place. Thanks again.

[Steve Helmick]

The wing construction described does NOT sound like the original Sterling kit. Leads me to ask what kit it is.

As before, I would suggest sheet aluminum LG struts. They give vertical flexibility with no rearward flex. This keeps the wheels pointing in the correct direction to actually roll, as intended. The wire LG when flexed will tend to toe-out the wheels and drag them sideways, not rolling. That results in the plane nosing over at best...the good thing about the Ringmaster is that the shape of the fin/rudder makes a good skid when sliding backwards & upside down after a nose-over.  Steve

[phil c]

I think Goldberg pioneered the rubber band restraint on the landing gear.  I believe they did it to prevent the gear from getting bent on nearly every neophyte "landing".  Some fliers fatigued the fixed gear on a Ringmaster in a short time and one or the other leg broke off.  The rubber band allowed the gear to bend back and punch holes in the covering.  Not really much of an improvement.

Aluminum gear is fine if it is properly bent and tempered.  Regular aircraft aluminum, 6061 can be had untempered or tempered, usually 651T.   Most readily available aluminum mechanically worked and then tempered.  About all you can do in the home shop is bend it, no more than 45deg., around a radius, using some heat(less than 500 degF).  Too much heat it will lose the temper and work hardening and that can't be fixed at home.  A lot of people bend it 45deg and then bolt the pieces on either side of a profile fuselage.

If you can find prebent aluminum blanks that can be cut to shape that is the easiest solution.

[pat king]

The original Ringmaster S1 had 3/32 music wire gear. It had so much flex that pulling out of a loop 2 to 3" too low would put the wheels through the covering on the bottom of the wing. I did that more than once. The Original Ringmaster Jr. S5 appears to have had 5/64 music wire gear. When I did my Ringmaster Jr. I used 3/32 music wire for the gear to help resist flexing far enough to put the wheels through the bottom of the wing. The rubber band method should be good for holes in the bottom of the wing on any rough landing. The Ringmaster Jr. mounted the gear like the S1, notch in front of the wing then shown as being bound with copper wire through the doublers. The attached shows the gear wire from an original kit.

Pat