Hello.

A real newbie question.

For a tricycle landing gear arrangement, say like on an Avistar 40,
is it typical for the front wheel diameter to be slightly smaller than
the two rear wheels? Also, should the plane be sitting slightly
lower towards the front to help keep the nose down?

I want to replace the 'foamy' ARF wheels with Dubro's, like 3 1/2"
dia. in back and say 3" in front to help with the grass landings at
the field. Just wanna make sure this makes sense!

Thanks for any input!

every airplane is different but yes it is common for the nose gear to be smaller.
when upsizing gear keep the same difference, ie: if your stock nose gear is 1/2" smaller than your mains make sure your upscale wheels have that same 1/2" difference. That way the angle the plane sits at will be the same. Make sure to check the balance because of the added weight.

SLIGHTLY smaller is ok. Larger is even ok if you run through tall or thick grass on your runway. The plane should sit level or SLIGHTLY nose down. NEVER nose up. If it sits nose up, it will tend to take off too quickly (stall, snap, crunch) and be hard to stick on the runway when landing. If it sits too much nose down, it will take a lot of elevator to horse it off. When it does come up, it will be quick and in a steep climb.

Dr.1

Thanks for the replies all!

Kinda noticed the wheel size differences but didn't know if there was
a logical rule of thumb, or any rhyme or reason to it.

Kinda goes back to full scale. On full scale the main gear supports almost all of the weight of the plane. The nose or tail wheel is there to keep it from falling on it's nose or tail when parked or moving. Less loading requires a smaller tire. Look at the HUGE airliners. BIG multiple truck landing gear assemblies and one spindly little nose strut with maybe 2 relatively small wheels on it. There would only be one but they are big on redundancy in case one goes flat.

Less loading requires a smaller tire.

Full scale planes don't have to worry about running through bumpy or heavy/long grass. A big nose wheels helps our models in this situation.

Dr.1

They don't? Ever heard of "bush planes"? They operate almost exclusively off very rough undeveloped fields using "tundra tires" among ather things.
http://en.wikipedia.org/wiki/Tundra_tires
There are a number of planes that have been adopted for "bush" usage.

Bumpy and heavy/long grass? They would consider that smooth in many cases. Ever see a plane take off out of a corn field with 4 ft tall corn stalks in it? I have. Not a normal proceedure but 2 days after an emergency landing due to smoke in the plane.

[quote]ORIGINAL: bruce88123


I thought that they banned smoking on planes!!!! [X(]

Ken

[quote]ORIGINAL: RCKen


That's why they had to land and kick the guy off the plane.

Actually it turned out to be some overheating components in the air-conditioning system. Took a day to get parts to the plane, another to install. Got permission from the farmer to knock down a few rows of corn and flew the plane out of the field. DHC-6, a STOL plane.