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gphil 10-08-2012 03:42 PM

Bolt on axle
 
My conventional gear plane just will not taxi well in our grass field. C.G. is good etc but noses over if not careful. One of the fellas said get some bigger wheels. I have some 4" and 3" wheels but what I discovered because I did not look is the axles from Debro I have are short for the larger wheel. I think I need the 3/16x2 size for the 4 incher not sure about the other. What is your thoughts here and how to the ajustable axles work. When I get finished with this plane, I will be a expert for sure. gphil

alan0899 10-08-2012 04:24 PM

RE: Bolt on axle
 
G'day Mate,
By conventional, do you mean Trike gear, or Tail dragger.
Whatever, you have, if the landing gear is wire, I see a problem, but if it is Alloy with bolt on axles, just buy new axles, the size that matches the holes in your larger wheels.
If it is a tail dragger, you must hold full UP elevator while taxiing.

Cheers

gphil 10-08-2012 04:52 PM

RE: Bolt on axle
 
Yes it is a tail drager , conventional, as they say.    I do hold full up but prior a guy changed the throws on the controls and I think I do not have enough "up" anymore.   The larger wheels measure for 1/8 hole but that is way too small.   Reason I say that is I have some that size and I am thinking wrong parts in pack.   Ok just order up and down and go with the flow.  The basic wheel is wider than the smaller ones.  gphil

JohnBuckner 10-08-2012 06:04 PM

RE: Bolt on axle
 
OK first thing first. You are on the right track and bigger wheels are helpfull many times. But do avoid the temptation to change an airplanes CG to make it taxi better this is always the worst thing you can do and I hear fellows who have been around awhile suggesting this to new folks.

Alway the CG is set to acheve good flight characteristics not necessarily ground handling. Now one suggestion is to simply set if you have a capable radio (almost all but the cheapest do have dual rates at least on elevator and ailerons) the high elevator for more throw to use only while you taxi.

Now back to the bigger wheels and yes Conventional gear is used in the full scale world to indicate a taildragger. What exactly do you have for main gear, is it sheet aluminium or is it piano wire. It is no problem at all to find larger wheels but we need to know the kind of axle and it likely size. In most forty sixty sized stuff it will be 5/32. If the larger sized wheel only have an 1/8 axle size then it is normal to drill it to what is neccessary.

So what kind of main gear do you have?

John

Gray Beard 10-08-2012 06:41 PM

RE: Bolt on axle
 
John, he just said his CG is good, nothing about changing it. However, bigger wheels will weigh more and change the CG. If you have bolt/screw on LG then it is simple to change the axels. Most the time it is just a mater of drilling out the center hole in the wheel to make them fit the axel. They can be drilled so they are very thin on the inside without a problem.

gphil 10-08-2012 07:09 PM

RE: Bolt on axle
 
The main gear is a dubro, fiber type, wide stance and yes went to great lengths to keep the cg correct even bought a balancer.  I am hoping that the wheels will not offset the balance that much.  Pretty good at balancing so I will just have to correct it.  Either going to be a three inch or four wheel.  I think the lesser will work.  Also going to recheck the  throws on the elevetor and set as per manual.   Thanks guys.   gphil

JohnBuckner 10-08-2012 09:01 PM

RE: Bolt on axle
 
Yes I read the gentlemans post GB and I only was suggesting "avoiding the temptation" a simple trap that messes up lots of people.

Gphil OK so now we know we are not dealing with piano wire axles/gear but the straight machined and nutted axles. Just happened to have replaced recently a new set of Dubro 4" Big Wheels (a balloon type) on my 50cc Katana and I used Dubro 1-1'4inch long by 5/32 spring steel axles. What confused things a bit was when you mentioned adjustable axles, I know of no straight nutted axle that is in some way adjustable.

At 1-1/4 if you use any spacers and or a wheel collor the the they are a little tight. Since I always solder a washer and use no collors it is a perfect length with no problems. Also the 5/32 axles are what the wheel is drilled with. If you use this wheel and I do not know if this is the 4 incher you are talking about but perhaps you would be better off going to the 3/16 X 2 inch if you intend to use wheel collors.

Now I am guessing your airplane is some sort of 40/60 sized stick and the four inchers may be overkill. And contrary to popular beleif GB and I do occassionaly agree sometimes and the four inchers are quite heavy compared to some other so indeed CG of course as any other change needs to be corrected back to your previously established position for flight. Of course as you noted you already know to do that.

I think actually the three inchers would be the ideal for you to try. Oh by the way I love Dubro big wheel balloon smoothies even though they are heavy for any given size, There're may favorites.

John


gphil 10-09-2012 04:06 AM

RE: Bolt on axle
 



Thanks John,  

I guess I expect you fellas to be physic and know all what I am talking about,,,,apologize.     What this craft is, is a trainer, Avastar, which I converted to a tail drager because I had made a yard dart out of it so many times the firewall was trashed and I did not want to do all that cutting out.   So took off the wire gear and put a a Sullivan tail wheel and a Dubro gear up front, sort of a plastic fiberglass looking wide spread gear and used the wheels off the orginal plane.  I followed all comments here and other places off t he net, bought a balancer and did her up right.  Oh and changed out the engine to a OS .46.    Once the plane gets into the air , flies beautifully with no need to use any more that hallf throttle.  Here again the old plane went forever on the ground and not fast therefore the larger engine.  It was real heavy in the nose so moved weight to the tail.  As mentioned, flies great and looks great.  I am a beginner in this and maybe have only ten solo's under my belt.  Attempting a build now on a Stick 60 which is going to be a gasser.  Keeps me out of trouble and keeps you guys gessing.   Thanks for all the info .  Going to keep stabbing at this through the winter here,,,,, Georgia,,,,, which we can.  So once more thanks and I am sure more questions are coming.   Thanks to you and this forum and Youtube.   gphil

JohnBuckner 10-09-2012 06:24 AM

RE: Bolt on axle
 
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You are welcome and no need to apologise, its just a matter of figuring things out. It does sound like you are enjoying your continuing adventure and after all thats what its all about, ya never want the learning to stop for any of us as that is when the fun stops. Thats the beauty though with this hobby/sport/passion it is so varied that there is always something else to learn;)

Just for some size perspective and giggles, here are a couple of pictures of those Dubro four inch 'big wheels' that we were discussing and they are set up on forty sized trainer. That airplane is set up for a series of Wingless Trainer Races we have run here in the past and they are all about ground handling and not so much flight. Although the rules required a proof flight with whatever gear we cobbled up for the event. With those wheels/gear the weight is a full pound heavier than the stock wire gear and wheels of about 2.5 inchs.

I am sure the sixty stick you are working on will be a pleasent surprise for you.

John

kenh3497 10-09-2012 06:51 AM

RE: Bolt on axle
 
OK John... It's all your fault! :)

My curiosity has been peaked by your landing gear on the photo of you "ground pounder". Please explain the forward cross bar.

Thanks! Ken

PS Sorry for getting off topic. But like I said it's all John's fault:D

harlanb 10-09-2012 07:11 AM

RE: Bolt on axle
 
gphil
One thing that you can try, that I dont think will be too hard to do is put a wedge under the landing gear to point the gear forward more.
you can experiment with a couple different wedge widths to find the best angle.

gphil 10-09-2012 07:53 AM

RE: Bolt on axle
 
That "wedge" is a good idea.  I tried very hard to make sue the axles lined up with the  leading edge.  Thursting them a little forward may be the answere. 

Oh and John,     Have much bench stock on the wall?   I need to visit.    lol    gphil

kwblake 10-09-2012 04:21 PM

RE: Bolt on axle
 
Hey gphil. I know this is not what you are looking for, but it may come in handy in the future. I wanted to go to larger dia. tires on my Nexstar. Being a trike, the two mainwheels were no problem, just bought larger dia. axles. The nose wheel was a different story until I came across these from Robert. Cut the vertical part of the 5/32 wire axle off and on goes one of these, bingo, 3/16 axle.

http://www.robart.com/products/532-w...apter-316-axle

JohnBuckner 10-10-2012 01:21 AM

RE: Bolt on axle
 
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Quote:

ORIGINAL: kenh3497

My curiosity has been peaked by your landing gear on the photo of you ''ground pounder''. Please explain the forward cross bar.

Thanks! Ken


Ken I did that for two reasons. The first is that gear is so long and wide track that a single strap was far to flexible and the second reason is it gave me three different but adjustable positions to increase or decreas the wheel base by up to three inchs total. For the Ground Pounder:D gear I ended up at the rearmost position which is about two inchs aft of the stock main gear. I was just barely able to rotate for the proving flight to demonstrate flight capability.

Here is a picture of my Schneider Sport that I used something similar for a differnt reason and it is related to this discussion. The purpose in doing this (agine gave me three possible axle positions aft of where this gear was first placed. This airplane is of course a seaplane and the wheeled gear is only a non scale like after thought. It was too far forward and this made the airplane a hopeless Boinger. Ya know like boing, boing boing on landings. At the rearmost position the ship mellowed out beautifully.

When converting an airplane like GP has the for and aft position of the main gears footprint in relation to the airplane CG is very important. Thing to look for if the gear is too far forward: the airplane will be more directionally unstable during takeoff and landing. In addition it will be difficult to do touchdown without bouncing (a Boinger) .

When the gear has been placed more to the rear The directional stability will be much improved and the bouncing tendencys during landings will become benign but the airplane will nose over easily especially if good elevator technique is not used during taxi. Actually the very best ground handling and landing behavior is when the mains are exactly at the CG as was the practice of some late forties gliders. Of course the problem with that is its darn hard to keep the propellor from hitting the ground if ya got one.

John

gphil 10-10-2012 04:06 AM

RE: Bolt on axle
 
I have the same main gear on my plane and thought of that same configeration you have but really did not see how to do it.  Brilliant for sure thanks fella.  I knew there must be some difference in the axle dia. actually thought maybe one was misspacked so to speak.  Got a huge stock of parts now .   lol   gphil

gphil 10-10-2012 06:07 AM

RE: Bolt on axle
 
   


            By the way John,    One   SWEET  plane.   Hope someday to be able to keep one of those in the air.   gphil

JohnBuckner 10-10-2012 08:52 AM

RE: Bolt on axle
 
1 Attachment(s)

Quote:

ORIGINAL: gphil




By the way John, One SWEET plane. Hope someday to be able to keep one of those in the air. gphil




Thank you GP. This is the way it normally looks. But more important I have no doubt you will progress nicely, you are dotting all the right I's and crossing the T's. You will no doubt realize the dream ;)

John

aspeed 10-10-2012 07:12 PM

RE: Bolt on axle
 
Yes, like John said, you can move the landing gear forward a bit  to stop noseovers.  If you go too far it will have worse ground handling but protect the prop.  Some older (very old) planes had the wheels ahead of the prop to protect it.  Around the leading edge of the wing is pretty much normal now.  Also longer gear can cause noseovers.

gphil 10-10-2012 07:25 PM

RE: Bolt on axle
 


   That gear is a little tall.  I do have another that is a little shorter.   Got plenty of avenues to explore thanks to all the comments.   gphl</p>


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