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New nose gear MKll

aircrafter

aircrafter

Member
Its been a few years since my last update on the new nose gear for my RV.
As happens life gets in the way and now have found time to continue with the new gear leg.
The strut has been changed to a proper Oleo strut, gone are the internal springs and scissor links. This has resulted in improved ride and is now fully tune able for compression and rebound. I also fitted a larger nose wheel with sealed ball bearings as opposed to the standard tapered bearings.
Steering has improved with no sign of shimmy and turns can still be done with the inner main wheel stationary. Several wheel fork caster angles have been tested and the one fitted has proven so far to be the strongest and most stable.
Next job is to fit a nose wheel fairing from a RV10. ( anyone have a spare or damaged one )
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Mick
 
Good work

Your nose wheel looks really nice. That large wheel should fair better over rougher ground. One of the things that Maule recommends on their nose wheel planes is to cut a small piece of rubber hose and wrap the strut to protect against chips and help prevent bottoming out of the strut. The hose is split and wrapped around the strut and held on with either clamps or in our case, several large tie wraps. Works really well.

Would love to see more pictures of your design and if you are planning on marketing it in the future.

Cj
 
Last edited:
Two questions;
What is the weight delta?
How much modification is required to the engine mount?
 
It's really just a personal project/challenge. The wife calls it the stick of steel for some reason.
As for weight, I have yet to weigh it in it's present form. Best guess would be about 5-6lbs heavier than the standard gear, mostly due to the larger wheel. After the silly season I will remove it and weigh it.
There are no mods needed to the engine mount and takes about 10 minutes to fit.
I have written to Santa for a new GoPro so hopefully I will get some video of it in action soon.
Mick
 
steerable?

Do I understand correctly that this is a fully castoring nose wheel and not a steerable nose wheel?

I'm mildly surprised that is enough castor. But great to see you continuing development.

Did you build your own oleo or adapt one from another airplane?
 
Fully castering steering.
I tested several nose wheel fork caster angles and found most wanted to fall over when turning. It does look deceptive but it has an effective 3degree caster angle.
Mick
 
Mick,
I think it looked great. I was surprised at how fast you were able to taxi over the grass and rough ground. Nice work.
 
I am curious about the new set up. Is there any snubbing in rotation?
I am wondering about the rotational wandering I see during turns. It is most clear at :15-:20 seconds. Right after you leave the parking area.
 
Right where you see that rotation is very soft sand and I suspect it is sinking slightly into the softer stuff. I have been stuck in those spots with the original Vans nose wheel. We have been in drought conditions for sometime and as you can see, no ground cover on most of the strip.
I have no external shimmy dampener but using the internal friction of the oleo. Part of the testing is weather a shimmy dampener will be required, but at this point it seems fine.
Mick
 
Mick - that looks like a pretty darned nice nose gear you've got there! You're absolutely right - to a casual observer the castor angle isn't readily visible, but from the video it's clear the castoring is working quite well.

My "flying" aircraft, a Davis DA2A, uses a similar style of steel "arch" to extend the nose gear outward and downward to the point of axel attachment. We've found there can be considerable lateral flexing with this style of gear, enough that some users (myself included) have had the fattest part of the tire rub against the inside surface of the "arch".

I'm not sure if I was seeing that sort of flexing happening in your gear when I watched your video (youtube quality limits our ability to see that level of detail). If you view the full HD video and see this type of flexing happening, it's fairly easy to add extra beef by welding a piece or two of steel tubing from the point where the oleo attaches then downward toward the axel. A good fillet of weld on the tube seems to produce the desired stiffening without adding too much weight.

Keep up the good work. This is a design I'd love to see "A" model builders have access to as an option to the stock Vans gear leg.
 
I did find the first couple of nose wheel forks flexing exactly as you describe. This one using a curve has lessened the side ways flex but there is some. No signs of rubbing but I would like it a bit stronger in side loading. Any chance you have a picture of your nose wheel fork?
Now that I'm happy with the basic design of the actual mounting and oleo, I will have a new one manufactured with a couple of weight saving changes. In a couple of weeks I should now the exact weight of the finished nose gear.
Mick
 
Nice video!

I really like this idea. The vid shows no detectable shimmy and the gear seems to track that torture-test runway surface very well indeed. Maybe you can post some video of the strut in action on a landing, especially one where the nose wheel is plopped on, or not enough flare and allowed to touch too soon. That would be the acid test.

Any tendency to shimmy on a hard-surface runway at high taxi or roll-out speeds?

Do you have a newsletter I can subscribe to?

Will you shut up and take my money? :rolleyes:

-Stormy / RV-6A
 
Bill Boyd said:
I really like this idea. The vid shows no detectable shimmy and the gear seems to track that torture-test runway surface very well indeed. Maybe you can post some video of the strut in action on a landing, especially one where the nose wheel is plopped on, or not enough flare and allowed to touch too soon. That would be the acid test.

Any tendency to shimmy on a hard-surface runway at high taxi or roll-out speeds?

Do you have a newsletter I can subscribe to?

Will you shut up and take my money? :rolleyes:

-Stormy / RV-6A
Click to expand...

Bill I'll take your money:)

Unfortunately my RV has yet to get its CofA. I'm having trouble with the fuel servo and in the video you can hear she's not running right, stumbles and missing at idle. Just another job on the list.
If anyone wants to help with testing I would be happy to discuss. Obviously someone in Aus would make it easier for logistics.
Mick
 
How Different?

Hi Mick, great looking design.
What is the difference in the wheel base dimension from center line
of front wheel to center line of the mains, old vs new?
 
Nicely done

I'm just curious. While shimmy is a common problem with free castering nose wheels, most RV-A users are more concerned with flip-overs. Do you have any reason to believe that this design will decrease this tendency?
 
Attachment at top in engine mount

Have you done anything different with how the new style gear leg is fastened into the plane?

There have been a couple instances where the bolt that holds the gear leg in the engine mount has sheared from excessive side loading/rotational forces likely due to having the swivel stop installed backward. Is your new leg design going to be applying similar sideways/rotational forces on that bolt?

Not trying to be a debbi downer at all, just wondering if some of the failures that have been seen on stock nose gear installations may find their way into this design.
 
I will try and answer the last couple of posts.

The wheel base has been kept as per original, I wanted to be able to use Vans weight and balance formula.

The design of the Vans nose gear has been discussed in detail here on the forum so I won't go into it. My gear uses an Oleo for suspension as opossed to bending so unless the gear shears or losses a nose wheel the chances of a roll over are slim.

One of the reasons for me starting on this design was the outcome from an engineer that done the loading testing for long range fuel tanks I designed. Although he had not been aware of the Vans nose gear design before seeing my aircraft, he was able to tell exactly where the failure would occur. One of his concerns was the single bolt attachment and the rotational forces applied to it.
My new gear also uses the single bolt at the top but also has a strengthening doubler mounted to the gussets of the engine mount nose gear socket. The nose gear uses a second bolt at this location to help with those rotational forces. At this point I have not seen any signs of movement at these locations.

Hope this answers your questions.

Cheers
Mick
 
Weight comparison

Vans nose gear including nose wheel, minus fairings 21Lbs
New nose gear including larger nose wheel, minus fairings 24Lbs
I should be able to shave another pound from the next gear I'm having made.
Some of you may have noticed in the video that the engine was running a bit ruff at idle and throttle up, I initially thought it was the fuel servo needing attention but turned out to be the left mag. So no more testing until that is fixed.:(

Mick
 
Castor

I like your approach.
I'm thinking of things that might arise that haven't been tested yet. Not to be negative, just to be thorough.

I'm wondering if it is possible to have the nose wheel turned a significant angle while in flight, say almost 90 degrees, by some sequence of events that I can't currently imagine.
Then, with the wheel turned 90 degrees, is there sufficient castor to make the wheel straighten out at touch-down without any other ill effects?

I could foresee the possibility of skidding the tire, or rolling the tire off the rim, or overloading the strut, if it touched down while turned 90 degrees. Generally castoring nose wheels have substantially more "trail". Or perhaps there is enough here?

I can only speculate how that could happen though, maybe. Maybe very high speed flight? Note that the aerodynamic center on the tire is about 25% of the diameter back from the leading edge, while the pivot is at 50% of the diameter. So it would be pitch unstable, and at some very large airspeed, it would diverge to 90-degree turn.
 
Hi Steve
All good points. I don't think it would be wise to fly without a wheel fairing fitted because of the points you listed. At the moment there is no steering stops fitted and I'm looking at fitting the scissor links from my previous gear. They could act as steering stops and also a form of shimmy dampening similar to some of the glasairs.
I don't think the outcome of the nose wheel being at 90 degrees during landing would be very good.

Mick
 
This design has the potential to make the A model RV much more popular. I would feel much more comfortable landing on grass or dirt strips with the A model with the larger wheel and tire plus the obvious advantage of some telescoping suspension travel.

If you do not plan to go into production of these, I hope you will be willing to pass the design on to someone who will!

It will be an added bonus if the RV10 wheel p[ant can be easily fitted.

I want one.

Randall in Sedona AZ
 
aircrafter said:
Hi Steve
All good points. I don't think it would be wise to fly without a wheel fairing fitted because of the points you listed. At the moment there is no steering stops fitted and I'm looking at fitting the scissor links from my previous gear. They could act as steering stops and also a form of shimmy dampening similar to some of the glasairs.
I don't think the outcome of the nose wheel being at 90 degrees during landing would be very good.

Mick
Click to expand...
You might also look at the Lancair Es it has the nose wheel telescoping strut, with a self centering device in the strut that centers when the nose wheel leaves the ground.
 
I did look into the Lancair strut, nice unit. The problem I felt was mounting to the engine mount and the cost.. Around $4,000 just for the strut. The total cost so far for my gear is around $2,500. A self centering cam like the Lancair and many other retractable aircraft could be fitted, but I felt the extra complexity and additional cost was not really necessary.
I'm hoping to have the magneto fixed and have the scissor links fitted next week.
Testing will continue!!

Mick
 
Scissor links fitted

The scissor links are now fitted.
The collar for the links also acts as a friction shimmy dampener and as can be seen in the new vid the wheel no longer follows the undulations at slower speeds.
The max speed according to the Dynon was 24knots for this run.
http://youtu.be/zfq-yWwCYyw
 
Nose gear MKII

Looks just like a bought one.
Well done with your persistence Mick. I guess I'll have to show it off at Oshkosh this year?
 
I am slowly increasing the speed and in the latest video you can see I was able to rotate and keep the gear clear for a short period. The steering stops have now been fitted and work well. The friction has not been reset yet so there is some wondering at very low speeds. Will reset friction before the next run.
I have noticed that there is some movement of the strut shaft fwd and aft and Although the movement does not effect the struts performance I will look at improving the internal support of the shaft to minimise any movement.
https://youtu.be/UuxKOB6eIy4
 
New A model nose gear

Over the last week I have stripped the oleo and found the shaft guide ring was not within tolerance and had allowed the shaft to move forward and aft. This resulted in wear on the shaft. A new longer guide ring has now been fitted and I'm very happy with the result, zero movement.
Tuning with oil levels and nitrogen pressures are now underway. So far I have found 7Wt fork oil and 250Psi of nitrogen gives a fairly good ride while stiffening up as the strut is compressed.
A new gear is going to be manufactured with all the changes and I will detail the build as it progresses. The engineering firm doing the work will draw up the final design and have the parts laser cut and CNC turned so it may take a couple of weeks before anything else happens.
While I have no intention of producing any other than my own I have had people ask about it, so if you are interested send my a message and I will see if we can all get a good price on the new gear.
 
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