I would like to see a stronger fork with more clearance to tire crown.
Please keep us all up to date on this............. Many will be ready with check book.
Mick, This looks great. Zooming in on the nose fork, I would like to see a stronger fork with more clearance to tire crown. I would like to see how you got the stiffness needed with only one attachment location.
Please keep us all up to date on this............. Many will be ready with check book.
What about carburated engines? Will the gear clear the airbox?
For this reason I have had the fork assembly made so it can be changed if needed. Time will tell if I need to make a thicker fork and give more clearance. When I drilled the axle bolt hole I new straight away that more clearance would be nice.
The nose gear is mounted using the original gear socket to take the aircraft weight as per the original. An additional attachment is made to prevent twisting and is located at the gear socket gussets, the gussets are strengthened with 4130 and is attached with bolts. Due to the exhaust location no diagonal bracing is fitted at this time but would be possible to fit if required. At this point there appears no side wise movement of the gear leg.
My theory is that the gear, should it fail, will not cause a roll over. So it has been designed that if it should fail it would be a twisting failure of the gear leg and the aircraft will slide rather than go over. I personally would rather a new engine and prop than a new complete plane.
I will post more on the testing once I sort out the steering linkages.
Mick
Looking forward to seeing how you design the fairings.
Also wondering how you check the failure mode of the gear.......
Hope it all works out nicely!
I think that I would install a hitch receiver on the front of my 72 f-250 and mount the strut as if it were on the A/C. Then drive it out across the field with cameras mounted on the bumper to see how it does.
For steering, look under the hood of a Piper Warrior.
To make this a nice system, The mains should be shortened so the A/C squats like the 6A. This would make it easier to enter the A/C and allow the nose wheel to float better.
I final fitted my new nose gear to my 7A. I had it Custom made and needed no modification to the motor mount. Hope to finish the steering linkages this week and begin taxi tests. The weight is only 4-5 Lbs more than the original gear.
Mick Haynes
Australia
Like most of the above posts, I am also very glad to see this new nose gear. Devising a realistic test program will be quite challenging. A great resource on design and testing is Pazmany's book "Landing Gear Design for Light Aircraft".
As a starting point see FAR 23.499 for design loads:
Supplementary conditions for nose wheels.
In determining the ground loads on nose wheels and affected supporting structures, and assuming that the shock absorbers and tires are in their static positions, the following conditions must be met:
(a) For aft loads, the limit force components at the axle must be--
(1) A vertical component of 2.25 times the static load on the wheel; and
(2) A drag component of 0.8 times the vertical load.
(b) For forward loads, the limit force components at the axle must be--
(1) A vertical component of 2.25 times the static load on the wheel; and
(2) A forward component of 0.4 times the vertical load.
(c) For side loads, the limit force components at ground contact must be--
(1) A vertical component of 2.25 times the static load on the wheel; and
(2) A side component of 0.7 times the vertical load.
[(d) For airplanes with a steerable nose wheel that is controlled by hydraulic or other power, at design takeoff weight with the nose wheel in any steerable position, the application of 1.33 times the full steering torque combined with a vertical reaction equal to 1.33 times the maximum static reaction on the nose gear must be assumed. However, if a torque limiting device is installed, the steering torque can be reduced to the maximum value allowed by that device.
(e) For airplanes with a steerable nose wheel that has a direct mechanical connection to the rudder pedals, the mechanism must be designed to withstand the steering torque for the maximum pilot forces specified in Sec. 23.397(b).]
Regarding testing see:
FAR 23.723 Shock absorption tests.
(a) It must be shown that the limit load factors selected for design in accordance with Sec. 23.473 for takeoff and landing weights, respectively, will not be exceeded. This must be shown by energy absorption tests except that analysis based on tests conducted on a landing gear system with identical energy absorption characteristics may be used for increases in previously approved takeoff and landing weights.
(b) The landing gear may not fail, but may yield, in a test showing its [reserve] energy absorption capacity, simulating a descent velocity of 1.2 times the limit descent velocity, assuming wing lift equal to the weight of the airplane.
Section 23.725 prescribes the Limit Drop Test.
So compliance with the FARS seems to be limited to design calculations validated by a drop test.
BTW, the use of a '72 F-250 is not referenced anywhere in the FARs
On the other hand a towing rig that simulates the weight of the aircraft and can be driven across a series of "bumps" should be helpful in determining the robustness of the nose gear. The difficulty in this approach is determining the size of the "bump" or "hollow". I read that when the Piper Tri-Pacer was being designed, the Piper engineers towed their test rig across a ploughed field This certainly represents a "worst case scenario" but it may not be realistic for the RV series.
I had a load test done on the original gear by a qualified aeronautical engineer when I designed long range leading edge tanks for the RV7. The tanks were designed to FAR23 standard and pasted with a good safety margin, the landing gear on the other hand !!. Even before the test was conducted the engineer correctly announced it would fail. (We did not conduct a drop test but a static load test).
Just thinking out loud - I like the idea of the new nose gear although I wasn't wild about the steering. Seems that it would be overly complex. Just the new nose gear would generate a lot of interest!
The small frontal area of the RV leaves things more cramped for space compared to Pipers and other AC. Maybe some type of bellcrank setup in the cockpit linking the L and R pedals in the center would be viable and would not need as much space FWF. A spring damper (Piper) in the steering linkage would help reduce stresses on the steering system.
Good luck with your development.
Roberta
It seems there is always a solution for one problem but it then causes another problem some where else.
Mick
Thank's for all the encouragement guys, I know there is a solution, its just finding the best way of accomplishing it. Once done I'm sure there will be someone who will have other ideas on how it should have been done, but we need to start somewhere. Flight safety ( A magazine here in Aus ) Has listed three RV accidents last month. One was engine failure, but the other two caught my attention as they were both A models with nose gear collapses. I thinks we have a problem!!
I just got home from the hanger, not good signs when bridges are closed and some parts of the roads are under water! Any way checked the strip and I don't think there will be any action on the runway for a few days. The ground is sodden with water and we will need about a week of dry weather before I'll be able to drive on it.
Cheers
Mick
Glad to see such innovative thinking...
Thinking out loud here - what about a servo controlled steering? Too complicated?
T.