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dougknight

Well Known Member
Pardon if I've missed a call out on a print , or out of the builders book, but I can't recall ever seeing or reading about a clearance dimension/ reccomendation between the bottom weelpant cutout and the main tires. Nose wheel would be the same I imagine. What are most builders going with?? 1/4" to 3/8" looks about right but I may go into some gravel strips and don't want to pick up a rock that gets jammed inbetween and tears up a wheelpant. Thoughts, reccomendations and or discussion would be much appreciated.

thanks
doug
90625
N625DK
 
A good rule is that the clearance should be at least the thickness of your index finger. Less than that and a hard landing will flex the sidewalls into your wheelpant(s), causing damaged wheelpants, or maybe a wheel to lock-up.
 
Van's recommendations are 1/4" sides, 1/2" on the back.

I would consider these minimums. They should also be checked with the tires flat to ensure that there is some clearance.

Too much is better than not enough.

Vern Little
Experienced RV-9A driver (1 hr flight time in log book).
 
vlittle said:
Van's recommendations are 1/4" sides, 1/2" on the back.

I would consider these minimums. They should also be checked with the tires flat to ensure that there is some clearance.

Too much is better than not enough.

Vern Little
Experienced RV-9A driver (1 hr flight time in log book).
Click to expand...
Personally, I think Vern is right. These are a MINIMUM. I had 1/4 on the sides, and one day noticed that the tires were a little low on air, so I took the pants off. The tires were in fact a little low on air (not much) but there were wear marks on the sidewalls of the tires from the wheel pants. I opened the side gaps up to 1/2" and haven't any issues since.

Cheers
 
I would recommend at least enough roon to stick your hand up inside the wheel pant.

I mangled the left one on about the second landing on a grass strip.

Wet grass caked up enough to catch the tire to the fiberglass.

the tire won the battle.

Its embarrassing to have to walk down the runway picking up parts.

been there.

cary r
 
I have about 3/8" and 3/4" on mine and I may go a little more. I had a low tire last fall and managed to catch an edge.

Another thing:

In Van's last RVator, they mentioned the torque on the nose axle (for those of us nose dragger persuasion) was meant to secure the AL mushrooms from turning. An alternative (mentioned by Van's) to this, is to drill and stake them. I feel the torque on the axle is too high and impedes free wheeling too much. After 9 months of flying, my wheel was still too stiff to turn freely. I am going to drill and stake the mushrooms and lighten up the torque on the axle. I feel this (tight wheel) may be contributing to the nose gear problems some of us have experienced.

If you add the low tire, wheel pant clearance, the rotational force required to get the "stiff" wheel turning, less than perfect technique on touch down, and maybe a little too much touchdown speed, any number or combination of these items could spell disaster by inducing the nose gear to knuckle under.

Has anyone else experienced the nosewheel remaining too tight even after a substantial wear in period? I plan to add the stakes to my nosewheel mushrooms and reduce the torque to only enough to remove any bearing slop.

Roberta
 
caryr said:
Its embarrassing to have to walk down the runway picking up parts.
Click to expand...

BT,DT.

Even more embarrasing when Tower tells you something fell off, and to send out a crewman (me) to pick it up off the active...
 
Drill and stake?

Hey Roberta,
In a past life I was a machinist for 12 years and I'm familiar with both "drilling" and "staking". I've only recently mounted my landing gear on my -7A and I know what you're referring to as the mushrooms. Could you please shed some light on the technique you're calling "drilling and staking" for the longevity of the nose wheel assembly? Thanx a bunch!

--hawk
RV-7A (finishing)
N728E(reserved)
 
Something else to consider: re-treads are a popular replacement tire. I hear they run slightly bigger, so be generous with the clearance.
 
How I staked my front wheel bearing adapters

Here are some pictures of how I staked my mushrooms (front wheel bearing adapters).

180_8077 (Small).JPG

Installed without the wheel and tire. NOTICE the screw head WILL be covered (and retained) with the wheel pant attach bracket.

180_8089 (Small).JPG

I letter stamped the adapters so I wouldn't get them mixed up during maintenance.

180_8082 (Small).JPG

I think the part number for the screw is NAS517-3-6 is a 10-32 with a .375" grip, the grip is the same as the thickness of the fork.

I had it apart at 50 hours and found no wear or other problems.
 
Last edited:
Drill and stake

I like the idea of staking the axle of the nose wheel assembly. I have thought about doing this for some time. However I have a 6A and the system is slightly different.

The nose wheel on the 6A rotates on a 1.25 inch diameter axle PN U-609 and the axle has a 0.375 inch hole in it for the AN 6-60 axle bolt. This leaves only about 0.43 inches to drill and tap a staking bolt.

Has anyone tried to stake the axle on a 6A and what size of staking bolt did they use? Alternatively is it possible to replace the 6A axle with the 7A mushroom type axle system without changing the nose wheel fork?

Did the article in the RVator mention modifying the 6A axle system?

Unfortunately I don't subscribe to the RVator as previously when I had a subscription Vans seems to be unable to send it over to Europe on a regular basis.

Barry
 
Excellent, Tony!! I really like your idea and will use it on mine. Thanks for the post.

Barry, there was no mention of your type of axle, just the mushroom type in the newer "A" nosewheels.

Hawk, check out Tony's setup.

Roberta
 
Thanks everyone!
If the glove doesn't fit...(between the tire and pant..with my hand in it), I shall commit.( to the die grinder and sanding block). Thanks Johnny, Thanks everyone.

doug
9A
90625
N625DK
 
Wheel pant clearance

I put mine a couple of weeks ago. I used 1/2" all the way around on my 7. I'll sacrifice a knot or two for the additional safety.

Darwin N. Barrie
Chandler AZ
RV-7 N717EE
 
Nose wheel bearing drag

robertahegy said:
I have about 3/8" and 3/4" on mine and I may go a little more. I had a low tire last fall and managed to catch an edge.

Another thing:

In Van's last RVator, they mentioned the torque on the nose axle (for those of us nose dragger persuasion) was meant to secure the AL mushrooms from turning. An alternative (mentioned by Van's) to this, is to drill and stake them. I feel the torque on the axle is too high and impedes free wheeling too much. After 9 months of flying, my wheel was still too stiff to turn freely. I am going to drill and stake the mushrooms and lighten up the torque on the axle. I feel this (tight wheel) may be contributing to the nose gear problems some of us have experienced.

If you add the low tire, wheel pant clearance, the rotational force required to get the "stiff" wheel turning, less than perfect technique on touch down, and maybe a little too much touchdown speed, any number or combination of these items could spell disaster by inducing the nose gear to knuckle under.

Has anyone else experienced the nosewheel remaining too tight even after a substantial wear in period? I plan to add the stakes to my nosewheel mushrooms and reduce the torque to only enough to remove any bearing slop.

Roberta
Click to expand...
Have you staked the bearings yet and if so how is it working? What did you retorque to with the screws into the mushrooms. I have noticed mine are quite tight also, but I only have 20 hours on them. Randy-RV6A flying 3 weeks today and still smiling
 
I have not staked the mushrooms as yet. I like Tony's method and will use a variant of it when I do. My inclination is to not use a torque value, but to tighten the axle to remove any bearing slop, similar to the main wheel bearings. The torquing was done to load the mushrooms to prevent them from turning with the bearings and axle. Staking the mushrooms fixes them in place without having to overload the bearings to perform that function. This will allow the nose wheel to turn freely like the mains. This should lessen the forces on the leg and (hopefully) take a factor out of the nose gear failure equation.

JMHO

Roberta
 
just been opening up my wheelpants

On the mains I used the width of a roll of electrical tape (about 5/8ths) nudged up to the tire...

I was about to do the same to the nose but that is going to LOOK way too much gap on that little wheelpant....Did you all really use 1/2" plus on the NW or go a little smaller?

I think I might do the stake while I got it apart and extend the cap head screws for the tow bar as well.

Do RV's ever get finished?

Frank
7a...Still ready for inspection.
 
Tony Kirk said:
Here are some pictures of how I staked my mushrooms (front wheel bearing adapters).

180_8077 (Small).JPG

snipped
I think the part number for the screw is NAS517-3-6 is a 10-32 with a .375" grip, the grip is the same as the thickness of the fork.

I had it apart at 50 hours and found no wear or other problems.
Click to expand...

Tony,
I am curious as to why you drilled and countersunk the screw hole at the 12 o'clock position? It would seem to me that the 9 o'clock position left side and 3 o'clock position for the right side, would weaken the nose gear fork the least. Any position from 12 o'clock to 6 o'clock invites a stress crack to radiate out from the axle hole, through the Countersink/drilled hole, to the edge of the nose gear fork. This area has the least edge distance.
This is something to consider for those about to copy this mod. I like your idea. I was planning on doing the same thing, but at the 9 o'clock position , as viewed in your photo. I will also investigate finding a flush screw with an undersized head. The load on this screw is in shear, so screw head size is not critical. However, reducing the diameter of the countersink in the fork will reduce stress.
Charlie Kuss
 
Front axle

As well as staking the mushrooms, I made a tubular spacer to fit over the axle, between the mushrooms. I adjusted the length to give a little play in the bearings when the axle is torqued up. I think the 6a nosewheel used to use a similar system.
Steve Hill
 
I thought the same

I'm about to do this mod The problem with the 9 o clock is does the wheelpant bracket cover the screw?

Could always use weak locktite I suppose?

Frank
 
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