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Nose Gear Fork Tension

K

keny

Member
Hello, All, I've tightened the nose gear fork's nut, with U-611 washers facing one another, to 26 lbs and can barely move the the fork by hand. I'm using a fish scale that is probably accurate within a few pounds. I realize we don't have a shimmy dampener in the design but 26 lbs. seems excessive. Van's tech support told me I just have "to believe". I'm ready to be surprised. For those of you flying, what has been your experience with this? Thanks, Ken
 
Just make sure it's lbs, not kg's. That has been tried before too, but was probably a fraction too much. :D
 
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I'm thinking the same thing, and using a very accurate digital fish scale. But, as I have been told by friends already flying their 12's, I will just need to 'believe' :D

I like to think I'm a fairly strong guy, but when I can barely turn the darned thing by hand, off the nose gear, it makes a fella wonder how in the heck it will ever caster. :(
 
You are fine. Don't go any less torque or you will get a real surprise. Saying that, be sure you check tightness at least at every 50 hours or so and run tire at max pressure.
 
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woodmanrog said:
You are fine. Don't go any less torque or you will get a real surprise. Saying that, be sure you check tightness at least at every 50 hours or so and run tire at max pressure.
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BTW, the latest plans revision 35-02 rev 3 (11-30-12), Step 5 reduced the recommended nosewheel tyre presssure from 28psi to 22 psi.
 
I don't want to start an argument but my lamb tire on the front has a max pressure rating of 70lbs. It would seem that if you were to run at anything under 30 lbs, you would be really running underinflated. I had an incident where an underinflated nosewheel tire tore up a wheelpant when it flexed. That is why I run at max pressure. Maybe someone else can chime in with some thoughts.
 
woodmanrog said:
I don't want to start an argument but my lamb tire on the front has a max pressure rating of 70lbs. It would seem that if you were to run at anything under 30 lbs, you would be really running underinflated. I had an incident where an underinflated nosewheel tire tore up a wheelpant when it flexed. That is why I run at max pressure. Maybe someone else can chime in with some thoughts.
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This discussion is in the RV-12 forum.
Totally different airplane from the other RV's.
It uses a 5.00X5 nose tire and the nose gear only has a little over 100 lbs of load on it.

BTW, the pressure in the tire is dynamically part of the landing gear system. Over inflate the tire and you run the risk of causing structural damage in an unforseen incident, where none would have occurred if the tire was properly inflated.

BBTW I believe a C.N. is coming out that changes the recommended nose fork breakout force to be 18-20 lbs for improved ground steering.
 
woodmanrog said:
You are fine. Don't go any less torque or you will get a real surprise. Saying that, be sure you check tightness at least at every 50 hours or so and run tire at max pressure.
Click to expand...

Tip regarding dealing with nose wheel shimmy on RV models other than the RV-12


The higher the pressure in the nose tire, the more likely it is to shimmy.

The reason is that as pressure goes up, the size of the tire contact patch on the ground surface goes down. The bigger the contact patch, the higher the rotational/pivot friction between the tire,
The higher the rotational/pivot friction, the less likely that shimmy will occur (but still requires proper adjustment of nose fork friction drag).
 
keny said:
Hello, All, I've tightened the nose gear fork's nut, with U-611 washers facing one another, to 26 lbs and can barely move the the fork by hand. I'm using a fish scale that is probably accurate within a few pounds. I realize we don't have a shimmy dampener in the design but 26 lbs. seems excessive. Van's tech support told me I just have "to believe". I'm ready to be surprised. For those of you flying, what has been your experience with this? Thanks, Ken
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Ken,

I can only relate my own experience. Others have had different experiences. During construction I followed the plans and set the tension to 26 pounds. During early taxi tests and flights I spent a lot of time stomping on the brakes to make the airplane turn. Control was very difficult and imprecise. I readjusted the tension by trial and error until control was easy with moderate brake application. I don't know what the tension is now. I think setting tension with the fish scale is only good for setting a starting point, and a realistic final tension value can only be determined by trial and error. I have found it beneficial to remove, clean, and lubricate the washers once a year.

I maintain recommended tire pressure, and have had no problems with shimmy. If I did experience a shimmy, I would increase tension one flat of the nut at a time until cured.

JMHO!

John
 
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RVBUILDER2002 -- Did Van's ever come out with a C.N decreasing the tension on the nose wheel strut pivot nut from 26# down to ??? I am about to drill the cotter pin hole and would like the latest info. Thanks! -- David
 
DHeal said:
Did Van's ever come out with a C.N decreasing the tension on the nose wheel strut pivot nut from 26# down to ???
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I have not seen anything, but I dropped the tire pressure to 20psi and set the break out force at 20 and it works good. No shimmy and easier to maneuver.
 
Has anyone actually experienced a significant shimmy on landing and can tell the tale?

I'm just curious....

Erik
 
nose wheel questions

recent rv 1c factory built elsa calls for 22 lbs on nose tire and i believe 20lbs torque on catering nose wheel is this correct? i have to really stomp on the brakes when i asm taxiing slowly to effect turns and the wheel feels pretty easy when i hand turn it (lifted off the ground) could i be too loose???
 
Ditto..

Ken,
I had the same experence as Big John. Follow his instructions and you will be OK. I had to do the same thing on my RV-6A.
 
I just did this step yesterday. The new tension in the most current version of the finish kit plans has the fork tension at 18-20 lbs. The nose tire pressure at 22 lbs and main tire pressure at 28 lbs.
 
If you have to stomp on the brake to steer you may need to precondition the brake pads. They are pretty wimpy until you do the series of stop and goes recommended by MATCO. Mine has been at 26# for two years with no shimmy or steering issues.
 
Nose Gear Fork Tension on the -12...

jsenft said:
I just did this step yesterday. The new tension in the most current version of the finish kit plans has the fork tension at 18-20 lbs. The nose tire pressure at 22 lbs and main tire pressure at 28 lbs.
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RFSchaller said:
If you have to stomp on the brake to steer you may need to precondition the brake pads. They are pretty wimpy until you do the series of stop and goes recommended by MATCO. Mine has been at 26# for two years with no shimmy or steering issues.
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As second owner, I am conducting my first condition inspection. I've had no steering issues with my current nose wheel installation. I will have to drill the fork to relocate the cotter pin hole to obtain the 18-20 lbs fork tension. Is this really necessary to do? My inclination is to live with what I already have.

Regards,
 
If you're happy with it why change? There is no Vans notification to change the old ones as far as I can see on their website. I assume that if 26# was causing an issue they would have notified us all rather than just changing the pull force on later builds.
 
TomVal said:
As second owner, I am conducting my first condition inspection. I've had no steering issues with my current nose wheel installation. I will have to drill the fork to relocate the cotter pin hole to obtain the 18-20 lbs fork tension. Is this really necessary to do? My inclination is to live with what I already have.

Regards,
Click to expand...

I am curious why you have to drill the fork to lessen the tension?
 
As second owner, I am conducting my first condition inspection. I've had no steering issues with my current nose wheel installation. I will have to drill the fork to relocate the cotter pin hole to obtain the 18-20 lbs fork tension. Is this really necessary to do? My inclination is to live with what I already have.
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If you are happy with nose wheel steering and it does not shimmy, then do not mess with it. Do not drill a new cotter pin hole. If necessary, a thin washer can be added under a castle nut to make the holes line up for the cotter pin.
Joe Gores
 
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