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  #121  
Old 09-28-2010, 12:31 PM
Mike Macon Mike Macon is offline
 
Join Date: Feb 2006
Location: Sisters, OR
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Default Holding up nose wheel while braking

Quote:
t a good thing to hold up the nose wheel as long as possible but if your landing on a short grass strip you want to get on the brakes as soon as possible the nose whell comes down as soon as you apply brakes at any speed
You can brake while holding up the nose wheel. It is just a matter of applying more back pressure on the stick as you apply braking pressure. It is a balancing act but very doable.
This was one of the things I practiced with Seager during transition training and emphasized during a recent flight with him while landing on Vernonia's grass strip. It also helps in safely shortening the landing rollout on any surface.
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  #122  
Old 09-28-2010, 01:53 PM
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Av8torTom Av8torTom is offline
 
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Default Well good point, but...

Quote:
Originally Posted by Kiwi View Post
By far the best solution is an oleo gear.

Works well as you can see in this video: http://www.youtube.com/watch?v=_lO3n...eature=related

Redesigning the existing rod is just shifting the deck chairs around on the titanic. Someone suggested the 152 unit; good idea, the aeroplane weight is in the ball park. Surely a non-certified copy of that is the way to go and won't cost too much. The 152 unit mounts on the engine mount, so there is a good basis for reverse engineering, as opposed to the 172 unit which is mounted on the firewall.

A bonus will be that it is steerable.

Once that's sorted out, we can then move onto the mains and come up with a better system there too.

Cheers,
Andrew.
Even oleo struts nose struts can fail
http://www.youtube.com/watch?v=NMmHYWjEmkY
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  #123  
Old 09-28-2010, 01:56 PM
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Brantel Brantel is offline
 
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Default

Hmmm,

Not sure I would classify that torture to be a failure.
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  #124  
Old 09-28-2010, 02:04 PM
PCHunt PCHunt is offline
 
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Default

Oleo stut failed after torture, but aircraft didn't "flip".
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  #125  
Old 09-28-2010, 02:33 PM
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Av8torTom Av8torTom is offline
 
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Default Indeed

Quote:
Originally Posted by PCHunt View Post
Oleo stut failed after torture, but aircraft didn't "flip".
mmhummmmm - good point... but it was also on tarmac.
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  #126  
Old 09-28-2010, 05:47 PM
David Paule David Paule is offline
 
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Default

Quote:
Originally Posted by Av8torTom View Post
It's been said before by many, and I completely agree. A larger nose wheel would be a huge improvement in the design, and less expensive than a re-do of the nose gear. It would minimize the effects of surface imperfections and raise the "nut" even further off the ground. This may also require larger main wheels, but that's been done by others as well.

When I look at that YouTube vid of the nosewheel on the grass, I can easily visualize a larger nose wheel riding more smoothly over the surface.

My $0.02
A larger nosewheel, and the larger fork needed to clear it, will lower the natural frequency of the existing strut. That could increase the deflection....
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  #127  
Old 09-28-2010, 07:12 PM
chunt0 chunt0 is offline
 
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Location: Canton, MI
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Default

A larger nose wheel also raises the center of gravity-tradeoffs, tradeoffs.
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  #128  
Old 09-28-2010, 07:50 PM
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Av8torTom Av8torTom is offline
 
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Default Yes, but...

I would be surprised if the small increase (1-2 inches) in CG would make much difference.
I think this guy has done some serious thinking about this:

http://mesawood.info/myrv7a/building...armodinfo.html
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  #129  
Old 09-28-2010, 08:53 PM
PaigeHoffart PaigeHoffart is offline
 
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Default 8A vs 7A

Quote:
Originally Posted by JCFL View Post
I did a brief search and did not find any mention of 8A's experiencing this kind of nose gear failure. Does anyone know of any? I realize there are far fewer 8A's than 6A's or 7A's flying but am curious because the 8A can be very nose heavy depending on the load.
If you read this:
http://www.ntsb.gov/publictn/2006/RV_Study.pdf
It sounds like every A model has been involved.

Having said that, there might be a reason why we don't hear about 8A nose overs as much. Looking at the 3-view drawings on Van's website gives me the impression that the 8A has a slightly greater distance between the nose wheel and mains than the 7A. It looks like about 8", but it would be interesting to measure. A nose wheel farther away from the CG might reduce some of the loading.

Looking at Van's published weight on nose wheel chart seems to confirm this. For the same weight and CG location, an 8A has about a 7% lower nose wheel weight when compared to a 7A. Perhaps the combination of slightly lower static and dynamic loading is significant?

Paige
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  #130  
Old 09-29-2010, 10:09 AM
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RV7AV8R RV7AV8R is offline
 
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Default

Quote:
Originally Posted by PaigeHoffart View Post
If you read this:
http://www.ntsb.gov/publictn/2006/RV_Study.pdf
It sounds like every A model has been involved.

Having said that, there might be a reason why we don't hear about 8A nose overs as much. Looking at the 3-view drawings on Van's website gives me the impression that the 8A has a slightly greater distance between the nose wheel and mains than the 7A. It looks like about 8", but it would be interesting to measure. A nose wheel farther away from the CG might reduce some of the loading.

Looking at Van's published weight on nose wheel chart seems to confirm this. For the same weight and CG location, an 8A has about a 7% lower nose wheel weight when compared to a 7A. Perhaps the combination of slightly lower static and dynamic loading is significant?

Paige
When you compare these photos of planes with a similar nose gear but two without the problem there are other differences as well. Gruman and DA40 have wider lower stances. Just looking at these photos, which looks more unstable?
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