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Tire pressure monitor



 
 
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  #21  
Old August 16th 19, 05:12 AM posted to rec.aviation.soaring
Eric Greenwell[_4_]
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Posts: 1,939
Default Tire pressure monitor

Steve Koerner wrote on 8/15/2019 4:59 PM:
As it turns out, I just recently addressed this issue for the JS3 tailwheel.. The retractable tailwheel is quite small. The air volume is such that any attempt to put a gauge on it will drop the pressure quit a lot. Also being so small, I found it hard to judge by eye.

The method I came up with uses a machinist outside caliper to measure tire bulge. It's easily understood with these pictures:

https://photos.app.goo.gl/uyt8BgJWRSKKHuj6A

There's a certain skill required to use the machinist caliper -- the key is zero spring pressure. Accuracy is about 5 PSI.

I was able to accomplish the calibration without any reference to dimensional measurements (inches or mm).

Since this was just devised a couple weeks before the OP came on with his question, it hasn't had much field testing. We'll see if this is a good solution after I've used it awhile.


Clever! But, are there solid tire wheels that could replace the pneumatic one? Or
get it filled with foam?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...anes-2014A.pdf
  #22  
Old August 16th 19, 05:09 PM posted to rec.aviation.soaring
Steve Koerner
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Posts: 430
Default Tire pressure monitor


Clever! But, are there solid tire wheels that could replace the pneumatic one? Or
get it filled with foam?


I know some owners have talked about having the tailwheel foamed. I don't really know if foam is good enough or not. A key function of the tailwheel tire is to protect the structure against hard impacts. Spring and damping dynamics of foamed tires certainly differ from air. I'm willing to make little design deviations like that only when I'm personally very sure that there won't be adverse consequences.
  #23  
Old August 16th 19, 05:35 PM posted to rec.aviation.soaring
Bob Kuykendall
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Posts: 1,345
Default Tire pressure monitor

On Thursday, August 15, 2019 at 4:59:03 PM UTC-7, Steve Koerner wrote:
The air volume is such that any attempt to put a gauge on it will drop the pressure quit a lot.


One of the best real-world application of the Observer Effect I've heard of in a while.

--Bob K.
  #24  
Old August 16th 19, 06:01 PM posted to rec.aviation.soaring
Dan Marotta
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Posts: 4,601
Default Tire pressure monitor

Another application of Heisenberg's Uncertainty Principle.

On 8/16/2019 10:35 AM, Bob Kuykendall wrote:
On Thursday, August 15, 2019 at 4:59:03 PM UTC-7, Steve Koerner wrote:
The air volume is such that any attempt to put a gauge on it will drop the pressure quit a lot.

One of the best real-world application of the Observer Effect I've heard of in a while.

--Bob K.


--
Dan, 5J
  #25  
Old August 16th 19, 09:15 PM posted to rec.aviation.soaring
Eric Greenwell[_4_]
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Posts: 1,939
Default Tire pressure monitor

Steve Koerner wrote on 8/16/2019 9:09 AM:

Clever! But, are there solid tire wheels that could replace the pneumatic one? Or
get it filled with foam?


I know some owners have talked about having the tailwheel foamed. I don't really know if foam is good enough or not. A key function of the tailwheel tire is to protect the structure against hard impacts. Spring and damping dynamics of foamed tires certainly differ from air. I'm willing to make little design deviations like that only when I'm personally very sure that there won't be adverse consequences.


A flat tail wheel has different dynamics, too :^)

Perhaps the tail mount is designed to absorb the energy and crumple before the
structure? I'd contact the factory with a list of substitutes (foamed, solid
rubber/urethane, etc) you'd like use, and get their blessing. I suggest a
polyurethane scooter wheel, which are available in several sizes, and work well
with the ASH 26 E steerable tail wheel, based on the owners' group experience:
strong and good shock absorbing.


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...anes-2014A.pdf
  #26  
Old August 16th 19, 11:43 PM posted to rec.aviation.soaring
Steve Koerner
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Posts: 430
Default Tire pressure monitor

On Friday, August 16, 2019 at 1:15:10 PM UTC-7, Eric Greenwell wrote:
Steve Koerner wrote on 8/16/2019 9:09 AM:

Clever! But, are there solid tire wheels that could replace the pneumatic one? Or
get it filled with foam?


I know some owners have talked about having the tailwheel foamed. I don't really know if foam is good enough or not. A key function of the tailwheel tire is to protect the structure against hard impacts. Spring and damping dynamics of foamed tires certainly differ from air. I'm willing to make little design deviations like that only when I'm personally very sure that there won't be adverse consequences.


A flat tail wheel has different dynamics, too :^)

Perhaps the tail mount is designed to absorb the energy and crumple before the
structure? I'd contact the factory with a list of substitutes (foamed, solid
rubber/urethane, etc) you'd like use, and get their blessing. I suggest a
polyurethane scooter wheel, which are available in several sizes, and work well
with the ASH 26 E steerable tail wheel, based on the owners' group experience:
strong and good shock absorbing.


Eric, Quite sure the factory isn't interested in blessing a chinese scooter wheel when the design presently calls for an aircraft wheel with aircraft tire. Anyway, there's no actual problem with the present wheel that I know of, so I haven't a motive for pursuing an alternative. The challenge of measuring air pressure is a small matter and hopefully I've got that put to bed.
 




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