Tire pressure monitor

On Wednesday, August 14, 2019 at 1:45:05 AM UTC-7, Phil King wrote:

This is a time consuming process - find pressure gauge...

Any sort of thing you add to the valve stem increases complexity and potential failure points and reduces reliability. In some situations that approach pays off. I think this is not one of them.

My advice: Fill the tire with an air chuck that has a gauge at the beginning of the season, while the glider is standing on it. When you do that, look at how much it bulges at the bottom. As long as the tire looks about like it did when you filled it, it probably is about right.

--Bob K.

On Wednesday, August 14, 2019 at 7:39:56 PM UTC+3, Bob Kuykendall wrote:

My advice: Fill the tire with an air chuck that has a gauge at the beginning of the season, while the glider is standing on it. When you do that, look at how much it bulges at the bottom. As long as the tire looks about like it did when you filled it, it probably is about right.

--Bob K.

This is what most probably would do (me included). However, it's impossible to see if you have pressure little bit on low side. Flight manual tire pressure is not maximum number, it is THE recommended pressure. Tube chafes with tire if pressure is short of this. Enough pressure and you really do not suffer from flat tires, at least that is my experience.

Lessons what I have learned: Never check the tyre pressure on the way to a
competition grid. Pump if obviously low and dangerous but otherwise leave
well alone.

In 2005 I did check the pressure at the 15s. Tyre went down and could not
be re-inflated as valve was jammed. Valve could not be replaced. Had to
replace the entire wheel. Got to the start, landed out in a penalty zone
took 500 point penalty. Altogether a bad day!

Jim

"If it ain't broke, fix it until it is."

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.

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

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.

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

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.

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