Need measurement of clearance between RV-12's main gear wheel and the air valve stem

[John-G]

This request only pertains to RV-12 Matco main gear wheels.

I'm looking into possibly purchasing a bluetooth trike tire pressure monitoring system manufactured by FOB. Below is a link to the product.

https://my-fobo.com/Product/TRIKE2#feature

The product specifications state the sensor is .8" in diameter ... which means .4" radius from the center of the valve stem. My photos of the wheel would suggest that is just about all the clearance there is between the wheel and the valve stem .... in addition, the manufacturer also suggests an additional 1/8" of clearance.

Rather not to go through the hassle of removing my wheel pants just to take one measurement ... so I'm hoping a builder/owner of a RV-12 without wheel pants can kindly take a measurement for me

I need to know the distance from the center of the valve stem to the wheel.

[HansLab]

Hi, I jus bought these https://nl.aliexpress.com/item/33041...71184c4dCeGOEq
For the price I'll take the chance, I'll let you know if they fit or not when they've arrived.

[lon@carolon.net]

I just bought the FOBO tire pressure monitors from SlingMods.com in California (rather than the manufacturer which is located overseas). $148 plus tax for three sensors. The wheel pants are off of my plane, so the next time I go to the hangar, I'll measure the gap and let you know, or if the sensors have arrived by then, I'll tell you whether they fit. I sure hope they do, because the photos and videos I saw online made the sensors look small, so it never occurred to me that they may be too big.

[lon@carolon.net]

The FOBO tire pressure sensors I ordered from SlingMods.com arrived this morning, and I just returned from my hangar after installing them. They fit, easily.

I ordered the set of 3 sensors, and put them on all 3 gears. The 2 that I put on the mains are no where near the wheel rims. The 1 that I put on the nose gear gets close to the fork, but I rolled the plane forward and back, and the sensor does not touch the fork. Below is a link to photos, so you can see for yourself.

The FOBO phone app reports tire pressures to the tenth of a pound psi, so the system is quite sensitive. I pumped up the tires using a bicycle pump with its own attached air pressure meter, which showed pressures only to the closest 2 psi. When I installed the FOBO sensors, I got readings that were a few pounds psi too high. Rolling around on the floor of my hangar, to let a small amount of air out of the tires, and then adding back a pound or two because I had let out too much, was an activity that was funny looking enough that my wife took a photo of me doing it, but I'm not posting that one here. That one, I think, is going to our daughters and grandchildren. But it does show why many of us don't test the air pressure in our tires before every flight; crawling under the wing and fiddling with pressure meters and air pumps is a real and somewhat dirty task. It looks to me as though the FOBO sensors will make checking tire pressures easier than opening my hangar doors.

https://www.dropbox.com/sh/96n715yxy...76FBsKmBa?dl=0

[DaveWelch]

Thanks for the update Lon!

[John-G]

Lon-

Thanks ever so much for reporting back ... good to hear the FOBO sensors do fit without having clearance issues.

Guess I have an order to place.

Thanks again ... happy flying!

[Piper J3]

Let us know if you have wheel balance problems. Probably most noticeable after liftoff when wheels are spinning fast and gear is unsprung. Pressure sensors may need lead balance weights. Small wheels spin really fast...

[rcarsey]

sounds like i should build you a Bluetooth to serial converter so you can feed the data direct to your EIS

[lon@carolon.net]

Originally Posted by Piper J3

Let us know if you have wheel balance problems. Probably most noticeable after liftoff when wheels are spinning fast and gear is unsprung. Pressure sensors may need lead balance weights. Small wheels spin really fast...

Good thought. When I was shopping for pressure sensors, a question about the effect of FOBO sensors on wheel balancing was asked on a motorcycle forum. The response was "No effect," from a motorcycle rider. But a motorcycle wheel has a much larger diameter than an RV-12 wheel, so I kept your question in mind when I flew today. I didn't feel any change at all during taxi, takeoff, flight, landing or roll-out. The sensors are quite small and light. They look like tire stem caps with plastic caps on their heads. I thought the sensors might trigger a too-high-pressure alarm on the iPhone app when I landed, because I suspected that the weight of a landing plane would momentarily increase the tires' air pressures. But no alarm went off (perhaps because my landing was as smooth as butter?) Given how reluctant I was to crawl under the wings to check tire pressure the regular way, and given how important it is to check tire pressure, I'm quite satisfied with my investment in the sensors.

[John-G]

Just as a follow up - A few days ago I installed the FOBO tire pressure monitoring system for trikes ... easy install and the FOBO App was also quite easy to configure. The system seems to work great!

However, I did run into a clearance issue. It was previously reported that the FOBO sensor cleared the nose wheel fork just fine .... I suspect that is true if the nose wheel fork is the original WD-1230 fork and not the new WD-01230-1 nose wheel fork with associated bracket for mounting the wheel pants.

My RV-12 has the new WD-01230-1 nose wheel fork and associated U-00006E-L-1 mounting bracket for the wheel pants ... after installing the FOBO sensor, discovered a clearance issue with the FOBO sensor hitting the aftmost two rivets that secure the U-00006E-L-1 mounting bracket to the nose wheel fork.

See post #19 in the following thread for a link to the complete write-up about the clearance issue and my solution, plus related photos.
https://vansairforce.net/community/s...d.php?t=183562