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Written on: 29 August 2009 [07:18]
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richar18
Topic creator
registered since: 29.08.2009
Posts: 4
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What do you guys think of self inflating tire technology, and what would it take for you to buy a device (assuming it existed) for each of your tires?
There are a few technologies in the works, one that integrates directly into the tire itself (very cool, but you have to pay more for a tire), and one that mounts to the hub (but you have to drill into your rim - or would this be a big deal?).
In case you are curious, I am also working on a self-inflating tire technology - I am a grad student (which is why I am on this forum on a Friday night  ) and am in proof of concept stage right now. The device would be small - about 1" x .6" x 1.5", or a little smaller than most Tire pressure Monitor System (TPMS) sensors, and could fit on the end of a valve stem like a TPMS sensor. The cost would be under $100 total for all 4 tires, likely including installation at a commercial tire shop. It would pump enough air at typical speeds to keep your tires from going flat if you ran over a nail, or other sharp object that causes only fixeable tire damage. It uses no batteries, and only pumps at over about 25 mph.
What do you guys think (assuming it works  )?
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Written on: 29 August 2009 [11:29]
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insight
registered since: 26.04.2008
Posts: 33
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richar18....what happens when you park and not knowing you've had a puncture you return to the car and find a flat tire? 
Even the safety aspect is doubtful since not all punctures are slow leak types.
Anything that size/weight ( about 1" x .6" x 1.5",) would be hell to counter balance and certainly couldn't be mounted on the valve stem without damaging it from centrifugal force's.
Drilling into an alloy wheel is not recomended as it compromises the structural integrity.
Of course your goal may only be to maintain a set pressure for economy running (less rolling resistance) which would make more sense than the safety aspect.
There are run flat tires on the market already to fill the safety concern.
[This article was edited 1 times, at last 29.08.2009 at 11:40.]
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Written on: 29 August 2009 [12:53]
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iamian
registered since: 23.02.2009
Posts: 105
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What powers the device?
2000 MT Honda Insight
MIMA & FAS equipped ... PHEV in progress.
Franken E-Bike 36V NiMH 600W Hub-Motor.
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Written on: 29 August 2009 [19:29]
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richar18
Topic creator
registered since: 29.08.2009
Posts: 4
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Thanks for the input guys.
Insight - the device is the same size and weight as most existing valve-stem mounted Tire Pressure Monitor sensors, which are proven safe and reliable (most MY2008 vehicle has this type of TPMS sensor). Counterbalancing will be business as usual. The correct size balance weight can be included in the package as well, which would make it easier for the installer.
"What happens when you park and not knowing you've had a puncture you return to the car and find a flat tire?"
That is a good point - and an issue this device likely won't be able to solve by itself, unless it is integrated with a TPMS sensor. This is he next phase of development. Since the device is able to generate electrical power while functioning, and is of small size and weight, the power generation/pumping mechanism should be able to replace the TPMS battery. This, while providing full tire pressure maintenance and "pump on the go." TPMS batteries are the most expensive part of the TPMS sensor, and will cost nearly as much as the power generation/pumping element of this device. Therefore, a TPMS with integrated power generation and pumping could be mfg'd for only a little more than the cost of an existing TPMS sensor.
This brings up an interesting thought regarding product line - sounds like it may be a good idea to create a much smaller system that can be mounted on the valve stem outside of the tire (instead of inside the tire) for those who don't want to pay the cost of a full TPMS, and those who want the full system would buy a more powerful version with integrated TPMS. The more powerful version would benefit from the ability to keep the wheel inflated if a fixeable puncture occurs, whereas those who purchase the cheaper smaller version are paying to keep their tires at a constant pressure year round. Would probably sell like hotcakes in cold regions  .
"Even the safety aspect is doubtful since not all punctures are slow leak types."
According to another self-inflating tire company, "For more than 90% of flat tires, it takes more than one hour since the puncture to get completely flat."
This means that a system which pumps in enough air to counteract 90% of leaks will prevent 90% of blowouts (which are caused when a tire gets low enough to start generating excess heat, which then causes the tire to fail). Run-flat tires will also accomplish this; HOWEVER - they are very costly to repair, wear more quickly than normal tires, and very costly to replace (there have been several class action lawsuits against run-flat tire mfg's).
And iamian - the device is powered by the movement of the wheel. Can't say any more than that .
[This article was edited 2 times, at last 29.08.2009 at 19:33.]
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Written on: 29 August 2009 [23:43]
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iamian
registered since: 23.02.2009
Posts: 105
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richar18 wrote:
And iamian - the device is powered by the movement of the wheel. Can't say any more than that .
How much parasitic power effects does it have?
Any effort to remove energy from the wheel is creating drag of one form or another... rotational drag, aerodynamic drag , etc.
The amount of work you can do to pump air into a tire will be limited by your efficiency and the amount of parasitic power consumption.
Depending on how much the device pulls ... people may not want the power / energy loss.
2000 MT Honda Insight
MIMA & FAS equipped ... PHEV in progress.
Franken E-Bike 36V NiMH 600W Hub-Motor.
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Written on: 30 August 2009 [22:48]
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insight
registered since: 26.04.2008
Posts: 33
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What precautions will be in place to prevent theft of these devices?
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Written on: 31 August 2009 [10:35]
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richar18
Topic creator
registered since: 29.08.2009
Posts: 4
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The device will draw about 3 watts of power per wheel at 55mph.
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Written on: 05 September 2009 [23:35]
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richar18
Topic creator
registered since: 29.08.2009
Posts: 4
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Hi Insight, sorry about the delay - missed your message.
To answer your question about theft, the device is actually attached to the valve stem INSIDE the tire (for cars). It is installed as a replacement for the original valve stem.
For motorcycles on the other hand, the device will be screwed on to the end of the valve stem. In this case, theft could be a problem; one likely solution will be to engineer the device so that a crucial piece of it is left behind if the removable part is taken off -leaving the removed part inoperable. Another solution is to provide the installer with a special tool for installation and removal. Yet a third solution would be to make the device permanent once it is installed, and to provide an auxillary valve head to inflate the tire manually if needed.
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