TFX Question for Nitro

[SchmidtMotorWorks]

Nitro,

I am interested in recording a single pulse in an exhaust pipe.

I am thinking of using a 22 cartridge in a nail gun connected to the start end of the duct.

Do you have any experience with doing this?

Do you know if the exhaust sensors can handle that kind of pulse in a duct diameter from 1" to 2"?

Would it be possible to use a signal generator to supply the tach signal, or should I rig up a variable speed motor with the tach sensor on it?

If I can do this, I would it be best to use 3 of the same sensor? As of now I have 2 intake sensors and one exhaust sensor.

Best Regards

Jon Schmidt

[nitro2]

Nitro,

I am interested in recording a single pulse in an exhaust pipe.

I am thinking of using a 22 cartridge in a nail gun connected to the start end of the duct.

Do you have any experience with doing this?

Do you know if the exhaust sensors can handle that kind of pulse in a duct diameter from 1" to 2"?

Would it be possible to use a signal generator to supply the tach signal, or should I rig up a variable speed motor with the tach sensor on it?

If I can do this, I would it be best to use 3 of the same sensor? As of now I have 2 intake sensors and one exhaust sensor.

Best Regards

Jon Schmidt

Hi Jon. We have not fired off a cartridge to create a pulse so I really have no idea what the resulting pressure and rate of pressure rise would be. Sounds interesting though. The standard pressure range port sensors we sell measure to 100 psig and will handle 200 psig without being destroyed. I'm not sure whether you have ours or a different type of port pressure sensor though. I'm guessing there are probably some ballistics studies online that indicate a ballpark pressure and rate of pressure rise, then it would just be a matter of reducing the pressure some via a chamber and duct. Reduce the pressure more than you need to start with so that the pressure sensors don't accidentally see more pressure than anticipated.

A signal generator should be fine.

[ijames]

Could you start with a cap pistol to keep the peak pressure way down for your first tests? The SAMMI maximum chamber pressure spec for .22's, short and long rifle, are just over 20,000 psi. Just from casual observation the nail gun rounds are about the same size as a .22 LR. You won't have a nail or bullet to seal the chamber initially so the peak will be much lower and the burn slower, but surely not all the way down to less than 100 psi. You could also use just a pistol primer loaded into an empty cartridge case like a .38, for something in between. Anyway, just some thoughts, I'd hate to see you blow out all your sensors on the first shot.

[Tuner]

If you have Gordon P. Blair's "Design and Simulation of Four Stroke Engines" something similar to this is discussed and diagrammed in it, however with gate or rotary valves.

[SchmidtMotorWorks]

Sounds like the 22 in a nail gun may be too powerful.

I will look into both the primer and a valve.

The valve would probably be easier, does anyone have any ideas for a valve that could open against at least 120 psi with and area at least 1" ID?

[dannobee]

Look up "quick exhaust valves." They're used in things like air horns but also in spud guns.

[Tuner]

Nitro,

I am interested in recording a single pulse in an exhaust pipe.

I am thinking of using a 22 cartridge in a nail gun connected to the start end of the duct.

Do you have any experience with doing this?

Do you know if the exhaust sensors can handle that kind of pulse in a duct diameter from 1" to 2"?

Would it be possible to use a signal generator to supply the tach signal, or should I rig up a variable speed motor with the tach sensor on it?

If I can do this, I would it be best to use 3 of the same sensor? As of now I have 2 intake sensors and one exhaust sensor.

Best Regards

Jon Schmidt

Blair single pulse in an exhaust pipe.

Copy and paste that ^^ in a web search.

[SchmidtMotorWorks]

Nitro,

I am interested in recording a single pulse in an exhaust pipe.

I am thinking of using a 22 cartridge in a nail gun connected to the start end of the duct.

Do you have any experience with doing this?

Do you know if the exhaust sensors can handle that kind of pulse in a duct diameter from 1" to 2"?

Would it be possible to use a signal generator to supply the tach signal, or should I rig up a variable speed motor with the tach sensor on it?

If I can do this, I would it be best to use 3 of the same sensor? As of now I have 2 intake sensors and one exhaust sensor.

Best Regards

Jon Schmidt

Blair single pulse in an exhaust pipe.

Copy and paste that ^^ in a web search.

Thanks.

Was there a particular link that you had in mind?

I have the book, I am interested in doing some additional tests.

[SchmidtMotorWorks]

Look up "quick exhaust valves." They're used in things like air horns but also in spud guns.

We have one of those with an electric solenoid in my kids combat robot.

The valve is about 1" Diameter and it goes up to 250 psi.
It has a light spring, I am wondering if it can close fast enough to be similar to IC engine pulse.

[SchmidtMotorWorks]

Thinking of that robot reminded me of the air tank it uses, a paint ball tank.
Maybe a paintball gun would work.

[Tuner]

I figured you would have already read Blair and would know of him as a source, just wanted to confirm. What do the punkin' chunkin' people use? There must be some big gate or ball valves those guys are using with the huge air powered launchers.

Something like this? https://www.nibco.com/Valves/Butterfly- ... ly-Valves/

[David Redszus]

Put the piston at slightly past combustion TDC (both valves closed).
Lock the flywheel in place.
Apply 120 psi via shop air to the cylinder through the spark plug.
Install electronic pressure sensors in pipe.
Connect sensors to a recording scope.
Smack the valve with a brass hammer.
View trace on scope.
Carefully note air temperature and baro.
Examine pressure trace.
Repeat as necessary to obtain consistent reading.

[Tuner]

Put the piston at slightly past combustion TDC (both valves closed).
Lock the flywheel in place.
Apply 120 psi via shop air to the cylinder through the spark plug.
Install electronic pressure sensors in pipe.
Connect sensors to a recording scope.
Smack the valve with a brass hammer.
View trace on scope.
Carefully note air temperature and baro.
Examine pressure trace.
Repeat as necessary to obtain consistent reading.

Good idea. Perhaps with piston at bottom dead center or ? for more discharge volume.

[SchmidtMotorWorks]

Put the piston at slightly past combustion TDC (both valves closed).
Lock the flywheel in place.
Apply 120 psi via shop air to the cylinder through the spark plug.
Install electronic pressure sensors in pipe.
Connect sensors to a recording scope.
Smack the valve with a brass hammer.
View trace on scope.
Carefully note air temperature and baro.
Examine pressure trace.
Repeat as necessary to obtain consistent reading.

That sounds good, although I don't want to be constrained to the bolt pattern of the exhaust face.
Also, my dyno engine is DOHC.

I can make a series of fixtures with various valves.
I think I will also use my kids paint ball tanks with a regulator and reservoir tank that they have for a hammer on a combat robot.
They have lost interest in it anyhow.

I will have to devise a consistent way to open the valve, maybe drop a weight.

[Tuner]

Maybe a tire inflator bead seater air blaster tank.

https://i.ebayimg.com/images/g/avMAAOSw ... -l1600.jpg