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Received two of these Allen Air 3×18 LF units from eBay Tuesday.

I got around to testing one of them last night and there is a lot of air leakage under 50 PSI.  I wrote Allen Air’s engineers and they wrote back:

O-Rings have a Shelf Life of about 15 years. In a cylinder it could be less due to compression set. The O-Ring will flattens out on the O.D and the I.D. This happens when the cylinder is not in use. There is a date code on the cylinder #106. The cylinder is 6 years old. All you may need is a packing kit #A3LFP (field serviceable).

I am waiting on a quote from their distributor on this “packing kit” before I return them to the eBay seller at his cost.  There is nothing else wrong with them except that they aren’t made to sit around apparently. I haven’t had this problem with Norgren or Parker products but those are for smaller bore applications anyway maybe there is a difference with the O-rings.

Two of the 3″ x 18″ actuators on the way.  Will need to figure out how to attach them over this next week.

We are exchanging the M1d for an M2d siting safety concerns with the unit if the signal voltage was to drop (computer lost power or died, cable unplugged or breaks).

Decision made not to upgrade to the higher sensitivity accelerometer because the vibration induced by the compressor is slightly higher than the 0.002 G noise we get from the current model.

Speaking of noise, I wrote an algorithm to simulate the noise and then wrote a deadband algorithm for the output.  The idea is to save wear and tear on the M2d and to prevent filtered, dried air from being wasted.

Mostly successful test.  The darn platform is just too heavy – I think if it weighed about 500 pounds it would work a lot smoother and more responsive.  The right roll actuator came loose at the bottom U-joint attachment point at the end.  Based on the graph it looks like if we upgraded to 3″ bore from 1.5″ cylinders and filter the noise from the accelerometer  we would be in business!

Couple of issues with the old laptop not being able to keep up with this interval… Kp probably set a little high… otherwise when it stopped at an angle, it stopped for good.

Amazing.  I should have gone to engineering school.  Apparently what I have been building with my tilt sensor and E/P transducer is a PID loop or proportional–integral–derivative controller.  And to make it worse there are numerous algorithms already defined using variables that have real names like “deadband” and “gain”.

I am working with Enfield Technologies, the experts in proportional control of pneumatics, and I think they have a product that would be more suited for our needs.

0.002 is the noise in G’s that we can expect to hear on the Phidgets board so if the last value is +- 0.002 then ignore it?

Hysteresis is 5%, is that our deadband?  5% of the total range?

Interval is 4ms (250 samples per second) limited by the Phidgets (the Enfield is 2.8ms)

Kp of 1
Ki of 0.02
Kd of 1

Nothing but trouble.  Installed the lateral spring assist assemblies and it appeared that the right roll transducer failed.  Next time I fired up the compressor the rear pitch transducer wasn’t working so I am guessing it is an icing problem because of the humidity.

Tests I ran ended up punching a small hole in the bottom sheathing because of a improperly placed support I made for transport.  Then I ended up breaking the wood bottom plate for the right roll actuator.  And there are noises from the left roll actuator’s linear bearing (probably damaged from side-load before I added the U-joints to the bottom of the roll actuators).

Overall very depressing!

I started looking at E/P Proportional 2/3 Valves last night but the cheapest I could find was $550.  I was looking for cheaper ones on eBay but found I found these 500-EH transducers on eBay for a fraction of the cost I paid for the replacement left roll transducer.  So I got to thinking that I can simulate a proportional valve programmatically by connecting the opposite transducer to the top port on the actuator.  Not sure if that will give me more control or not – I am also looking at flow control valves.

My dad and I got in a discussion about the grounding rod which is recommended in all cases by the generator manufacturer.  I told him that it just wasn’t feasible for a guy with a mobile attraction to drive a 4′ stake in the ground – a lot of times I will just be in the middle of a parking lot or tarmac!

250.34 Portable and Vehicle-Mounted Generators.
(A) Portable Generators. The frame of a portable generator shall not be required to be connected to a grounding electrode as defined in 250.52 for a system supplied by the generator under the following conditions:
(1) The generator supplies only equipment mounted on the generator, cord-and-plug-connected equipment through receptacles mounted on the generator, or both, and
(2) The non–current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator frame.
(B) Vehicle-Mounted Generators. The frame of a vehicle shall not be required to be connected to a grounding electrode as defined in 250.52 for a system supplied by a generator located on this vehicle under the following conditions:
(1) The frame of the generator is bonded to the vehicle frame, and
(2) The generator supplies only equipment located on the vehicle or cord-and-plug-connected equipment through receptacles mounted on the vehicle, or both equipment located on the vehicle and cord-and-plug-connected equipment through receptacles mounted on the vehicle or on the generator, and
(3) The non–current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator frame.

Ultimately, a guy on one of the forums that I like put it best.  It is a “floating ground” the same as the generator (alternator) battery and chassis ground in your car.  It is a closed system, every electron that leaves the alternator returns to the alternator… period.

On the ECS (Environmental Control System) front we made a decision to get a CR-2550 (latest generation smaller unit) because it has backup heat coils and the AUTO mode works better than on the CR-7000.

On the APU (Auxiliary Power Unit) front we ran some tests this weekend using an APC SC 1500 UPS.  These were done with and without the APC LE1200.  With the compressor running on our 550W air conditioning test unit we had very steady power from the DuroMax XP4400.  When the air conditioning compressor shuts off it takes an eternity for the SC 1500 to go back online with the LE1200 connected (very strange).

Ultimately it appears that with a minimum load of 500W aside from the UPS load and NOT using the LE1200 the generator works great.

I ordered an automatic switch from shore power to generator power when generator power is present.