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Airbag spring monitoring/control

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Airbag spring monitoring/control

Unread postAuthor: daccel » Fri Aug 06, 2010 3:21 am

Been out of the loop for a while now, focusing on other interests (and getting firearms license this month so there probably won't be any more small hybrids from me :P), but I'm designing something that I could use your guys' input on since the components are related to spudding.

Project in question:
Image

Image

They're airbag helper springs that sit between the rear leaf springs and the frame, to keep the truck level and not wreck the soft stock leafs when hauling a lot of weight.

I want to be able to monitor and control the pressure in them (5-50psi) and the tank (100-200+psi) from the cab. I could buy a control system, but it would be $300+, which I don't feel like spending on something I should be able to make for a lot less.

This is the basic idea, not to scale:
Image

Basically looking at 2 options each for monitoring/control. Either run hose up to the panel with regular gauges, or pull apart digital tire gauges and extend sensor or lcd. Either use 4 solenoid valves or run hose to panel and machine a set of spool valves into aluminum to have push button control.

And the panel has to be compact, clean and attractive - a bundle of plumbing parts isn't an option here, not that there's anything wrong with that :lol:.

I will work on some more drawings and finish pricing out options, but any initial thoughts? I promise eventual video of more exciting uses than airbags for on-board air, potentially from fridge compressor in custom tanks! 8)
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Unread postAuthor: POLAND_SPUD » Fri Aug 06, 2010 3:45 am

do you want to be able to control the pressure in each airbag ? If not then you need just one regulator (preferably one that is accessible form the inside of the car)
Quite a lot of valves and regs can be panel mounted... just get a small steel plate and drill nice hole in them for the reg and the valve/valves

One of these toggle valves would probably be the best for your needs
http://www.clippard.com/store/display_d ... sku=FTV-3P

also it would be pretty cool if you could get a AC car compressor... mounting that thing might be a bit tricky but that would simplyfy a lot (no need to mount an inverter + you can use it as an all purpose on board air compressor)

also these things have an electromagnetic clutch so it's not that they put load on your motor all the time.... you can add an on/off switch on your control panel and a pressure sensor that will automatically turn it off when the tank reaches 200 psi or so
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Unread postAuthor: daccel » Fri Aug 06, 2010 9:10 am

Yes they need to be individually controlled, or at least isolated from each other so that air doesn't transfer between with an uneven load or when cornering.

I wasn't going to have a regulator, just two valves for each bag, air in and air out. But I guess I could have a central regulator, two check valves, and then individual exhaust valves. Or maybe one exhaust valve and another set of check valves would also work. The regulator would probably be a good safety anyways so that the max pressure of bags isn't accidentally exceeded (100psi).

I actually have a 1000w inverter which I want to install anyways, so I think a regular fridge compressor would be easier in this case - just buy a pressure switch and plug it in.

Hey I almost have all the parts of your standard answer, that's why the quick reply :wink:.
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Unread postAuthor: POLAND_SPUD » Fri Aug 06, 2010 12:47 pm

that's why the quick reply

Yeah :D

Ohh then a 3 position valve would be the best... in one position it fills the airbag, in the second vents it and blocks the flow in neutral position

Otherwise you'd need 4 two way valves (two for filling and two for venting). However as 3 position valves are a bit pricey it it's not such a bad idea

EDIT
Though, on the second thought two 3 way valves might be enough. The only problem is that the circuit would require two regulators (non-relieving). The added advantage is you can regulate pressure in each airbag individually, which might be useful if there is more mass one one side of the car.
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Unread postAuthor: daccel » Tue Aug 10, 2010 12:21 am

It just so happened the 5 way 3 position valves were on sale for $30, only 5 more than the regular solenoid valve also in the picture, so I picked up two:

Image

I will plug 2 ports, B and Be, so that it functions as a 3 way 3 position valve - fill/off/exhaust. So pretty much how you said, but shouldn't need regulators, just fill/exhaust until desired pressure is reached.

I wanted to have the cab side all electric, but looking at those digital tire gauges, they seem to automatically turn off, and automatically tare when turned on, which wouldn't work in a constantly pressurized system. Any suggestions on this front would be helpful... should I write off this option?
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Unread postAuthor: Technician1002 » Tue Aug 10, 2010 12:46 am

daccel wrote:
I actually have a 1000w inverter which I want to install anyways, so I think a regular fridge compressor would be easier in this case - just buy a pressure switch and plug it in.

Hey I almost have all the parts of your standard answer, that's why the quick reply :wink:.


Since you need a 100 PSI limit, and have a 1KW inverter, consider using a Harbor Freight 3 gallon 1/3 hp compressor. Factory set for 100 PSI, comes with a regulator and safety pop off valve. They do run fine on a 1KW inverter. This setup would include all the parts you would have to add on to a fridge compressor such as pressure switch, accumulator, regulator, and relief valve.

My inverter in the trunk;
Image

The compressor;
Image

Running filling my large cannon in the field;
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Unread postAuthor: POLAND_SPUD » Tue Aug 10, 2010 2:22 am

I will plug 2 ports, B and Be
pluging the exhaust isn't the best idea. Basically speaking they might get stuck in one position. Though they might work just fine, so just test them.



ohh BTW nice find :D
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Unread postAuthor: daccel » Tue Aug 10, 2010 9:06 am

You may have mentioned this at some point in the past, but what gauge wire do you use for the inverter, and how long a run is it to the trunk? I want to keep it as short as possible since heavier gauge is more expensive, so will probably have it under the drivers seat.

Yes, I came to the same conclusion myself when I started adding up all the parts plus the fridge compressor to make it work. Got the small dewalt trim compressor. Plus that way it's a bit more versatile, can use it for work too.

I did test plugging the second pressure port, but good point, I should test exhaust. Although I guess it doesn't matter leaving it open, will just lose a very small volume of air behind the plug when the valve cycles.

Yeah, I was rather pleased with the find :). Canadian spudders, I recommend checking out Princess Auto!
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Unread postAuthor: Technician1002 » Tue Aug 10, 2010 11:42 am

My car is a prius, so the battery is already in the trunk. The power cable is a 2AWG welding cable 3 feet long. I did not want a 12 volt power brownout and inverter shutdown when starting the compressor at the cut in pressure. The inverter came with a 3 foot 6AWG cable. I went larger for surge capacity or a later upgrade to a 2 KW inverter. The book that comes with the inverter gives minimum wire size for different lengths. My book covered both the 1KW and 2KW models. I wired for the 2KW + a size larger for starting compressors. My charging system on the car can not handle a 2KW steady load.
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Unread postAuthor: daccel » Mon Aug 16, 2010 1:30 am

It works :D. Nice when things work as planned.

Or at least mostly work... the pressure on the passenger bag creeps up, which is strange, I was expecting leaks not a pressure increase. Got home from where I was installing tonight and it was up to 50 psi on that side! All I can think is that some dirt got in the valve and it isn't closing fully. Although the compressor had fallen over and pulled the tube on the valves pretty hard, so maybe that did something, but it was too dark to trouble shoot.

This is the temporary setup, will make something out of aluminum to mount and protect it once all the kinks are ironed out:

Image

This is why it took all afternoon and evening to install, fishing all that through existing holes in the truck by myself, and the inverter wire is aluminum so it's very stiff, good times:

Image

Where the panel will be mounted:

Image

Gauges:

Image

The inverter wire is 2/0, it will be a 12' run after I trim it down, so I went bigger:

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Unread postAuthor: POLAND_SPUD » Mon Aug 16, 2010 4:55 am

Nice good to know that it work as planned... how much did you spend on it ?

ohh I see that you've used push to connect fittings and tubing...
Get that stuff if you can... it is really really convenient... if you try it once you'd never get back to hose barbs, clamps etc.
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Last edited by POLAND_SPUD on Mon Aug 16, 2010 10:31 am, edited 1 time in total.
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Unread postAuthor: Technician1002 » Mon Aug 16, 2010 9:58 am

Aluminum wire is a fire hazard in a high vibration environment. Please change it to copper. There is a reason aluminum wire is not used in vehicles and house wiring.

Most places only permit aluminum wire for the service entrance inside conduit, not from the panel to the outlets outside of conduit. There is a reason for that. Many house fires started from aluminum house wire in the 1960's. It was banned shortly after.

If you do use aluminum, use connectors approved for use and use a torque wrench and no-ox on all connections. The stuff is very unforgiving.

I very highly recommend wire made for rough service high flex use such as welding cable for arc welding. You can pick up the cable and the lugs to go on the ends at any well stocked welding supply shop.

Don't waste money on the show off stuff from a high end performance car stereo shop. That stuff is either cheaply made or has high mark up. You do not need high definition clear power wire. Welding cable has much better insulation and will hold up to 4X4 off road adventure that slices up the pretty stuff.
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Unread postAuthor: daccel » Thu Aug 26, 2010 1:05 am

Seems the leak problem was caused by trying to operate the valve below the minimum pressure so it didn't close completely.

For all components and inverter and compressor it will be $600 +/- 100. A bit steep, but with the on board power and air now, it is quite a versatile setup beyond just the adjustable suspension.

Thanks for the heads up on aluminum wire. I did a bit of research and it sounds like it's not the wire that's the problem but the connection between aluminum and copper due to reaction between metals, oxidation and different expansion rates with heat. Is that your understanding?
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Unread postAuthor: Technician1002 » Thu Aug 26, 2010 10:03 am

Aluminum wire has two issues. The first is the item you mentioned. The second is the limited number of bends you get before it work hardens and cracks. This causes a high resistance point on the wire and localized heating. Unlike a home where it is installed and never moves, vibration in a truck will fatigue the wire and cause this failure.

Aluminum wire is unsuitable for mobile use due to this second reason.
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