Some of you have seen my on-board air solution using a Dive Cylinder and an adapted Scuba First Stage Regulator. Below is a how to and reference on where to get the parts from and how mine went together.
The CylinderYou can use a standard Steel Scuba Cylinder but they are heavy (especially when full) so i opted for a Carbon Fibre cylinder as it weighs next to nothing and easy to move about. Carbon Fibre cylinders are not typically used in Scuba diving due to the additional ballast you need to wear so they are more commonly used in Breathing apparatus. Don't bother going to your local Fire Station as they are not allowed to sell them, but there are places on the net. My personal choice is to use the Drager cylinders but brand new they are about £900 so below there is a places that sell secondhand ones.
http://www.stealthunter.co.uk/carbon-fibre-9ltr-cylinder-1267-p.aspGo for the 9 litre cylinder to maximize your air as filling a 35" tyre will certainly eat into your supply.
The lifespan of the cylinder can be up to 25 years, but if the cylinder has surface damage then it could be a throwaway item and the fill station will refuse
Cylinder TestingIf your cylinder is out of test then there is a company that i use called H-PAC (address below). It costs £30 which will last for 5 years and if you live too far away then shipping must be done with the cylinder empty. Interestingly enough the guy who owns H-PAC also owns Buildwas 4x4
H-Pac Services
Withy Rd Industrial Estate
Withy Road
Bilston
West Midlands
WV14 0RX
Tel: 01902 494988
Mounting the CylinderThere are loads of option to mount the cylinder, but i wanted a good quality mount so i used Power Tank in the USA. The link below shows the mount i used which will fit the 9 Litre cylinder. On my mount i had to shorten the strap to give a decent fit, but all it took was a drill, a few rivets and a hack saw. Below is the link for the Power Tank mount. and they also do rollcage mount clamps too.
http://www.powertank.com/products/productID/65
The Tricky bit (Scuba First Stage)Its not that hard to do (says an old Commercial Diver) but don't think you have to buy a new Scuba First Stage as it will never need to be tested ever again. BUT, you do need a specific type of First Stage. If you intend to use the Carbon Fibre cylinder (which are 300 Bar rated) then you need an appropriate First Stage to cope with the pressure.
The key word is "Din", not "Yoke" but "Din" fitting (see below)
This is what you need
A "Yoke" fitting will only work safely on a 232 Bar cylinder so you have been warned.Have a look on eBay for "Scuba Din First Stage Regulator" There will be loads and there is no need to buy new, for a half decent one expect to pay about £60-80, Poseidon, Oceanic, Scubapro, Apex are all excellent quality. You might want to get some spare "O" rings for the end of the Din fitting, if you lose one then all you'll get is a loud hiss when you open the bottle valve. These can be got from any dive centre or off eBay.
On all First Stages you will have HP (High Pressure) and LP (Low Pressure) ports.
The GaugeTo read the pressure you need to fit a gauge. You can buy them naked or with a hose already fitted, don't be scared to butcher the hose to gain access to the gauge fitting. On my set up i screwed it straight in to the HP port (High pressure Port) of the First Stage. Below is a link to give you an idea
http://www.simplyscuba.com/products/Suunto/SM36PressureGauge.aspxBut as with the First Stage, this doesn't need to be new, have a look on eBay for Scuba Gauge. All will go up to 300 Bar.
The HP and LP portsUnfortunately you can just screw in a 1/4 BSP fitting into the First Stage to we need a specific adapter. Good news is there is one available. The Gauge was easy as this will just screw straight into the HP port. The LP port has a thread size of 3/8 UNF and the company below does such an adapter.
http://www.bristolchanneldiving.co.uk/3_8_UNF_Male_X_1_4_BSP_Female_Adaptor-M9268This will allow you to fit Quick Coupler MALE 1/4" BSP
Please fit the Quick connect to the adapter before you screw it onto the first stage (its a fine thread)
If you want to put a 1/4 BSP fitting into the HP Port then you will need this adapter, but i do question what you want 300 Bar for? and chances are what you have at the other end wont last very long either!!
The bit you cant do (needs a dive Centre)The HP port is easy as this stays at what ever is in your cylinder. but the LP port needs to be reduced to 9 Bar (to run air tools) for example. On all First Stage's there is an adjuster (typically an 8mm Allen Key). Below you will see the "Main Spring". This is what needs adjusting with the help of a flow meter.
If you are unsure about the assembly of the above, then send me all the parts and i can get it set and tested on the Flow Meter. It will cost you a £10 plus postage back.
Where to get re-fills?Pretty much all dive centres offer cylinder fills. but below is a link that give a directory of locations where they do. The Dive centre will only fill "in test" cylinders and they normally take about an hour to do if the shop isn't busy (phone beforehand) especially on a Thursday or Friday as most people go diving at the weekend.
http://www.ukdiving.co.uk/business/category.php?cat_id=4The nice thing with the above set up is its mobile and if the site doesn't fancy a 300 bar cylinder near someones head then you can always take it out.
The word of warningA cylinder with any kind of pressure in it can on some occasions fracture and explode, please treat the cylinder with the utmost respect and never ever leave a cylinder in direct sunlight or a hot car for long periods. The best place to store one is in a cool garage during summer and inside a house during winter.
CostCylinder = £140
Power tank Mount = £110
First Stage = £60
Gauge = £30
Adapter = £15
Adjustment = £10
Approx total = £365
Any questions, just shout
