Dave W Posted October 1, 2008 Share Posted October 1, 2008 After killing my old ARB compressor I bought a new high output ARB compressor via Britpart. Although the air volume seems much better than the old style one it has a much smaller reservoir tank which got me thinking... I have a large protected "hole" under the floor behind the seats where the 8274 for the rear was mounted originally - I've now moved it into the rear cross member. The "hole" is large enough to mount one of these in: http://www.mattsavage.com/acatalog/info_91020.html This tank takes the same fittings as the ARB (1/4 NPT) so I could move the pressure switch onto it and link directly to it. OTOH I currently have a quick release connector on the compressor that has a short airline extension on it that provides a point for plugging in an airline at the side of the navigators seat. I'm considering keeping the quick release on the compressor and running a line from that to the new tank, leaving the pressure switch on the compressor as it's out of the elements there. That way if I have a problem with the tank or it's fittings I can quickly unplug it and be able to use the lockers still. I'll then run an airline with a quick release connector to each side of the vehicle for the tyre inflator, each from it's own port on the tank. Anything I need to think about/beware of ? I'm assuming one of the 5 ports is at the bottom of the tank so I'll need to rig up a drain valve there... Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted October 1, 2008 Share Posted October 1, 2008 How much is that tank? Bet its a lot more expensive than a truck air reservoir from the scrappy. Quote Link to comment Share on other sites More sharing options...
Dave W Posted October 1, 2008 Author Share Posted October 1, 2008 It's 54 quid including VAT... so yep, a lot more expensive but OTOH I've not seen a truck one that small. By the time I've added all the fittings and extra airline I reckon it'll cost me about 100 quid for the lot... so less than one trip to the petrol station Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted October 1, 2008 Share Posted October 1, 2008 I bought a 25L workshop compressor tank for 20 quid delivered. It's going to be heavier, but then otoh should stand up to any abuse for longer. Quote Link to comment Share on other sites More sharing options...
Dave W Posted October 1, 2008 Author Share Posted October 1, 2008 I bought a 25L workshop compressor tank for 20 quid delivered. It's going to be heavier, but then otoh should stand up to any abuse for longer. I appreciate the suggestion but I really don't think that'll fit under my motor and I don't think a 2cfm compressor would get it up to pressure in a reasonable time I know I'm a Yorkshireman but I'm really not that fussed If I can buy something that is tested, will fit straight in and will do the job I don't see that as an unreasonable price. Although I did think about converting a couple of those little disposable CO2 bottles that you can get for MiG welders, I used to have a few kicking about in my shed but think they may have gone to the scrappers. Soooo..... other than getting a tank cheaper, would the setup work OK ? Quote Link to comment Share on other sites More sharing options...
SteveG Posted October 1, 2008 Share Posted October 1, 2008 Anything I need to think about/beware of ? I'm assuming one of the 5 ports is at the bottom of the tank so I'll need to rig up a drain valve there... It's good practice to fit a pressure release valve to a tank that operates at or less than it's maximum pressure. So if you have a pressure release valve, drain tap and compressor input you'll have only two outlets left. So may be worth buying the 6 port version for all of £2.15 more I have the 2.5G tank and it's a nice compact tank. I would also advise giving it a spray with waxoyl/dinitrol when fitted as mine soon started rusting. Cheers Steve Quote Link to comment Share on other sites More sharing options...
SteveG Posted October 1, 2008 Share Posted October 1, 2008 Soooo..... other than getting a tank cheaper, would the setup work OK ? Yes, my only concern that if you are running the tank off the same pressurised feed as your locker solenoids is that if you lose pressure on the tank from something like a hose ripped off etc, you lose the operation of your lockers, so it's probably worthwhile fitting an isolating valve inline to the tank feed, or easliy being able to pull off the quick release line would do the same thing. Cheers Steve Quote Link to comment Share on other sites More sharing options...
Dave W Posted October 1, 2008 Author Share Posted October 1, 2008 Now you come to mention it, 5 ports doesn't seem that many, probably not a good idea to use them all up straight away I thought by keeping the current quick release I can isolate the current working ARB setup from the new tank "just in case". The compressor is just behind the navigators seat so easily accessible if needs be. I'll be able to unplug the tank and plug the tyre inflator line in too if all else fails. MattSavage also do a tank port fitting kit which includes a relief valve, drain valve, pipe connector and a couple of port blanks so I guess one of those will sort out most of the fittings I'll need, will have to see if they do the bits individually. Quote Link to comment Share on other sites More sharing options...
dollythelw Posted October 1, 2008 Share Posted October 1, 2008 disposible party balloon tank = £free from any kids party place, has a blow off disc, drill it to BSP and jobs done, weighs bugger all manifolds are easy - lenght of nominal bore tube, drilled and tapped with as many outlets as you like Quote Link to comment Share on other sites More sharing options...
TSD Posted October 1, 2008 Share Posted October 1, 2008 It's good practice to fit a pressure release valve to a tank that operates at or less than it's maximum pressure. It's good practice to run away from one operating above it Quote Link to comment Share on other sites More sharing options...
Dave W Posted October 1, 2008 Author Share Posted October 1, 2008 It's good practice to run away from one operating above it Lol Quote Link to comment Share on other sites More sharing options...
robhybrid Posted October 1, 2008 Share Posted October 1, 2008 I am not entirely sure it is a good idea to run a arb compressor with an auxilary tank Your pump will have to work at a higher pressure for longer as it fills up your tank, not good I believe there is a good reason why the newer ARB compressors have a smaller tank. I think it is a good thing to reduce pump running time not increase it. Think long and hard about why you need that air reservouir. For back up air to power your lockers in event of compressor failure has anybody tried plugging their air pump up kit onto the spare tyre? although the pressure switch setting is much higher how much pressure is needed to activate a locker? Quote Link to comment Share on other sites More sharing options...
Dave W Posted October 2, 2008 Author Share Posted October 2, 2008 The primary reasons for fitting a tank are: 1) It means that the motor doesn't have to run every time I switch a locker in - the old compressor would switch a locker in 2 or 3 times without running, the new one won't do 1 without running. With an air tank, with no leaks, I'll probably be able to operate the lockers a lot of times before the pump is needed, maybe even get a few hours of use without the pump running. 2) Quicker tyre inflation - the reservoir of air allows the pump to work more efficiently as you move around the vehicle inflating tyres and gives you a "head start" when you first start inflating the tyres. The gaps in inflation where you are checking the pressure or moving to the next tyre are no longer wasted time as the pump is storing air while you're not inflating. I will need to add a trigger to the current ARB airline or, more likely, replace it with a gauge and trigger to make use of the tank. I'm not sure what quantity of air is required to take a 35x10.5 16 Simex from, say, 10psi to 24psi and how that equates to the quantity of air stored in a 2 or 2.5 gallon tank at 100psi. Gut feeling suggests to me there may even be enough reserve to inflate one tyre from the tank... but i wouldn't know where to start with calculating that ! I assume you'd want to calculate the volumes of air required at atmospheric pressure in each case.... anyone ? In, probably way too simple terms, I'd expect 2.5 gallons of air at 100 psi to take up 10 gallons volume at 25psi but I'm sure there will be some kind of none linear formula for it that'll make it far more complex in reality ! Quote Link to comment Share on other sites More sharing options...
Dave W Posted October 2, 2008 Author Share Posted October 2, 2008 Here are some calculations based on Boyles law and assuming an atmospheric pressure of 14 psi and based on a Simex containing 3.5 cubic feet of air (very roughly 35x10.5 16 tyre).... To take a Simex from 0 to 10 psi (which is actually from 14 to 24psi thanks to atmospheric pressure) will take 6 cubic feet of air. To take a Simex from 0 to 25 psi (14 to 39) will take 9.75 cubic feet of air so we need 3.75 cu ft to inflate a tyre from 10psi to 25psi which will take a 2 cfm compressor such as the ARB just short of 2 minutes. A 2.5 gallon tank is 0.4 cubic feet and will hold 3.25 cu ft of air at 100 psi and 1.11 cu ft at 25 psi giving us 2.14 cu ft usable air above 25psi. So... when inflating from 10 to 25 psi we need 3.75 cu ft of air and the tank has just over half of that available at the start, the compressor on it's own will take just short of 2 minutes to air up the tyre, with the tank the first tyre will take under a minute to inflate, subsequent tyres will gain up to a minute, depending on how long it takes to move from tyre to tyre as the tank recharges. You also gain back some time each time you stop inflating to check the current pressure. It will take over a minute for the compressor to get the tank back to full charge from 25 psi but I'd have thought at least 30 seconds of that would be accounted for by the time it takes to check the pressure during inflation, screw/unscrew valve caps, move the airline about and, in my case, fit the valve stem adaptor.. I'd guestimate you're looking at 7 minutes with a tank and 10 minutes without a tank to air up all 4 tyres, to save time kneeling in the mud, let the tank finish filling up before each tyre that way, with the tank, you spend 4 minutes kneeling in the mud instead of 8 without the tank Quote Link to comment Share on other sites More sharing options...
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