Hi Sam,

"Just back from three months in Sahara, grand Erg was just the job many times. In reality, takes a minimum of five minutes to get each tyre back to road pressure (37psi), and sometimes nearer ten. .... Sam"

Thats is worse than the performance of my little Thomas unit (asuming 7.50R16 tyres).

What, according to Grand Erg, is the problem and what do they propose to improove in detail?

GE provides a table with inflation times on their web site: http://www.granderg.com/compressori.htm

So if the compressor does not fit thees promisses, then it should not be your turn to pay the repair!!??

I will observe this thread, it might get interesting for my german site www.sahara-info.ch

Good luck, Yves

__________________
Yves

Okay,

Took the motor out and sent it off to Grand Erg. It was a 24V motor, no wonder it wasn't very impressive! A replacement motor has just arrived, I will fit it this weekend and see how it goes.

Off to Algeria in three weeks, where the wee beastie will get lots of use and will report back afterwards - expecting to be suitably impressed - we shall see.

Sam.

Adding another option to the menu:

I am currently installing a 12V ExtremeAire compressor, to my Defender 6x6 conversion, after originally planning to use an inverter and a 240V compressor. (I found my 1500Watt inverter tripped out because the AC induction motor pulls a LOT more current on start-up than its nominal power requirement).

The Extremeaire has 100% duty cycle, which is useful (6 tyres can take quite a while to inflate!). They claim a 4 cfm free flow rate, which is supposed to inflate a 33x12.5x15 tyre from 15psi to 30psi in 90 seconds!)

Cost is a bit frightening at £240, plus freight, plus VAT, though.

I will report back when I've used it in anger

Regards,

Michael

__________________
Michael & Sandy
http://www.expeditionoverland.com

Noooooo, NEVER take a 12V feed directly off a 24V system. Lots of ill-informed debate on this issue, but the short answer is that even a trickle feed off of one battery will sooner or later (and usually sooner) ruin one or both batteries.

Yes, you'll get nice clean 12V from the battery, (which is all Daerr care about, apparently) but the 24V charging system will do some nasty things as it tries to replace the charge.

Remember, the batteries are being charged in series. Imagine one is empty, and the other full. This is NOT the same as charging two batteries in parallel - the empty one will never get full, and the full one will be overcharged. They will both die, one slowly and painfully, and other possibly messily and spectacularly.

The website suggested you do this either knows nothing about batteries, or they own shares in a battery manufacturer!

Regards,

Michael...
P.S. You can get some electronic 24V to 12V converters, but it'd be hell of expensive and bulky to cope with, say, 30 or 40 amps (which I would guess might be what these compressors would draw).

__________________
Michael & Sandy
http://www.expeditionoverland.com

Gotta keep a good thread going.
I'm looking forward to Michael's info on the ExtremeAire, which seems to be, along with the exorbitant Grand Erg, the only electric comp which comes near my needs. I've also looked at 240 volt compressors (got a 2.5kw genny) but when I told the super specialist salesman that it has to take 6 tyres to 75psi he took me to a bloody great belt driven monster that I just can't pack anywhere.
As with the hyd/elec winch argument, the electric compressor is much simpler than running off the engine, but the engine has a few more watts. I've finally figured out where I can move the alt to in order to accomodate an a/c comp (not much space under an Iveco bonnet), now I'm looking for a suitable unit. Stacks of web info on choosing a US one, but not much for europe. Does anyone know of a european vehicle which uses a York comp? Or how to spot a decent self lubricating one of the barrel shape?

Michael, if you're running tyres that will take it (XZL or XZY do) could you do me a favour and time your comp up to 75psi to give me a better idea of whether the electric is worth the hassle saved in not messing around with fan belts. Congrats on taking the plunge, do they offer an anti meltdown guarantee? If they claim 100% duty cycle they should.
Thx for all
Luke

Luke,

Speak to Bob at Motor Climate

66-102 Cherrywood Road, Bordesley Green
Birmingham B9 4UD, United Kingdom
Tel: +44 (121) 766 5006, Fax: +44 (121) 772 8397

They can supply York mini and super compact compressors with double groove clutch units.

True about the engine power being used more wisely to run a compressor rather than running a generator to convert engine power into electric power to be further coverted into electric motor power moving the compressor's piston. It's like using an voltage converter to step up 12V to 240V to run a device charging a 6V battery. Silly, isn't it?

The CO tank has been already discussed here and the idea discarded as not practical in long range travel conditions. 40 tyres is just ten instances of reinflation, which may be OK for weekend off-roading but certainly not a lot on a longer trip.

------------------
Roman (UK)
www.polandrover.com

__________________
----------------
Roman (UK)

I was recently sent some details of an american compressor designed for engine mounting - will dig out the details

As for running a workshop compressor type arrangement - thats exactly what I do.

I have a small 100 Litre Per minute compressor (B&Q sell them for running nailguns) and run it off a 1500 watt inverter

Pumps up my tyres no problem (10.5/20 Unimog tyres on a LR101)



------------------
Rich
LR101 300Tdi Ambi 'Tiggurr'

__________________
Rich

Iveco Turbo Daily 4x4 40-10
Ex Owner LR101 300Tdi Ambi 'Tiggurr'

I wouldn’t say we dismissed the CO2 tank idea (although I have an engine mounted York). I calculated that number (40 tires) when inflating a bigger than average 31”x10.5 tire from only 10 PSI to 30 PSI. In a real expedition you will only re-inflate to that pressure when you hit the tarmac again. For your other 10 times you will only re-inflate to say 20 PSI after getting unstuck. And will you really need to re-inflate 10 times? I’ve been on some long trips and I never had to inflate more than 4 times. And that includes the great sand sea.

It’s a great option for those who don’t want, or don’t know how, to modify their engine bays to accommodate an engine driven compressor and want something faster and more reliable than an electric one.

Take a look at the charts on this page: http://www.powertank.com/chart.htm

A Sanden compressor will work too and has a much smaller profile, however it will need to be oiled often as it doesn’t hold oil as good as Yorks.

------------------
A.B.

OasisPhoto.com – Images from the Magical Sahara.
ShortWheelbase.com – Jeep preparations.

__________________
A.B.
OasisPhoto.com – Images from the Magical Sahara.

Hi Luke et al...

Got back from Morocco a few days ago - had a fabulous trip!

I've never had much success with 12V compressors before - they never seem to come anywhere close to the manufacturers' claims in real life operation. And most often even the manufacturers' claims amount to barely acceptable performance if you're pumping lots of big tyres.

Unfortunately, the Extremeaire didn't live up to my expectations. It should have been adding one bar to each of my tyres in around 1 minute, without any holding tanks. (Extremeaire quote a free flow of 4CFM, wich equates to someting over 100 litres perminute, unless my arithmetic is faulty).

To confuse the issue though, I have installed 2 x 20 litre holding tanks, which pressurise to 10Bar before turning off the pump.

However, even with these tanks fully charged to 10Bar BEFORE I started filling the tyres, pumping all 6 of my tyres from 1.5 to 2.5Bar took 25 minutes!

I calculate that each of my tyres as a volume of 100 litres, so upping the pressure by 100kPa should need a total of 600 litres of air for the set. The 40 litres of holding tank should provide around half the air needed. (I guess the pressure can fall from 10Bar to around 3Bar and still pump a tyre to 2.5. So there is 7Bar worth of usable pressure, times 40 litres, equals nearly 300 litres.)

So I would have expected 3 minutes to pump all my tyres, not 15! Incidentally, filling the 40 litre holding tanks from zero to 10Bar takes more than 20 minutes too, which is disappointing, amounting to an average flow rate of only 20 litres per minute. It doesn't slow down significantly towards the end.

At this stage I am hoping that the fault lies in an air system blockage (maybe a faulty non-return valve?). Or maybe my electrics are not providing enough current. Or maybe my pump is faulty. Or the whole 12V thing is just unworkable.

On the plus side, on one occasion we did run the pump for over an hour, continuously, pumping tyre on several vehicles, in a 38 deg C ambient temp, and the pump got hot, but not unduly so...

I'll keep you informed once I get to the bottom of the issue, if anyone is interested.

Meanwhile, I am thinking engine-driven mechanical pumps...

Regards,

Michael


[This message has been edited by SandyM (edited 26 November 2002).]

__________________
Michael & Sandy
http://www.expeditionoverland.com

Okay,

Tried out the grand erg, with the 12v motor - wow!!

Didn't bother with stats, from v.flat to road-ready-to-go max 90 secs per 7.50R16. Ace with motorbike tyres as well!

Expensive, but a good LONG TERM investment.

Sam.

PS just make sure you get a 12v, not 24v, unit for your 4wd!

An update on my ExtremeAire compressor. Good news - I discovered it was the one-way valve that was constricting the air flow. The very first fitting I screwed into the pump!

I took this out, and attached an air-line directly to the pump. It fills my 110 litre tyre (255/85-16) from absolutely flat to 1 Bar in 90 secs. Another two and a half minutes to raise the pressure from 2.5 Bar, making a total of 4 minutes. I would expect this to take just under 3 minutes according to spec, but I can live with 4 mins.

It also now takes under 10 minutes to fill my 50 litres of holding tank to 10 Bar. (Incidentally, astute Gentle Readers will notice I am not 100% certain of their capacity - I thought they were 20 litres each, but now I believe they are 25 litres each).

I am much happier now!

Regards,

Michael

__________________
Michael & Sandy
http://www.expeditionoverland.com

All you ever wanted to know about this subject!

Sam.

many thanks to all and expecially to A.B. for his tech advise. I bought an old ('81) Range Rover 3.5 V8 and I noticed that the original A/C compressor was a long-stroke York, so I decided to make the mods well described by A.B.
After a trip in the Lybian desert I can confirm all the performances described in the post; it pump up tyres in seconds and can reseat punctured tyres (luckily not mine!).
The only problem is that the compressor sprays oil from the outlet port to the tank, filling also the thin plastic tube of the pressure relief with the need of frequent services. The compressor was filled with the recommended amount of mineral oil (see the RR Workshop Manual or the York compressors manual at www.onboardair.com) On this manuals is recommended to check the oil level after some working time, so it seems that a little oil is intended to mix to the cooling fluid maybe via some passage in the cylinder head.In an open circuit pumping air like mine this would result in a continuos leakage. Can someone give further informations before I start opening the compressor's head?
Thanks
Gipo

You’re welcome Gipo, glad to have helped.

First off, oil is not good for the tires and will shorten its life. If the tires are new or in good condition, I would dismount them and clean both the tires and rims well with detergent to remove the thin oil film that formed on them. If the tires are a bit old or will be replaced soon then don’t bother.

Continuous leakage, as you call it, is normal since as you said this is an open circuit with no recycling of fluids or even air. What we do is install an air filter on the outlet of the compressor to catch all the oil. Make sure it’s a good quality filter that 1) filters well and 2) can handle the pressure of the pump.

Most filters have a drain plug at the bottom of the collected oil cone reservoir to drain the oil. You can connect that drain hole to the air inlet of the compressor and install some sort of faucet or valve. Every few hours of use open the valve and the compressor will suck the oil back in.

From my personal experience I’ve never been able to fill the compressor to the level recommended by the manufacturer. It spits almost all the oil back out. And the oil filter <-> air intake trick I mentioned above didn’t work for me since my compressor “leakage”, which I got used, was excessive. Every few months, in order to keep my compressor lubricated, I disconnect the outlet hose and attach a small 20cm hose that ends in a small container. I turn the compressor on and slowly pour oil in the filler/dipstick plug. I keep doing that for a few minutes to make sure that all the components get lubricated. I stop pouring the oil but keep the compressor running for a couple of minutes to catch the excess (if I can call it that) oil then hook everything back together. When I first installed the compressor and found that this is all I can do, I didn’t think it would survive long as the oil seems to be insufficient. I set aside money for a new compressor unit but 5 years down the road, I still use that same old compressor with great results even though I make it work pretty hard. Usually when I’m on a trip the electric compressors are never taken out of their cased my compressor does all the work.

------------------
A.B.

OasisPhoto.com – Images from the Magical Sahara.
ShortWheelbase.com – Jeep preparations.

__________________
A.B.
OasisPhoto.com – Images from the Magical Sahara.

After rather bad experiences with different electric compressors (Truckair, ARB, Grand Erg and others) we decided to buy an EMS compressor M55. It is extremly heatresistant (we use it mainly on Sahara trips), very fast and the price is almost the same as for GRAND ERG. Even refilling the tires of three cars in a row on hot days was never a problem. Only disadvantage: EMS compressors are rather big. So we decided to keep it in a plastic container instead of fixing it permanently in the car. Here in Germany EMS is sold by BEDUIN tents & more.
http://www.dachzelte-und-mehr.de/KOM...pressoren.html
Regards
Joe