What pressure do air-jacks run at??
Discussion
Hi all,
I've recently bought a TVR Tuscan Challenge car and it is fitted with air-jacks (4 of them). I've so far been unable to identify them but they look like AP ones. In case anyone can help, they're quite fat (around 4 inches diameter at a guess) with silver body and anodised red tops and locking nuts.
The connections that were in them (no pipes connecting them up) were 20bar push fit pipe connections. After going to my local Pirtek, the guy identified the connections and gave me some nylon pipe suited to the fittings so they're now all plumbed in. Before I start ordering any lance/bottle system to power them off though, does anyone know what sort of operating pressure I'm likely to need? The car is pretty light at around 900kg wet so I wouldn't have thought it would need tremendous pressure, but I have literally no idea at the moment other than < 20bar!
Any thoughts??
I've recently bought a TVR Tuscan Challenge car and it is fitted with air-jacks (4 of them). I've so far been unable to identify them but they look like AP ones. In case anyone can help, they're quite fat (around 4 inches diameter at a guess) with silver body and anodised red tops and locking nuts.
The connections that were in them (no pipes connecting them up) were 20bar push fit pipe connections. After going to my local Pirtek, the guy identified the connections and gave me some nylon pipe suited to the fittings so they're now all plumbed in. Before I start ordering any lance/bottle system to power them off though, does anyone know what sort of operating pressure I'm likely to need? The car is pretty light at around 900kg wet so I wouldn't have thought it would need tremendous pressure, but I have literally no idea at the moment other than < 20bar!
Any thoughts??
Assuming that the effective piston area is 50mm in diameter, it's area is 0.001963m^2. Four of them = 0.00785m^2.
That area has to support 900kg (call it 1500kg for safety).
Pressure=Force/Area = 1500/0.0078536 = 190995 kg/m^2 = 18.75 bar.
If you can find the effective piston area more accurately, and are perhaps willing to change the mass used in the equations, then you can reduce the pressure. But as close to 20 bar would be ideal.
That area has to support 900kg (call it 1500kg for safety).
Pressure=Force/Area = 1500/0.0078536 = 190995 kg/m^2 = 18.75 bar.
If you can find the effective piston area more accurately, and are perhaps willing to change the mass used in the equations, then you can reduce the pressure. But as close to 20 bar would be ideal.
If they have'nt been used for a while I'd very, very strongly recommend you rebuild them. It's not uncommon for them stick or not hold pressure when they get older!
Typical air jack pressure is "upto" 30Psi on newer models 25psi on others. Frankly I'd go to AP racing for the specs and also get a service kit cost whilst your at it.
Fundamentaly if the jacks and system are fresh, its just a case of applying air at an increasing rate, into the system to see whats required to lift it upto max pressure.
Typical air jack pressure is "upto" 30Psi on newer models 25psi on others. Frankly I'd go to AP racing for the specs and also get a service kit cost whilst your at it.
Fundamentaly if the jacks and system are fresh, its just a case of applying air at an increasing rate, into the system to see whats required to lift it upto max pressure.
Have you got any jack stands for them? If not you should get some.. then as soon as the car is in the air, you put the stands on around the legs, so even if air pressure goes the car stays in the air. I almost broke my ankle, when a pipe burst on an air jack.. We'd just got the car in the air, and I was stood next to the car when it went straight back down again..
Air jacks are great to use, but like everything they can be very dangerous if you dont take care..
Air jacks are great to use, but like everything they can be very dangerous if you dont take care..
No, not got any jack stands, though I do intend to get some for the reasons stated above, and so that I can safely stick my arms/head under the car when its up on them to do any quick tweeks under the car. Think I'll have to get some made down the local machine shop. Best get CADing!
Now here's the odd part, after speaking again with the previous owner (ran two of them in a team), the jacks are actually scratch built by the team. No wonder I couldn't find them on the net! Apparently they took some jacks they had, took them apart to see how they worked, and then built 8 of them specifically for the cars. I would never have guessed this as they have a very high quality of finish, are very well engineered and look to be in 'as new' off the shelf condition. And I would never have guessed that they weren't made by AP or another proper supplier. Anyway, the result of this is that there are no rebuild kits as they're unique.
He has kindly said though that he can send me pictures of the build and make me some more if any are faulty. Regarding operating pressure, he said 'whatever works, though we used to run them off an 8.5 bar compressor with no issues'.
I take it that its not very common to have diy airjacks??
He has kindly said though that he can send me pictures of the build and make me some more if any are faulty. Regarding operating pressure, he said 'whatever works, though we used to run them off an 8.5 bar compressor with no issues'.
I take it that its not very common to have diy airjacks??
I assume they are... I can't remember what Danny's ones look like though. I've got pics of his at home and I'll have a good look at mine now I know I'm not going to find any specs for them anywhere. Then I'll get in touch with Craig and see what pressure they run at if they're the same.
I'm amazed at how un-diy they look though. They have very nicely machined threaded bodies, red anodised aluminium bottoms, tops and locking nut things. Rubber 'feet' at the bottom of the jack cylinders and on the whole they feel very well put together. Very impressed. Maybe I'll get him to make me some more and start selling them over here
(he's based in Sweden)
I'm amazed at how un-diy they look though. They have very nicely machined threaded bodies, red anodised aluminium bottoms, tops and locking nut things. Rubber 'feet' at the bottom of the jack cylinders and on the whole they feel very well put together. Very impressed. Maybe I'll get him to make me some more and start selling them over here
(he's based in Sweden) Edited by 450Nick on Thursday 19th November 15:43
Hi Nick
You need to use an adjustable regulator and set it so it just lifts the car up,as the preasure drops in the bottle you can open the reg up to give you a few more lifts.
The jacks on Danny's car are AP and max preasure is 20 bar.
The bottle we use is a 300 bar bottle and you get plenty of lift's with it.
We have stripped the car completely body off full rebuild, as we have had some sponsership and they want Danny to give GT Cup a go next near (still going to do some rounds in the TVR Challenge depends on the dates not clashing.
If you want my mobile send me a pm ?
Cheers Craig
ps.. it was the drive flange that let go in the last race on the start line at oulton park.
You need to use an adjustable regulator and set it so it just lifts the car up,as the preasure drops in the bottle you can open the reg up to give you a few more lifts.
The jacks on Danny's car are AP and max preasure is 20 bar.
The bottle we use is a 300 bar bottle and you get plenty of lift's with it.
We have stripped the car completely body off full rebuild, as we have had some sponsership and they want Danny to give GT Cup a go next near (still going to do some rounds in the TVR Challenge depends on the dates not clashing.
If you want my mobile send me a pm ?
Cheers Craig
ps.. it was the drive flange that let go in the last race on the start line at oulton park.
If it looks like a carrot it must be the stub axle rather than the outer hub flange. That's the trouble with using something off a Ford Granada on something as powerful and torquey as a Tuscan I guess! I now carry two spares on the truck given the torque we run - and why we don't do standing starts!
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