Compressor & Impact Wrench questions

[Roger928]

Second question, the compressor pressurises to 8 bar, but doesn't restart until the pressure in the receiver is down to something between 5 and 6 bar. Does anyone know if there's any way of adjusting this?

The factory settings for your air compressor pressure switch are the correct settings. Your compressor is designed to run properly at those cut in and cut out settings. In attempting to establish pressure settings higher than those from the factory, a compressor may become unsafe, and it surely will self-destruct a lot sooner than expected.

 

[lostinthelight]

If the f/r button is faulty/sticking then air could be split between both directions which could result in the syptoms you describe.?
litl

 

[aesmith]

The factory settings for your air compressor pressure switch are the correct settings. Your compressor is designed to run properly at those cut in and cut out settings. In attempting to establish pressure settings higher than those from the factory, a compressor may become unsafe, and it surely will self-destruct a lot sooner than expected.

Would changing the cut-in pressure alone have that effect, so long as the upper cut-out pressure remains unchanged? I accept that the motor would run more often, but not more in total. In fact maybe less because at the moment if I've used a bit of air but need a decent pressure, the only way is to vent off more until finally the pump cuts back in and recharges.

 

[aesmith]

If the f/r button is faulty/sticking then air could be split between both directions which could result in the syptoms you describe.?
litl

Cheers, that's something to check once I have it in bits, make sure the button is going through it's full travel.

 

[SammyInnit]

Would changing the cut-in pressure alone have that effect, so long as the upper cut-out pressure remains unchanged? I accept that the motor would run more often, but not more in total. In fact maybe less because at the moment if I've used a bit of air but need a decent pressure, the only way is to vent off more until finally the pump cuts back in and recharges.

Duty cycle isn't equal to just running time. Easiest way of considering duty cycle is to look at welders.

The higher the current draw the lower the duty cycle. Same principle applies. While what you say on paper is correct, the fact it will work harder more often to hit the peak will lower it's duty cycle.

This is to say you need the base line of working pressure to be any higher, you don't. You need a better wrench.

 

[aesmith]

I think I may have ruled out the air supply as the issue. Firstly because it works every single time in forwards, and when it runs out of torque fully tightening the bolt it still hammers trying to tighten it further. It's definitely more powerful and lively at say 90psi compared to 55 or so just before the pump cuts back in, but in forwards it still tries even at the lowest pressure. Secondly even with an awful lot of fiddling and testing it wasn't causing the pump to kick in any more than say once in 15 minutes, so for most of the time it wouldn't make the slightest difference having a more powerful pump. Finally the function was exactly the same with 10m of thin 5mm bore curly pipe. I can't readily measure whether there was a reduction in max torque, but the appearance was the same - works every time in forwards and continues to hammer after fully tightening, in reverse it doesn't hammer at all on something like four out of five attempts.

I have the wrench in bits now, nothing is obviously wrong so I need to understand the rocking dog hammer mechanism. It seems to me that in reverse when it hits resistance it sticks, instead of rocking.

 

[Tigercubrider]

I know that tinkering with stuff is the purpose of a diy site but they are bloody cheap
Maybe just buy a new one?

 

[Burnerman]

A rocking dog mechanism has certain similarities to that of an inertia seatbelt......spin the belt reel by hand and centrifugal force causes the mechanism to lock.
For the rocking dog to work and lock the rotor to the anvil, the rotor has to spin bloody fast, and it will only do that if the vanes are free to slide in the slots on the rotor.
5mm air supply pipe is nowhere enough - 10mm is the minimum, and keep it a short length of hose if you can. That hose has to supply quite a large CFM!
Your wrench will always work better tightening as it slowly rotates the nut a bit at a time.....many a cheap wrench will give up if a nut is very tight. The rocking mechanism should still work, of course and you'll hear that.
John

 

[aesmith]

A rocking dog mechanism has certain similarities to that of an inertia seatbelt......spin the belt reel by hand and centrifugal force causes the mechanism to lock.
For the rocking dog to work and lock the rotor to the anvil, the rotor has to spin bloody fast, and it will only do that if the vanes are free to slide in the slots on the rotor.
5mm air supply pipe is nowhere enough - 10mm is the minimum, and keep it a short length of hose if you can. That hose has to supply quite a large CFM!
Your wrench will always work better tightening as it slowly rotates the nut a bit at a time.....many a cheap wrench will give up if a nut is very tight. The rocking mechanism should still work, of course and you'll hear that.
John

That comes back to the point I've been trying to make, when it sulks in reverse nothing turns at all. It's not that it's too slow for the dog to lock and hammer, the dog locks and stops it rotating at all. Only in reverse. I still really can't see how that could be caused by poor airflow - at that point it's not using any air at all.

 

[DaveHerns]

Get a new wrench. I took mine apart and never got it working properly.

 

[Burnerman]

Fair comment from Dave......I'd like to try the wrench on someone else's air supply which was known to be powerful enough.
John

 

[SammyInnit]

Fair comment from Dave......I'd like to try the wrench on someone else's air supply which was known to be powerful enough.
John

Any compressor with a receiver at 8bar pressure is well beyond adequate. I'm not sure how else I can explain it.

 

[aesmith]

I believe you, as soon as I found the problem exists only in one direction it was clear that air supply isn't the issue.

 

[Burnerman]

The air pressure is completely adequate and always was......the air hose needs to supply a significant volume of air which a small diameter hose just won't do.
John

 

[aesmith]

With the thing in bits I was looking for anything not symmetrical, to try and understand why it works in one direction and not the other. The only thing I found was a rough bit on one side of the rocker, I can't really see how it would have that effect but I smoothed it off anyway. Back together it actually now works quite a lot better. It still takes a couple of tries before it hammers in reverse (and still works every time forwards). That could be just a result or everything being cleaned and oiled. Either way it's made the difference between being almost completely useless, to now usable if a bit annoying.