Hi All

I`m almost done with my power drawbar. I did all the routing of the air lines and other fittings.
I didn`t want to make the air valve as shown in the plans that I purchased from Joe Vicars.
It was basically a two position lever modified from the top of the air nut driver
I instead purchase this valve on ebay. http://cgi.ebay.com/ws/eBayISAPI.dll...m=260441342453
A hand lever valve 4 way 3 position center closed valve. Its my belief this configuration
will not work...but I`m uncertain why.

Here`s what happens. With both ports attached to the drawbar the air cylinder will run.
But the nut driver will not run. If I remove one of the feeder lines to the drawbar the nut driver will run.
Somehow there is air in the line and the system can`t bleed. I though the systen would bleed off thru the air cylinder.
Hoping someone in the forums is an expert in pneumatic.

I asked this question in another forum. Its inclusion here might help to clarify my problems.
I`ve done some searching online but can`t seem to line a manual lever valve that meets the specs
below

The air to your nut drive must be exhausted on the opposite side to make the motor run. Likewise, the opp side of whichever way you are moving the cylinder.
You really need 2 valves. These can be within the same switch body, but you need 2 spools. The first valve needs to be open center, 3/2. This will control your cylinder. The second valve can also be 3/2 open center, but you need to put a plug in 1 exhaust port.
When you flip the valve for the cylinder to go down and the motor to run, the air from the op side of cylinder is exhausted through the open center. The motor should be exhausted separately from the cylinder exhaust otherwise backpressure to the cylinder will occur. When you flip the valve for the cylinder to go up, air is directed away from the motor to the blocked port shutting down the motor.
Clear as mud?

"clear as mud" is true.

To be of any help it is necessary to know the components manufacturers name and part numbers at least. Pictures of the present hookup would lso be helpful.

Also a schematic of some sort of how the system is plumbed is the only way to make any diagnosis. Since most people don't know how to make a scematic you could make picture drawing of the way you have it hooked up so any plumbing flaws could come to light.

Most air valves have Port Numbers or Letters so make sure these show in your drawing. Usually they are 5-Ported with designations like "IN",
CYL1", "CYL2", "EXH1", "EXH2".

Without that kind of information you will only get guesses as to what the problem is and those guesses will likely use terms that you may not understand.

BTW, the Ebay link will not open for me, it may be old enough to be removed.

As the other poster mentiond it may take two valves to do waht it appears you want. If ths is a sequence of operation you may find the load that moves first using one valve is not the one that should move first.

What is a "power drawbar"? Your picture is a beautiful piece of equipment but something I've never seen.

Hi
Here is a video showing how a drawbar works. It basically allows quick changes of the tool in
a milling machine. I`ll add some pics of the hose layout asap

http://www.youtube.com/watch?v...hZfk&feature=related

Also, mark the Motor and Cylider as "A" and "B" and writeup a sequence of events:

A+, BCW, B Stall, BStop, A- is one way I've used but any kind of writeup that explains the desired motions of all actuators is necessary.

Ebay link for valve HV400-04

pdf for valve

IMO
This valve should be used for just the nut runner....an additional seperate valve is probably needed for the cylinder...as Bob said a sequence of events ,pneumatic diagrem etc is really needed to give a definitive answer.

EDIT...
http://home.insightbb.com/~joe...r3/cheap_drawbar.htm

OK ...This pic in my posted link makes things clearer...
A single acting cylinder is being used to add tension to the drawbar?
Motor spins the nut / screw ...nut/screw engages with toolholder ...toolholder is drawn up into quill taper ....as the pneumatic motor load increases / stalls the cylinder extends adding some extra force to seating the toolholder?

Or is it the other way around...i.e. the cylinder is used to push the tooling out ...then the motor spins undoing the tool holder?

Additional edit...

quote:

Here`s what happens. With both ports attached to the drawbar the air cylinder will run.
But the nut driver will not run. If I remove one of the feeder lines to the drawbar the nut driver will run.

Ummmmm shouldn't there be only ONE feeder line?...You haven't got one feeder from EACH port of the nut runner going to the SAME port on the cylinder have you?

This message has been edited. Last edited by: Woodygb,

It seems that there are two feeds.

http://www.cnccookbook.com/CCMillDrawbar.html

So...
Air is applied to impact wrench CW rotation port
The single acting cylinder extends causing the socket on the modified impact wrench to engage with the nut on top of the tooling drawbar and then the impact wrench spins ...once the drawbar is locked / tightened the air supply to the CW rotation port is removed and the cylinder retracts disengaging the socket from the drawbar ...the same happens in the CCW direction undoing the drawbar?

Is the exhaust built into the impact wrenches body and we can therefore call the two ports inlet CW and inlet CCW?
If so you could try blocking the exhaust port on your ebay valve.

This message has been edited. Last edited by: Woodygb,

Hi All

I decided not to troubeshoot the current problem. Instead I will do what
I should have done....follow my purchased plans.
I am now working with the plans I purchased. This includes making a valve
from a component that was the top of the nut driver. Today I did the layout
and milling of the part, including making a custom gasket for the new valve.
Tomorrow`s the big day, I should be able to test the valve.

Thanks to all that posted.... I thank you for you time.
Regards Barry