a little off-topic: remotely operated impact wrench

Rigger,

In this application the 1"-8UNC grade 5 bolt is under compression. But for tensioning the bolt to its recommended pre-load a tightening torque of 480 ft-lb, lubricated, is specified in the appropriate literature. Thusly I believe I am safe.

Should it break or deform we'll replace it with a grade 8 bolt.....

1/8" or one turn should suffice to move the mechanism from "clamped" to "loose".

Wolfgang

rigger wrote:

[...]

Sorry, meant "cover plate" there.

I've used Gast air motors successfully in the past for various applications so checked their site and found this:

Following some suggestions there you could use an air driven gear motor and regulate the "tightening" air pressure to a lower level than the "loosening" air pressure to get the "unlocking" advantage you need. Perhaps check with Gast to find out if the gear reduction is high enough to hold the clamp in case of loosing air supply.

This would be easy to design, mount and plumb, especially compared to an air tool (as always imho).

dennis in nca

Another brain fart! The 1500 lb force @ 300 ft-lb torque should of course be 18,000 lb force. Factor of 12 problem....converting ft-lb to inch-lb in the torque/tension formula.

Wolfgang

snipped-for-privacy@hotmail.com wrote:

Rigger, I like this idea a lot. Will call them on monday.

There are now several workable ideas here; the most cost-effective wins! I'll have to rely on my fabricator to give me his price to put it together.

Wolfgang

rigger wrote:

Or spring load (big springs) the air cylinder so it requires air to pull the clamp loose.

Thats fairly common and if the air supply fails..it fails "hard"..clamped.

Gunner

"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences."

- Proverbs 22:3

Large pneumatic rotary actuators are readily available. A vane type would work if you can live with less than 1 turn, e.g.,

makes large vane actuators as well.

Or rack and pinion for more than 1 turn...

If you've got room, a pair of large opposed air cylinders connected by a length of roller chain wrapped around a sprocket could work. Or a single double rod cylinder, at the expense of a second turning sprocket.

One downside to any of these schemes, compared to an impact tool, is I think you'd want at least one side of the system to be air over hydraulic, else you may get some nasty banging when the nut breaks free on the loosening cycle.

IIRC, ARO and Desoutter used to make impact tools that were meant to be incorporated in automated assembly systems. It looks like they've been swallowed by IR and CP, respectively, and nothing familiar popped up in a quick search, but someone has to be making a bolt-in solution. Time to search the Thomas Register?

Ned Simmons

for tensioning the bolt to its recommended pre-load a tightening torque

of 480 ft-lb, lubricated, is specified in the appropriate literature. Thusly I believe I am safe.

Should it break or deform we'll replace it with a grade 8 bolt.....

----------------------------------------------------------------------------------

OK I have been trying to follow this thread. The impact gun I feel is impractical because have you ever tried to get a impact gun to back out

1/8 to 1 turn of a bolt. Unless you can use a delimiter to switch off air when the limit is reached in both directions. This may be a little late since you are trying to modify a recent change but will a air disc brake from a semi be suitable. Hooked up like an emergency brake... pressurized brake clamps and line lock engages..to release clamp release line lock..if system loses pressure when locked caliper stays locked until line lock is released. link to air brakes ?p=ADB225

Brake torque: 212,500 inch pounds

just a couple of thoughts

Disk brake? Why not use the caliper from an airplane disk brake? I bet they can be gotten from airplane boneyards in good condition, but not good enough for use on airplanes anymore. Or an automotive brake caliper. The rotors on my Volvo 850 look to be about 0.5" thick. An air-to-hydraulic converter could supply the pressurized fluid.

I think I recall that there were industrial disk brakes offered as well.

Joe Gwinn

Let me butt in again...can you lose the bolt and generate the clamping with something like this?

or

I'd estimate the force from the 1-8 bolt with 300 ft-lbs applied at around 15 tons, taking a SWAG of 30-40% for the screw efficiency.

Ned Simmons

On 16 Sep 2006 09:17:29 -0700, with neither quill nor qualm, snipped-for-privacy@hotmail.com quickly quoth:

I wrote "several hundreds OR thousands", Wolfgang. Big difference. ;)

That's cool.

"Perhaps the 'brew' thing bothered me" said the AAer. ;) But, you wrote it like a kid who wanted us to do his homework for him. Most folks looking for additional tips usually say what they've tried or thought of so far, but I didn't see that from you. Whatever. C'est la vie.

You could always try a pneumatic motor (air ratchet + allthread?) and pneumatic limit switches.

========================================================= Save the Whales +

the whole set! + Website design and graphics =========================================================

Okay, so I'm late and catching up, but Gunner wrote on Sat, 16 Sep 2006 17:49:09 GMT in rec.crafts.metalworking :

"Fail safe" is the idea, as opposed to "Fail Deadly"

My understanding is that Westinghouse first used air pressure to push brake pads onto the railroad tires, until something convinced him it would be better to do it the other way around.

I don't think that it's that simple. I think all rail airbrake systems use air to push the brake shoes onto the wheels. Westinghouse might have originally used the brakepipe air to do the pushing and then went to a system that used a reservoir on the car to supply the brake cylinder air pressure.

There might have been some early systems that used vacuum to move the brake cylinders, but not that Westinghouse worked on.

True enough. Hence the term of art...Fail Hard. It gets used interchangably around the erl patch in dis neck o de woods for fail safe.

Gunner

"If I'm going to reach out to the the Democrats then I need a third hand.There's no way I'm letting go of my wallet or my gun while they're around."

"Democrat. In the dictionary it's right after demobilize and right before demode` (out of fashion).

-Buddy Jordan 2001

No. Not on trains. I don't know anything about trucks.

From Wikipedia:

"If the pressure in the train line is lower than that of the reservoir, the brake cylinder exhaust portal is closed and air from the car's reservoir is fed into the brake cylinder to apply the brakes."

Whole article:

Any railroad rulebook will have much discussion about the importance of securing handbrakes if cars have to sit any length of time while not connected to the train brakepipe.

There is something of a redundancy in that the train and the locomotive each have independent braking systems, and there is a failsafe feature in that the brakes go to a full emergency application if a derailment or broken hose cause the sudden loss of brakepipe air.

Hey Carl,

Partly correct. Air under pressure is used to both release the brakes under running conditions, and to apply the brakes under running conditions, and also to "lock" the brakes when "disconnected", at least until further manual operation.

Have a peek at:

I did not read it all, but the simple explanation, starting from a completely empty system, (brakes NOT applied via air pressure) is that:

1. Air in the 100 PSI range is pumped from the engine compressor through the engineers brake-valve (located in the engine) and into the brake-line to each car ( those 3" rubber hoses between cars). The brake-line is common to all cars hooked to it.

1. The air enters into the "triple valve" on each car. This was Mr. Westinghouse's invention.

2. The triple valve diverts air into a "double-acting" brake cylinder on each individual rail-car,

4 One side of this double-acting cylinder is always in communication with the brake-line along the length of the train.

1. The other side of the cylinder has both a spring return and a reservoir tank (maybe 40 gallons???). This side of the cylinder also has a non-return valve as part of the triple valve, so pressure can not back-flow into the brake-line.

1. As the pressure on both sides is now equal, the spring overcomes the side without the spring and moves the piston to one end, causing full release of the brakes. Brakes are said to be "pumped off" (released) at this point.

2. Air continues to be pumped into the brake-line until a pre-determined point (maybe 80 PSI).

1. The "train" is now free to move.

2. To apply braking, the engine brake-control valve is set to vent air from the brake-line. This is normally done in a staged procedure in roughly 5 pound increments, with a light application being 5 pounds, and a heavy application being 30 pounds. So, assuming the initial pressure of 80 pounds, the 5 pound reduction/application will allow the brake-line to be reduced to 75 pounds, and the 30 pound one will allow the brake-line to drop to 50 pounds. (Emergency application would be to open the brake-line to vent all the air, so the brake-line pressure is "zero".)

1. These staged reductions cause an imbalance with-in the car cylinders. The imbalance allows the end with the now higher pressure to overcome the end with the now reduced pressure and to move the piston to a point of equilibrium again vis-a-vis the train line pressure as reduced.

2. The end of the cylinder with the now higher pressure (and also with the check-valve and reservoir) is easily able to overcome the spring pressure and force the piston towards the other end. The motion of the piston rod applies the brake force to the shoe on each wheel via a system of mechanical linkage.

1. To release the brakes and continue on, the engineer moves brake valve lever to a position that allows the brake-line to charge again to 80 pounds, and so the brakes release as the brake cylinders reach equilibrium again. The reservoir is of course recharged at the same time too, ready to go again.

2. If the brake-line fails, or the engineer calls for maximum reduction, or the brake-line opens for some reason such as in un-coupling, the brake-line is "dumped", that is all the air is released, and the brakes on each car affected will go to full application. If the train was in motion when this happened, this is an "Emergency Application".

The actual operation is much more complicated of course, but this is the way it works.

Take care.

Brian Laws>IIRC, all modern air brake systems use air pressure to hold the brakes _off_

Hey Brian,

You wouldn't be related to Gene Lawson would you? He was a longtime engineer on the now defunct Milwaukee Road and a good friend of my dad.

He left a great photo collection of the railroad:

Hey Jim,

Not that I know of. I have to state it that way, because I met a first cousin from western Michigan I never knew, or had even heard about, until I was into my 60"s!!!!

But pretty sure the answer is, no, not even with the "6 degrees".

I did work on the CNR in Hamilton and Toronto for three or four years in my 20's. My maternal grandfather was an engineer on the Wabash running from St.Thomas either to Windsor or Fort Erie. And my brother is an engineer, still and for the past 30 or so years, with BC Rail (recently taken over by CN) mostly at Williams Lake, BC. He was friends with the crew that had a run-away accident near there a few months ago, killing two of the three, probably due to CN's lack of understanding north-south mountain operations. It's not at all like "crossing" the Rockies east to west.

At the moment, he is running something called the "Rocky Mountaineer", some sort of a newish tourist train. Some of the cars are dome-style scenic coaches. My guess it is going to have something to do with the

2010 Olympics.

And my "hobby" is scale live steam locomotives, although I've spent damn little time doing that since I retired!!

Ohh....and Thanks for the picture pages. Very nice. Black and white is soooo much nicer than colour for rail photos!!

Take care.

Brian Laws>Brian Laws>