PICTURE -- Big vs. small impact wrench

Actually,

Actually,

A recent design combines an impact wrench and an air ratchet, often called a "reactionless air ratchet" [4] by the manufacturers, incorporating an impact assembly before the ratchet assembly. Such a design allows very high output torques with minimal effort on the operator, and prevents the common injury of slamming one's knuckles into some part of the equipment when the fastener tightens down and the torque suddenly increases. Specialty designs are available for certain applications, such as removing crankshaft pullies without removing the radiator in a vehicle.

Yes, the same setup is often used on ship engines, for example to attach the cylinder head to the cylinder.

Indeed. Often without any form of gasket.

I didn't see the show, but I have to weigh in here. A heavy recovery vehicle doesn't have tires, it has tracks. ;-)

Your statement indicating that you've never looked at the design, explains why you don't understand the actions involved, and why the rest of your theories about the tools' actions are incorrect.

The rotational direction of the striking parts is not reversed, doesn't change direction (unless the user changes the direction of the output to reverse the direction of rotation of the fastener).

The striking parts work with other parts to deliver glancing blows to the driven parts (output shaft).

BTW, the impacting action doesn't start until the fastener exhibits some rotational resistance/opposition to the tool's output (the fastener being installed becomes seated, a self-locking fastener, rusted or damaged threads, or a seated fastener needs impacting force to loosen it). However, mechanics that frequently assemble threaded parts cross-threaded, will experience the impacting action more often.

The practice of starting the fastener for the first couple of turns with just finger power generally eliminates the possibility of cross-threading the fastener.

Normally, the tool acts like a rotational driver unless a high(er) driving force needs to be applied.

Typically, some torque can be felt by the user that holds an air-operated impact wrench not attached to a fastener, and gooses the trigger to wide-open repeatedly, just to hear the tool's exaust noise. This torque is caused by the tool's air motor rotor jumping from zero/low speed to full speed, and the counter force of compressed air acting between the tool housing and the air motor's moving parts.

WB ......... metalworking projects

...You must have missed the part where I said it was more of a joke than a serious post, right? I'm not going to debate the issue when I wasn't putting myself in the position to defend it in the first place.

However, you are right. Technique and proper use / skill does mean a heck of a lot more than some or maybe even most people know.

Regards, Joe Agro, Jr. (800) 871-5022

We agree on that.

It doesn't have to be with a complicated tool, either. I knew that lesson from years of shovelling levees in rice fields, but I relearned it one summer working construction. I was told to remove the bottom three courses of a very hard concrete brick from the back of a building on which we were building an extension. The first day, it took several hours wailing with all my might with the sledgehammer just to make a hole (remember, young, 200# 6' and spent my previous summers shovelling, throwing fertilizer bags by the hundreds for the crop duster service). I got a few more out that day. The next, within 30 minutes I was removing each brick with three hits, and not using all my might but aiming better, and finished before quitting time.

Pete Keillor

And the Heavy Recovery Vehicle (M88A2) has a 1" hydraulic impact in its arsenal. The M88A1 was considered a Medium Recovery Vehicle. The M578 is a Light recovery vehicle and it has tracks too.

The 10-Ton HEMTT (Wrecker) could be considered a Heavy "Wheeled Vehicle" Recovery Vehicle and it does have large tires. The 900Series 5-Ton Wrecker would be a Medium/Light Wheeled Recovery Vehicle..

Only the M88, M88A1 and M88A2 have the 1" hydraulic impact wrench (which runs off the Little Joe APU). There is a lot of feedback to the operator with one of those. Been there, done that.

Anything else no-one wanted to know?

And that is IIRC the vehicle in question. The cameraman was _not_ a happy camper after the wheel and tire landed on him.

Yup, M88's were exactly what I was thinking of. A2 version was well after my time. According to wikipedia A1 was also "Heavy" with only the original M88 being "Medium." Maybe wikipedia needs a "fix" on that point?

I was on the Service side of S&R and S&E platoons, so I rarely went out on recoveries.

Yup, those too. Even had the "opportunity" to help change some of those tires. My faded memories seem to include 3 guys to get those HEMMT tires off the rims. I'd have sure liked to see that episode of Dirty Jobs.

There's a couple of wikipedia pages that refreshed some memories.