using hammers with strap wrenches

This is more a physics than a metalworking question. I'm wanting to unscrew the fan clutch and fan from the water pump
pulley of my car. I have a "striking" wrench to fit the big nut on the fan clutch and can clamp the drive belts to restrain the pulley from turning. The belts will probably hold 50-100 ft-lbs of torque, which is unlikely to be enough to free the nut. To what extent will torque from the belts (what I'm calling a strap wrench) add to the torque imparted by a sharp hammer blow to the striking wrench?
At first glance, I expected the restraining torque supplied by the belts to add to whatever torque the hammer blow furnishes, so that applying 50 ft-lbs with a cheater bar and then adding a hammer blow worth, say, 200 ft-lbs should give me 250 ft-lbs on the nut.
On more careful thought, the belts are very elastic compared to the striking wrench, leaving only the inertia of the pulley to restrain rotation. What if any role does the torque applied by the holding mechanism (belts) play in the torque between nut and pulley?
It's still useful to preload the wrench, just to keep it in place, but it's not clear the preload will add to the torque between the nut and pulley.
Has anybody worked this puzzle out accurately?
Thanks for reading,
bob prohaska
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On Thu, 25 Oct 2018 01:02:04 -0000 (UTC), bob prohaska

Absolutrly none. Torque is twisting force. You are applying the torque with the wrench against the retraint if the belt. The only "add" you have is the impact force.
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wrote:

It may enhance the crushing force, though. On an oil filter, that's bed. On a solid piece, it likely won't matter. But I'd think that most of the force would be absorbed by the belt stretch, negating it. If it's a chain, it may actually help. That's my SWAG.
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On 10/24/2018 06:02 PM, bob prohaska wrote:

The hammer blow will add its 200 ft-lbs, and will remove the cheater bar's 50 ft-lbs at precisely the same time.
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On Thursday, October 25, 2018 at 2:39:46 AM UTC-4, Great Pumpkin wrote:

Well yeah, but the impact will also tend to "shake things loose". I have re moved some pretty stuck things by applying a wrench with cheater bar and th en smacking the part itself (not the wrench) with a hammer. *
If it's simply a matter of torque on the nut (as implied in the original po st), I'd be thinking about a longer cheater. 50 ft-lbs is not very much - t hat's a 10 pound tug on a 5 foot bar.
* BTW, the 25" 1/2" breaker bar from HF takes a surprising amount of punish ment without failure. I used one on a 7/8" bolt (steel into aluminum) that was seized up tight. I added a 5-foot pipe on the end and had a big guy (tm ) leaning hard on it. I fully expected the swivel joint on the bar to shatt er, but it held while the bar itself flexed a good amount. Smacking the end of the bar (where the socket was) with a hammer caused the bolt to pop fre e (loudly). Thank the spaghetti monster that it didn't break.
It went back together with plenty of anti-seize and new bolts.
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I think it's probably correct that the hammer blow will mostly unload the cheater, not add to the torque on the struck wrench. My limitation is holding torque, not cheater advantage. The pulley to be held has no lugs that can be caught with a bar or wrench. I can put a clamp on the belts to keep it from turning, or take the belts off and buy a strap wrench, but either way the hold is limited and rigidity is poor.
The wrench I'm using is a Lisle, the 47 mm size in this set: https://www.lislecorp.com/specialty-tools/pneumatic-fan-clutch-wrench-set They claim no holder is needed, but that assumes a good air hammer.
Not having an air hammer (nor a suitable compressor) I'll try an old Skill 732 Rotohammer with a concave drift to stay on the wrench. Not as good, but the best I have.
Thanks to everybody bob prohaska

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On Thu, 25 Oct 2018 17:52:15 -0000 (UTC), bob prohaska

Make the best purchase of your life and buy a corded electric 1/2" impact gun. My $58 canadian (on sale at Canadian Tire) unit will torque over 300 lb-ft
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Is it a hammer, or a wrench? If it's an electric hammer it might help; the geometry is wrong for an impact wrench. The electric hammer I have is also a drill, and it's rather unwieldy.
Maybe I should just think of this as an excuse to buy a compressor....
8-)
bob prohaska
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On Fri, 26 Oct 2018 00:13:10 -0000 (UTC), bob prohaska

It's an "impact wrench" does the same thing as an air impact, but I find it more "agressive" than the pro model air impact wrenches I used as a professional mechanic (mine was a CP734 - but the Snap-on and MAC units were very similar. The electric is a bit bigger and heavier than the air unit, but the cord is less unwieldy than an air hose.
I use the electric impact for seasonal wheel changeovers. VERY easy to seriously overtorque the wheel nuts - - - -
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On Fri, 26 Oct 2018 00:13:10 -0000 (UTC), bob prohaska

Bob, the $149.99 21gal iron sleeved aloonimum motored HF compressors are great, if noisy. Mine's over a decade old and has just recently developed a slow leak in the unloader tube, I believe. Haven't torn it down yet. All I do is plug it in and change the oil occasionally. 2.5hp on 120v? Iffy, but sturdy little things. Anything smaller won't run an impact well for more than a few seconds. 61454 https://is.gd/iKU7kK $175 on sale for $150. Go for it.
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I still haven't fully exploited the tools I have.
To that end, I rigged up a 1/2" pipe drift on my old Skill 732 and got it solidly on the wrench. The pipe mushroomed. Looks like the next step is to get a 9/16" hex key and make a drift out of that. I'm fairly sure it won't mushroom if I preserve the temper. Keeping it seated on the wrench will be the hard part, maybe a notched sleeve will work for the few seconds required.
A compressor would be nice to have but I've managed without one for many years. A small 2 stage would be tempting if I could find a used unit. It'll probably have to live outdoors, so I don't want anything new or pretty. The garage is already a bit crowded.
Thanks for reading!
bob prohaska
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On Sat, 27 Oct 2018 02:19:42 -0000 (UTC), bob prohaska

Remove the Rad and put the impact wrench on it. You've already wasted WAY more time that it would take to pull the rad and do the job and exerted more energy scratching your head trying to figure it out.

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wrote:

My _1/4"_ 14.4v Bosch and 18v lithium Makita impactors will both remove the lugs from my Tundra. Their 1450in/lb of torque has each twisted several 1/4" hex to 1/4" square converters in half. Ditto the 1/4" hex to 1/2" square converter.
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On Fri, 26 Oct 2018 17:41:45 -0700, Larry Jaques

That IS over 100ft lbs - almost 121 actually. WOW - who'd a thunk it????
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On 10/25/2018 10:52 AM, bob prohaska wrote:

And when you finally give up, you may find the threads are LEFT handed. Paul
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wrote:

+1
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Fortunately, the threads were known from the outset to be left-hand.
A better-crafted drift proved sufficient to let the old Rotohammer break the nut free. The first try used a short length of 1/2" pipe for the drift, placing all the load on the annulus. Replacing the pipe with a pipe plug sculpted to fit the striking saddle on the wrench improved momentum transfer enough to move the nut.
I should perhaps have explained that the car isn't a daily driver and there's no need for haste in fixing it. It's more important to conserve money and physical labor.
Thanks for reading,
bob prohaska
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