Understanding torque -- impact guns and high torque drills

[Sonic]

Hi i have a question regarding torque with impact guns and high torque drills.

So i just bought a impact gun which is rated at 1000nm at 2200 rpm how can this have such high torque were my cars engine makes only 400nm at 2500rpm

So i guess my question is how can we compare these torques to each other?

To my understanding horsepower is a function of torque and rpm

So for the torque wrench if we convert 1000nm to ftlbs we get around 737 ftlbs

So rpmxtorque/5252

2200 x 737/5252

We get 308hp which is obviously incorrect so what am i missing here?

Thanks hope i made sense in my question

 

[russ_watters]

I see two possibilities:

1. The torque isn't matched to that RPM. Do you have the exact wording of the specs (a link?)?

2. Being an *impact* gun means the torque is generated by a series of impacts and is not continuously applied.

 

[Sonic]

Thanks for your reply here's the link for the impact gun

https://www.makita.com.au/products/...w1002z-18v-mobile-brushless-1-2-impact-wrench

What about for this drill you would think that the 114nm would be matched to the rpm? 114nm is still comparable to a dmall cars torque?
https://www.makita.com.au/products/...481z-18v-mobile-brushless-hammer-driver-drill

 

[russ_watters]

Thanks for your reply here's the link for the impact gun

https://www.makita.com.au/products/...w1002z-18v-mobile-brushless-1-2-impact-wrench

So, that's 2200 impacts per minute, not rpm. The rpm is listed at 1800 under no load. So it will drop as you apply a load.

What about for this drill you would think that the 114nm would be matched to the rpm?
https://www.makita.com.au/products/...481z-18v-mobile-brushless-hammer-driver-drill

No; I see the same issue there.

 

[Sonic]

Ok so with no load i will still be making 115nm in the drill correct spinning at 2100rpm?

Even if the drill spins at 300rpm underload with 115nm torque i get close to 5hp

Thats that's quite a large petrol engine in comparioson (briggs and stratton etc)

 

[Sonic]

Ok so i think i messed that up because if we assume 300rpm then by lowering the rpm would mean we no longer are making 115nm so our hp level would be lower.But i still question the max torque of 115nm can we assume that's happening at 2200rpm?

If so no load were making close to 35hp?

 

[Sonic]

I had a think about it greatest torque would be in low gear so that's rated at 550rpm much lower than the 2200.

So my calcs show at 550rpm and 84ftlbs of torque we make 8.8hp with no load does this sound reasonable for a small drill?

 

[CWatters]

No 8hp is way too high. 1hp = 750w. I think most drills are probably sub 500w.

The max torque will be the peak torque that occurs during an impact not continuously.

Edit: similar drill here is rated at 640w continuous.

http://www.powertoolworld.co.uk/makita-dlx2040tj-18v-brushless-impact-driver-combi-drill-kit-inc-2x-5-0ah-batts#gref

 

[CWatters]

PS: with no load a drill produces no output power.

 

[JBA]

Here is one simple demonstration (of many available on the web) of how impact drills operate. This is why impact drills are rated in "impacts per minute" rather than rpm.

http://www.popularmechanics.com/hom...a-cutaway-view-of-how-an-impact-driver-works/