How to Measure Power Tool Shaft Torque 7

[HydraulicsGuy]

I have a Ridgid MEGAMax Power Base:

I have found a way to make this base power-on without having one of their 3 attachment heads attached (a project in itself!). I will be using it to drive a hydraulic pump. Pump size to be chosen based on Power Base performance. Therefore, I need to know:

(1) no-load RPM
&
(2a) stall torque or
(2b) torque at some other RPM

From those, I can calculate the RPM at any torque, or the torque at any RPM.

RPM measurement should be pretty straightforward I think. This was recommended:

My question: What is a simple cheap way to directly measure the torque? I don't want to design a test setup if I don't have to. I did some brief googling but nothing stood out, other than a reply from someone on this forum on another thread, suggesting to measure a base reaction rather than a torque at the shaft. There are no shaft RPM and torque values stated for this Power Base that I could find. There are some values, but they are for the attachment heads, and who knows what kind of gearing takes place inside those. RPM + torque values (together) are extremely difficult to come by on the internet, for any power tool. I have not tried contacting the company. Since it's not the tool's intended use, I'm 100% sure it will be met with disdain. I'm also 100% sure I'll have to correspond with a salesman, and there is only a 25% chance he'll comprehend what I'm looking for. I want to discuss with engineers.

More googling after posting this. Is the answer a "torque transducer"?

 

[itsmoked]

HydraulicsGuy; Just checking, no offense meant. Do you understand that Horsepower = RPM x Torque and that by not using the motor at full RPM you're giving away 82.5% of the system's horsepower? With a gear reduction you can harvest ALL the available horsepower?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[IRstuff]

The OP just doesn't seem to understanding "gearing"

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

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[EdStainless]

LI, you have to watch the impact drivers, their peak torque is related to the impact, not steady operation.
There are a number of non-impact drill/drivers out there that deliver over 1000in-lb and run at 1800-2200rpm no load.
In these tools the torque and speed are controlled on a profile.
I talked with someone that I know that used to work for one of the tool companies. As he recalled they typically ran devices at 100% T at stall, and about 80% of that at 80% of full speed, and then it tailed off to 60% T at 100% speed. They can do this since both limits are being controlled. He said that they had a real high torque version that cost a bit more to build, and they sold it for 2.5x the price because they wanted to used by trades only. Otherwise they might break peoples wrists.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy

 

[HydraulicsGuy]

I think some of you guys don't know how to read, or to interpret what you read. In my update post a few days ago I said: "We will either have to utilize the attachment head with its ~11:1 gearing, or extract and utilize said gearing, or abandon this Ridgid Power Base idea altogether and look into another power tool motor base with lower speed / higher torque."

Here's the thing some of you seem to be missing. I didn't know the RPM of the darn Power Base before we measured it a few days ago. I assumed it was around 1800 RPM. Therefore, I thought I'd have plenty of torque. When we finally measured it to be almost 16000 RPM, I knew the torque would be low, and I was nervous about it. We were just trying to get the RPM down for the test. We can't run a pump at 16000 RPM. How many times do I have to say that? Do you guys understand the limits of hydraulic pumps? That's why we ran it at partial trigger pull, ~3000 RPM. I understand that the power won't be anywhere near its max at partial trigger pull. It was just a test to try to prove the concept, and collect some data on the Power Base. And as I said before, if you choose a pump with a small enough displacement, it can absolutely be compatible with a low-torque motor.

IRStuff, you're the guy that implied earlier in the thread that the torque should be over 1000 in-lb!

It's an 18V battery driven tool. Do a search on HD for comparable systems:

https://www.homedepot.com/p/Milwaukee-M18-FUEL-18-...

--> 1200 in-lb

https://www.homedepot.com/p/Makita-18V-LXT-Sub-Com...

"XWT12ZB - BL Brushless Motor delivers 130 ft.lbs. of Max Torque and 230 ft.lbs. of Nut-Busting Torque"

and

https://www.homedepot.com/p/questions/RIDGID-R8640...

search for torque. "RIDGID Power Tool Team" claimed 1395 in-lb, which seems consistent with other power tools sold at HD

You clearly thought the torque of the Power Base would be very high. I thought it would be much higher than it is too, because I thought the speed would be much lower.

Show me one statement I've made that indicates I don't understand gearing, or not using full capability of a motor?

 

[HydraulicsGuy]

LI, you have to watch the impact drivers, their peak torque is related to the impact, not steady operation.
There are a number of non-impact drill/drivers out there that deliver over 1000in-lb and run at 1800-2200rpm no load.
In these tools the torque and speed are controlled on a profile.
I talked with someone that I know that used to work for one of the tool companies. As he recalled they typically ran devices at 100% T at stall, and about 80% of that at 80% of full speed, and then it tailed off to 60% T at 100% speed. They can do this since both limits are being controlled. He said that they had a real high torque version that cost a bit more to build, and they sold it for 2.5x the price because they wanted to used by trades only. Otherwise they might break peoples wrists.

Thank you sir! I wonder about that every time somebody throws out an impact driver as an option. I always assumed they couldn't be operated continuously like a drill, but then I thought maybe I'm wrong because people keep throwing them out there. But I don't know enough about power tools so I keep my mouth shut on that.

 

[HydraulicsGuy]

Take apart a cordless rebar cutter to see how it is done.

http://shop.wirecutterstore.com/Diamond-Portable-B...

Too expensive my man. They'd never agree to buying this. We could maybe find a cheap used one, but it's always buyer beware. And if it was good enough to go forward with, we couldn't buy new ones at that price for every power unit we make. And who knows what's under the hood? Could be another ultra-high speed / pitifully-low torque debacle. Thanks for the idea though.

 

[HydraulicsGuy]

But who knows what the output was? If the output was only 300 RPM, then the base would run at 3300 RPM. Not too bad. Ridgid says 1400 RPM output on the rotary hammer head, but know knows? Earlier in the thread I've already pointed out some Makita numbers being all over the place and inconsistent. From what I've seen, you can't trust everything these power tool manufacturers publish.

But here's the real issue: even at partial trigger pull, there was nothing that told me that it WOULD NOT have enough torque to run a small hydraulic pump. Because I ran it at 1/5 the no-load RPMs doesn't mean it was at 1/5 the full power. Could have been 1/3 the full power. But let's say for conservatism that at 3000 RPMs, it's at 1/5 the full power. Which on a (let's say) 1.5 HP motor, would be 0.3 HP, not a lot but still enough power to run a small hydraulic pump to get to 100 or 200 psi (depending on flowrate).

What told you that it didn't have enough torque or power at 3000 RPMs (with a no-load speed of 16000 RPMs) to at least run a small hydraulic pump?

 

[IRstuff]

For the simple reason posted by itsmoked: HP = torque * rpm. You don't get anything by reducing the rpms from the trigger pull; it just reduces the overall power.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

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[waross]

Torque can be heavy. For ten times the torque, a motor may easily be ten times the weight.
Hence, 16,000 RPM and reduction gears.
Reduction gears are much lighter and cheaper than higher torque motors.
Motor specs. Brushless DC motors: Too much electronics to use data from one motor for a different motor.
The electronics may be limiting the torque. You don't know.
The rebar cutter will have a positive displacement high pressure hydraulic pump. Possibly a piston pump.
It will most likely be unusable for directly driving your pump.
Recomendations:
Use the 11:1 reducer.
Use an actual pump. The boss may not always be right but this time he may be right.
And he is always the boss.
From the start of this thread I have been thinking;
If you want to know the performance of a pump, use a pump.
Monitor the current from the battery as itsmoked suggests to avoid overloading and rapid motor failure.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

I fundamentally have a problem with this whole thing. From experience and being burned and seeing others be burned by the philosophy at play here I say don't waste your life trying to get this odd-ball power head to do anything for you. You'll go thru back breaking flaming hoop jumps to finally get this to work and Ridgid, who doesn't give a dang about you, will slightly alter their power head the week before you get an order for 20 units. Or, worse, will dump the product entirely! I have seen this happen at least a dozen times.

Shaking my head, I helped a local engineering firm using a partially hacked Amazon camera system to create a medical arthroscopic knee surgery tool. After 8 months of painstaking work they started shipping and sure enough the source camera was yanked from the market. The company promptly tanked.

Stop wasting your time and do it in a manner that allows you to use ANY power tool by picking any quality drill and chucking your hydraulic pump input shaft in it. This always gets you your needed gear reduction for free. Chucked power drills will always be available and a user can choose to use a corded tool if they don't need to move the tool around. You and your prolduct will never be "locked out".

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LittleInch]

I've gone back and read the entire thing again and I'm still stuck as to what you are really trying to do with this driver?

Is it to test the pump?
Use the pump for something?
Or just a means of discovering the torque to use for something else?

I did think about the impact bit right after posting it, but figured it was the basics - i.e. if you want to find a certain rpm and torque why not go looking for that combination instead of trying to use what is now a broken power base?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[kimsood]

Hello, hope this will help:

MEASURING TORQUE ON A SHAFT - THEORY OF OPERATION ...
Draw a line parallel to the axis of the shaft. [02:25]
Place the same gauge diametrically opposite on the shaft. [03:36]
Draw on the surface of the shaft an axial line. [05:37]
Distort an ideal square image on the surface of the shaft. [06:18]
Divide by the radius of the shaft. [07:39]
Detect the maximum strain on the shaft. [09:33]

Source:

https://www.youtube.com/watch?v=rMoRuZuYHWc

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