Measuring rotating Force

[racear]

I am attempting to build a machine to hone the cylinders of a automobile engine. I need to be able to measure the force required to hone that cylinder. I want to be able to measure the force as it travels up and down in each cylinder so that I can determine the tight spot. I tried to measure in amps and watts but I am driving thru a gear box and that measurement has not been adequate. any help here would be great as I have run out of ideas

 

[patprimmer]

Have the reaction to the shaft turning apply to a load cell, just like they do in engine dynometers.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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[MikeHalloran]

You could put strain gages on the arms that push the stones outward.
You would need slip rings to bring in power for the preamp rotating with the head, and either more slip rings or an RF link to get the buffered data off the rotating assembly for analysis. For the purpose of locating the hard spots, you'd also need a linear transducer on the ram and an angular position transducer on the rotating assembly. You could do it easily for a hundred grand, and maybe for ten grand with some creativity, less if you're willing to homebrew a lot of stuff and learn a lot of new skills and spend a lot of time doing it.

I'm guessing it's all been done before, but the answers have commercial value, so the guys who know them probably aren't talking.

Or you could start at sae.org, and search for appropriate research papers in their mountain of mud. Bring your wallet.

If your labor is worth anything, it would be cheaper to buy a commercial honing machine, or contract the services of someone who has already done so.




Mike Halloran
Pembroke Pines, FL, USA

 

[racear]

Mike: you are correct as I have a hone machine now and it measures percent load and it does it on a analog gage, but the new hone head I have built has a gear box and I tried to do the same thing but I dont pull on the motor hard enough to get a good reading. This is the way most machines work from.
Pat:Since I do have a Dynomometer, your thoughts is one that I have considered, but we are talking low ft. lbs measurement and I could not figure out how to load the shaft to get a deflection

 

[patprimmer]

Mount the entire machine so it is firm re sideways movement and controlled in vertical movement but can rotate freely when in place.

Have an arm coming off this so it rests against a stop. Put a load cell between the arm and the stop.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[racear]

I can do this except I can mount it on the AC motor and measure its force. Trying to figure what poundage transducer I will need. But you have a good idea

 

[Pancholin]

I will try to put the picture in my mind into this keyboard. The main driveshaft for the hone will have a spring loaded inner shaft that will deflect a given amount for the load of turning the hone. Attach a set of points and condenser, with a coil and fire a timing light with each turn and observe the deflection of the spring. measure the deflection with a torque wrench and install a timing mark relationship between the two shafts to determine the hone's loading. Think old Ford bendix starter drive

 

[racear]

Yes this will work and I understand what you are saying but I need readings as the hone head Reciprocated so that I know where the tight spot is. You have to understand this is happening at 40 to 60 strokes per minute. I can read this shaft deflection, that you are describing, with a rotary transducer but this is really expensive so therefore I am pursuing a cheaper alternative, if there is one

 

[yoshimitsuspeed]

I think Pancholins idea might still work if the spring was soft enough to allow a wide range of travel. Say 12:00 was light load and 6:00 was heavy load you wouldn't need a really accurate pointer.

Also if you had a long timing mark along the whole shaft so it stayed visible throughout the range of axial travel.


I could also see patprimmers concept working pretty well.

 

[Warpspeed]

You can buy rotary torque transducers.
The basic idea is usually some type of torsion bar with rotary encoders at each end.
As more torque is applied, one end lags the other, and you get a variable duty cycle digital output proportional to torque.

 

[racear]

Yes I am looking at torque transducers. I have started a spreadsheet with the different options along with cost. One is torque transducer, another is current transducer and another is load cells. If any one has other ideas , pass them along so I can take a look.
racear

 

[LionelHutz]

Have you actually used a power meter aka wattmeter on the motor instead of just measuring the current?

 

[racear]

No I have not, please educate me as this should work also. Where do I get the parts.
racear

 

[Warpspeed]

If small torque change does not show up on a current meter, it will not show up on a watt meter either.
The internal inertia of the fast spinning drive motor, and friction in the transmission, will mask small cyclic torque fluctuation in the output shaft. The motor current will be very insensitive to the indication you are seeking.

A further thought has occurred to me.
How about using a very flexible toothed drive belt, and measuring belt tension on the drive side.
The belt could be wrapped around a spring loaded idler, spring deflection would indicate load torque.
It's a bit Mickey Mouse, but at the low speeds involved, it should work if the hone only has to turn in one direction.

 

[LionelHutz]

Hmmm, no one posted that the current change did not show up, only that it "has not been adequate" which is somewhat vague. I'm somewhat guessing that the current changes but not enough to get a proper indication of the load, likely due to it being a small single phase motor that has a widely varying power factor as the load changes with the end result being a big load change is seen as a small current change.

A power transducer measures the input power to the motor and is a much better indicator of motor load. It could be a solution if the motor actually does see the load variations. Here is an example;

http://www.crmagnetics.com/products/Power-C8.aspx

You have to decide if "250 ms max. 0-90% FS" is fast enough (the response time is 0.25 seconds to change from 0 load to 90% load) and also look at finding a meter to read that output with a quick response.

 

[racear]

Ok now you have got my good ear. The motor on the machine now is a 2hp. It does not have a name plate so I will hang a amp meter on it today. And you are correct, I do have not enough current difference to be able to hone by. That is why I like the idea of a transducer so I can narrow the scale where I want and try to get the speed up to at least 200 hertz. Good idea people. Yall is my hero
racear

 

[racear]

Ok for an update. I am trying to methods of readings. I am monitoring the amp draw thru a current transducer and I have mounted a sensitive load cell under the motor. As thew belt pulls on the load cell, I generate a reading. Am playing with it to see which is most responsive and quickest.
Now for next phase, I need to monitor how much (in size0 I am removing from the cylinder bore. I really dont care about size, I just want to know how much I removed while I honed. Remember we are floating in coolant. Please bounce some ideas.
racear