Measuring Horsepower with a Prony Brake

[jechrist2]

Mark mentioned a portable Prony Brake that my wife financed and I built with the help of anther friend, Peter K. The picture below shows the Brake with its "landing gear" in place. The wheels are meant to move the Brake in and out of its tailer and around a show at low speeds. This picture was taken at Peter's shop
http://www.98dodge.com/jerry/bluebrake001.jpg
http://www.98dodge.com/images/bluebrake001.jpg

Once the brake is in position the landing gear comes off and the brake sits down on the ground. The picture below is on location at the Central North Dakota Steam Threshers Reunion, New Rockford, ND

http://www.98dodge.com/images/bluebrake002.jpg http://www.98dodge.com/jerry/bluebrake002.jpg


The belt pulley is on the opposite side of the brake. To hold the Brake in place we used an A John Deere as a dead man. A chain was wrapped around the frame of the Brake directly under the belt pulley. We stretched the chain out and parked the rear tire of the A on the chain. After we tied the chain to the draw bar we were ready to do belt business.

http://www.98dodge.com/images/bluebrake003.jpghttp://www.98dodge.com/jerry/bluebrake003.jpg

The top box to the left of the red wheel contains the brains and display. One LED displays rpm of the brake, another LED displays the pounds of force on the load cell. Once an engine is hooked up and the brake is spinning, turning the red wheel clockwise tightens the brake band. When the brake band is tightened the the force on the load cell increases.

To determine horsepower the operator needs to adjust the brake and read the force and rpm. The lever arm on this brake is 5.25ft long so Torque is determined by multiplying the pound of force time 5.25ft ( T = Force X 5.25ft).

Then the formula: Hp = Torque X rpm /5252 is used to calculate horsepower
Because we built the lever arm 5.25ft long, the formula simplifies for this to
Hp = Force X rpm / 1000

By taking a number of readings of different forces and corresponding rpm, a series of horsepower values can quickly be calculated.

We will taking the Brake to a Steam Show at Makoti, ND (near Minot). I hope to get some pictures of the Brake with an engine hooked up for an update.

[Carl]

Nice machine! The only question that I have is what keeps the brake from burning up?

[jechrist2]

The brake is water cooled. The large "washer" on the side of the brake wheel is water tight. When the brake is spinning the water is about 2 inches deep inside the wheel. Fresh water is constantly added and the warmed water is removed. The valves to the right of the red wheel are for adding water. If you look closely you can see a copper pipe entering the top of the white barrel. That pipe carries the warm water out of the brake.

The "washer" also keeps the brake band centered on the wheel. The "washer" extends about 1/2 an inch above the edge of the wheel. We used white oak for the blocks on the brake. The white stuff in between the blocks is beef fat. The heat renders the fat so that the brake is constantly lubricated.

[Carl]

That is a really nifty project. I'm sure that it will be kept busy wherever you show it.

[Mark / Ohio]

Cool! I like to watch them in use especially with steam or the old John Deere's.

Here's the one they use at our local show:

http://www.steamtraction.com/article/2003-01-01

At the local show they also have a large squirrel cage fan with louvers that open and close to put a load on them.

[mbkerk]

Nice pictures Jerry!

What is that PTO shaft laying on the ground for? You don't let gas tractor guys on the brake, do you? :hide:

Seriously folks... Jerry can stop the Avery with this brake. I would have lost that bet. We do however make a little steam for him... it the wheel! You can hear the tallow (sp) sizzling!

Looking forward to more pictures from the show this weekend!

[jechrist2]

Yes, that PTO shaft is a usable item. We can run 540 PTO's. At a different show an older John Deere (I don't remember if it was a 70 or a 720) came over and hooked up the PTO. When he opened up the throtle the no-load PTO speed was about 750rpm. That was quite abit over speed.

The maximum safe speed for a cast iron wheel is 6000 surface ft/min . The brake has a 30in, 2.5ft diameter. The maximium rpm for this brake, calculted by dividing the 6000ft/min by the circumference of the wheel (3.14 X 2.5ft), is 764rpm.

Even if we had gone slightly over the 6000ft/min I suspect the wheel would not have exploded. The 6000 ft/min probably has a safety factor of 2 or better built in. Even if the "explosion speed" is double (about 1500rpm), we don't plan on running 1000rpm PTO tractors.

[jechrist2]

Hi memmurphy,

Thanks for the link to the information on your brake! I found that site before by doing a search in Excite. Knowing what the Blue Brake can stop and looking at the size of your brake wheel and belt pulley, I bet there is nothing that you can't stop!

Does the squirrel cage fan you mention with adjustable louvers have any way to measure horsepower, or is it just an adjustable load?

If anyone is interested you can see another brake that I helped build that is permanently mounted at the Rollag show. Go to:

www.Rollag.com

click on the "Exhibits" button and then click on Prony Brake testing. The gentleman standing by the Red Brake is Amos Rixsman (no longer with us) of Nashville, IL. Amos was the "God of Prony Brakes and Horsepower". He gave us some good ideas when we built the Red Brake.

[Mark / Ohio]

Hi memmurphy,....
Does the squirrel cage fan you mention with adjustable louvers have any way to measure horsepower, or is it just an adjustable load?.....

I think it has an rpm gauge on it. The louvers on the intake side open and close automatically as the fan turns. I would guess the fan to be 6 foot or so in diameter. I'd always assumed they used it just to test the engine performance under a varying load over a period of time rather than for any actual measurements. I believe T.C. Spires mentioned in the above linked article built it. I thought I had a picture of it but could not find it. Will have to get some the next time I see it. I did find this one of the pony brake I took at the local 2005 show.

http://img.photobucket.com/albums/v176/memmurphy/PonyBrake2005.jpg

[jechrist2]

Mark,

I read the articles you wrote about building your brake some time ago. The color picture is a lot better than the black and white pictures and drawings in the magazine.

By looking at the size of your brake wheel, I bet there isn't an engine around that you couldn't stop if you wanted to.

How can an engine be and still run your brake? We tried running the Blue Brake with a 1.5 to 2.5 IH engine, but it didn't work. The brake was cold when we tried. Maybe if the brake was warmed up that small of engine could work.

Jerry

[Mark / Ohio]

Mark,

I read the articles you wrote about building your brake some time ago. The color picture is a lot better than the black and white pictures and drawings in the magazine.

Bruce Babcock wrote the article. Mr. Babcock and T.C. Spires were the ones involved in building the brake. I don't know either of them personally. I was just a spectator at the show when I took the photo. :)

By looking at the size of your brake wheel, I bet there isn't an engine around that you couldn't stop if you wanted to.

How can an engine be and still run your brake? We tried running the Blue Brake with a 1.5 to 2.5 IH engine, but it didn't work. The brake was cold when we tried. Maybe if the brake was warmed up that small of engine could work.
Jerry

I've never seen them run anything other than a farm tractors on the brake that I would guess to be in the 20-40 belt horsepower range. They don't have steam power at the local show anymore. They seemed to stop showing them about the time that traction engine exploded at a show in Medina, Ohio. So I suspect the reason why might be insurance or safety code issues but I never asked any of the members about it.

[jechrist2]

The pictures of the Blue Brake in the previous pictures show the Brake in Phase Two. Phase Three has now been completed.

Some of the changes are difficult to see. The brake wheel started its life as a belt pulley. During initial construction we did not cut the crown off the wheel and tried to cut the wood blocks to match the crown. Let us simply say that didn't work so well. The wheel is now flat, the crown is gone and the new blocks have a concave cut in them to match the curve of the wheel.

http://i170.photobucket.com/albums/u249/jtchrist/rollag/Blue09.jpg

Here you can see the difference between the old style block and the new. The dark one on the right shows the concave that was supposed to match the crown. The new one on the left shows the concave that matches the curve of the wheel.

http://i170.photobucket.com/albums/u249/jtchrist/rollag/Blue11.jpg

When we hooked up 540 PTO shafts before, the shaft was held on the brake with a through bolt. The splines cut in the shaft work much better than that! We will be able to hook and unhook much quicker and easier.

http://i170.photobucket.com/albums/u249/jtchrist/rollag/Blue14.jpg

The coolant removal system looks alot like it did before. This time the copper pipe is 1 inch instead of 3/4 inch. The water should get in and out quicker to keep the brake cooler.

http://i170.photobucket.com/albums/u249/jtchrist/rollag/Blue19.jpg

Here it is, Phase Three of the Blue Brake with an M International hooked up to test the improvements. Notice the feet are gone. The frame now sits right on the ground. That allows the PTO shaft to run pretty straight.

We didn't try to measure the maximum power of the M. All we wanted to do was run in the blocks and check out how well things worked. We did get up to 35Hp. The brake worked well. Between a straighter drive shaft, the frame sitting on the ground and the new blocks, the brake ran very smooth. The scale did not bounce much and was easy to read. It will be interesting to hook up a John Deere and see if the scale reading is as steady with an odd firing engne instead of the International.

Jerry Christiansen

[Mark / Ohio]

Looks like your ready for the coming season Jerry. :thThumbsU

I always wondered about the two cylinders and how that vibration effected the connected equipment. I suppose the belt would absorb some of it. That's got me to thinking. I'm trying to recall if JD had a drive shaft coupled PTO on any of the two cylinder models. Might be wrong but I don't think they did, did they?

[mbkerk]

That's got me to thinking. I'm trying to recall if JD had a drive shaft coupled PTO on any of the two cylinder models. Might be wrong but I don't think they did, did they?

Sure they did Mark! My model B has a PTO, as did all of the GP's (A, B, G, and most of the D's.)

My Model R does not have a PTO, and I am told that they were not a good idea on the R anyway. The power was not smooth enough and they would destroy either their own PTO, or the equipment they were tied up to.

[Kbeitz]

Watch that fat around the bears... If you store that machine in my barn the bears would eat it...

[jechrist2]

Watch that fat around the bears... If you store that machine in my barn the bears would eat it...


We are lucky that birds are the biggest critters around here that eat the fat. The Red Brake at Rollag sits out year round. The birds have pecked away some of the wood as they have gone after the fat.

So far we have enough poison in the shop that we haven't seen mouse activity when the brake is inside.

Jerry

[Mark / Ohio]

Sure they did Mark! My model B has a PTO, as did all of the GP's (A, B, G, and most of the D's.)

My Model R does not have a PTO, and I am told that they were not a good idea on the R anyway. The power was not smooth enough and they would destroy either their own PTO, or the equipment they were tied up to.

Oh Ok, I was suffering some brain freeze. :fing20: Here's one of my own photos taken in 2005 that shows a rear PTO shaft. :fing32:

http://fairfield_co_weather.tripod.com/AntiqueTractorShow/2005/IM000499.JPG[/url]http://fairfield_co_weather.tripod.com/AntiqueTractorShow/2005/IM000499.JPG

[jechrist2]

Hi all,

All though some people may not believe this, I am concerned about safety. I am especially concerned about safety when I am the one that might get hurt!

When I had the M hooked up to the Blue Brake (shown in Post #12) there was no shield on the PTO shaft other than the plastic cover that comes on them from the factory. I wanted a method to contain the shaft if the universal joint failed or if the shaft came uncoupled from the Brake. If you take another look at the Brake you will see that the Brake operator stands right next to the PTO shaft.

I also wanted a method to cover the spline on the end of the shaft when a tractor is hooked up to the Brake with a belt. I had some ideas of a cover on a hinge that would lift up for access that would also have a strap across the bottom to contain the shaft. All of those pictures got big, clunky and ugly in my mind.

Two interchangeable shields have now been made. One is simply a cover to prevent things from getting caught in the spline and wrapped up. The other is to keep people away from the u-joint and provide a "containment" when the PTO shaft is in place.

Here are two pictures of the cover.

http://i170.photobucket.com/albums/u249/jtchrist/rollag/Blue20.jpg


The loop just behind the block that holds the sheild is a place to hook a chain so that a fork lift can us a sling to lift the Brake. Now that the Brake sits on the ground, a fork lift can't get underneath it to pick it up.

http://i170.photobucket.com/albums/u249/jtchrist/rollag/Blue21.jpg

Here are a couple pictures of the containment device when running a PTO shaft.

http://i170.photobucket.com/albums/u249/jtchrist/rollag/Blue22.jpg

http://i170.photobucket.com/albums/u249/jtchrist/rollag/Blue23.jpg

I chose to make two different shields because I thought the PTO containment device was kind of ugly and I didn't want it sticking out in the way all the time. Maybe I will decide that switching between the two is a pain in the neck and toss the smaller one in the scrap iron barrel.

Later,
Jerry