Some lessons learned and re-learned 2019

Discussion in 'Prony Brake' started by Jerry Christiansen, Nov 12, 2019.

  1. Jerry Christiansen

    Jerry Christiansen Mega Poster WMSTR Lifetime Member

    Hi all,

    Now that the 2019 steam show season is over, we have time to reflect on some lessons learned and re-learned.

    Lesson Number One has to do with exhaust and power.

    We all know that mufflers cause back pressure and restrict the flow of exhaust out of the engine. If we remove the muffler and 'let the engine breathe', we will get more power. Many motorcycle riders also claim, "Loud Pipes Save Lives."

    Last summer (2018) at a show a young fellow came to the Blue Brake with an H International that had a straight pipe. I don't remember how much power we measured. After the run we started talking about mufflers, back pressure, cylinder filling and power. I commented that often times engines will produce more power with a muffler than without.

    This year (2019) he brought the same H back. He had replaced the carb with one from an M and was using a K&N style paper air filter instead of the factory oil bath filter.The straight pipe was in place and he had a factory muffler with him. I thought with those two changes, maybe he will get more power with the straight pipe.

    The results of the two runs are below.

    Straight Pipe
    Pounds . . RPM . . . Horsepower
    50 . . . . 322 . . . 16.1
    53 . . . . 317 . . . 16.8
    55 . . . . 313 . . . 17.2
    58 . . . . 309 . . . 17.9
    60 . . . . 306 . . . 18.4
    62 . . . . 295 . . . 18.3
    65 . . . . 230 . . . 15

    Pounds . . RPM . . . Horsepower
    50 . . . . 319 . . . 16
    52 . . . . 314 . . . 16.3
    55 . . . . 312 . . . 17.2
    64 . . . . 313 . . . 20.0
    70 . . . . 311 . . . 21.8
    71 . . . . 302 . . . 21.4
    75 . . . . 285 . . . 21.4
    77 . . . . 267 . . . 20.6

    When he entered the tractor pull later that weekend, he was running with the muffler.

    Jerry Christiansen
  2. Ned

    Ned Mega Poster WMSTR Lifetime Member

    That's really interesting. I've always heard that having the right muffler is actually better than not. Thanks for posting the results and thanks to the tractor operator for doing the demo.

    Now the real question is would this transfer to a steamer using a spark arrestor???
    M Kerkvliet likes this.
  3. M Kerkvliet

    M Kerkvliet WMSTR Past President Administrator WMSTR Lifetime Member

  4. karl stange

    karl stange Mega Poster WMSTR Lifetime Member

    Scavenging effect at the exhaust outlet of the head helps create a vacuum in the combustion chamber, which in turn, helps evacuate the spent gases. Running a straight pipe has no or minimal scavenging effect. It will actually help draw in atomized fuel through the intake as rpm increases.
    As Ned stated above, having the correct or tuned exhaust system will gain power for the engine.
  5. Jerry Christiansen

    Jerry Christiansen Mega Poster WMSTR Lifetime Member

    Ned, Karl and anyone else,

    Yes, it apples to steam engines. Some time ago a person told me that the rail road did extensive testing with different size exhaust nozzles and nozzle height testing for power and efficiency. The steam hitting the bottom of the stack needs to fit and fill the stack. If the steam column is too wide, the steam will swirl in the smoke box and not produce good draft. If the steam column is too narrow, it won't 'seal' the stack and won't produce good draft.

    The sliding D valve usually shuts off the exhaust before the piston hits the bottom of the stroke. I believe this is to cushion the piston and act as a brake to stop the movement.

    Similar to the gasoline engine, these factors come into tune at certain rpm and load. Outside of the ideal rpm and load, the tuning isn't 'perfect'. Modern engines have variable cam timing and variable valve opening to produce the 'perfect tune' over a wider rpm range.

    Lesson Number Two Learned and Re-Learned
    A belt can only be abused so much, and then it will fail.

    Shortly after Blue Brake One was built, some one gave me a very good endless belt. At a show that first summer, someone pulled ahead after a run on the brake, turned the steering wheel and ran part way over the unblemished belt. A fellow in the New Ulm area repaired it and we have used and abused it many times. I suspect the belt is not designed to run some of the loads we have put through it.

    Last summer at Crosby, we had a belt breaking demo. None of us took a picture of the belt on the ground after it broke. Here are a couple pictures I took today.



    We were only around 100Hp, this poor belt has been over 130Hp in the past. More than likely that is a lot more than what is it rated. I need to check with the fellow near New Ulm and see if this can be repaired again. One good thing about the break, the repair done several years ago is right next to the break can be cut out. If you look carefully, you can see the repair right next to the break.

    Lesson Number Three Learned and Re-Learned

    You have probably heard the old saying, "Never look a gift horse in the mouth."
    A new saying is, "You should always look a gift belt in the splice."

    After the belt breaking demo, I needed to borrow a belt. At a show after Crosby I asked about borrowing a belt and was told, "look over in the shed, there are some good ones there."

    We picked a belt that looked as good as the others in the pile and hooked it up. After we ran up around 100Hp we stopped and found this.


    I am glad we didn't pull this belt any longer or harder than we did.

    Jerry Christiansen
    David Schoff and Seth Hanson like this.
  6. Jerry Christiansen

    Jerry Christiansen Mega Poster WMSTR Lifetime Member

    Hi all,

    Lesson #4 Horsepower for a rotating shaft is calculated by multiplying torque time rpm, then dividing by 5252.
    If an engine is not running at its rated rpm, it can not produce it rated horsepower.

    At New Rockford we got to meet Loren Larson. Loren has a Massy Harris tractor with a Chevy 283. He has headers that point straight up in the air, a four barrel carb and a cam. I believe he said the package should put out around 230Hp when the engine is in the mid 5000 rpm.

    He asked about hooking up to the Blue Brake using the PTO. We had quite a conversation about that. The Blue Brake should not spin faster than 620 rpm. The 283 would spin it MUCH faster than that. We agreed to keep the Brake at 540 rpm. Loren would open the throttle a bit, then I would tighten the Brake and bring the rpm back to 540. The results are below.

    Pounds . . . rpm . . . Horsepower
    46 . . . . . 534 . . . 24.6
    60 . . . . . 540 . . . 32.9
    73 . . . . . 540 . . . 39.4
    80 . . . . . 540 . . . 43.2
    90 . . . . . 540 . . . 48.6
    100 . . . . 540 . . . 54.0

    I was a bit concerned when we got to 54 Hp. The wood blocks on the Blue Brake start to smoke around 60 Hp when we run at 540 rpm. We had a crowd, so I figured we would go a bit farther. I asked Loren for more throttle and he said, "That is all I have."

    Loren said the tach was right around 1300 rpm when the PTO was at 540 rpm. Later, he checked the torque and horsepower curves for the cam and reported that the 54 Hp we measured was what the spec sheets said the engine should produce at 1300 rpm.

    That was sweet sound. The 283 was a full throttle with the cam and straight up headers. I wish I had a video of that so we could listen to it!

    Back to Lesson #4. An engine will not produce its rated power unless it is running at it rated rpm.

    Jerry Christiansen
    frigstad and Ray Wangler like this.

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