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Looking for a dynamically balanced steel roller/drum

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  • Looking for a dynamically balanced steel roller/drum

    I am looking to find someone who could build a set of dynamometer rollers for me. They would have to be balanced for smooth operation at 4500rpm. Mass is not important, but heavier is marginally better. I don't have prints yet, but I can sketch some up with appropriate GD&T.

    Rough dimensions: 30" long and 14-18" in diameter 1/2"-1" wall thickness tubing. There should be some type of hub on each end. Possibly laser or watercut with 5 or six spokes and a 4" diameter pattern for the prop shaft. The hub will be welded to the tubing. The whole assembly should be balanced.

    I would need two. Anyone have the equipment to do this type of work? Cash paid. Obviously I will need to draft prints, but I figure it would be better to know what process you will use to manufacture, as the design is flexible and I would appreciate input to make the design easier to fabricate.

    Someone local to IA, IL, MI, WI would be prefered, but I can pay shipping.
    If the women don't find ya handsome, they should at least find ya handy

    https://www.facebook.com/WDHSTechClub

  • #2
    I got the equipment and most if not all the material and it's a fairly regular job for me,but don't have the balancing equipment.
    I just need one more tool,just one!

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    • #3
      Sounds to me like a truck trailer axle and wheel set with the right size of pipeline sections welded to the wheels would work.
      Free software for calculating bolt circles and similar: Click Here

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      • #4
        Go totally redneck and use one ton drive axle with short wide wheels AND tires, spool or weld the spiders, then drive dyno off pinion. Cheap and balanced at any tire store.

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        • #5
          Did you guys miss the 4500 rpm part?
          I just need one more tool,just one!

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          • #6
            Ask a local electrical shop that specialises in re-winding and balancing large electric motors as by definition they will have a dynamic balancer for the speed range you require.

            The welding will need to be pretty neat and consisitent (for minim metal removal during balancing.

            The drum periphery will need to be finish-machined as well - for obvious reasons.

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            • #7
              18" dia spinning 4500 rpm. Isn't that in the ballpark of 240 MPH or did I screw up my math?

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              • #8
                Did you guys miss the 4500 rpm part?
                No. The bearings are good for it.
                Free software for calculating bolt circles and similar: Click Here

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                • #9
                  I assume he wants to make a drive over vehicle dyno (can't think of correct name) so larger diameter rollers mean lower rpm. (The necessarily deeper pit or taller structure is a drawback.)

                  Just throwing out ideas, makes no difference to me.

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                  • #10
                    Originally posted by Boostinjdm
                    18" dia spinning 4500 rpm. Isn't that in the ballpark of 240 MPH or did I screw up my math?
                    Looks like you are right

                    dia 18 in
                    cir 56.54866776 in
                    rot speed 4500 rpm
                    linear speed 254469.0049 in/min
                    linear speed 4.016240608 mile/min
                    linear speed 240.9744365 mph


                    Most chassis dynamometers are rated for 200mph. 14" would get me in the 185mph range, 12" would be 160. I will probably go with twelve. I also think I am just going to build a motorcycle dyno for now. So the roller only has to be 6-12" wide, and I would only need one.
                    Last edited by Ggerg1186; 02-11-2012, 09:21 AM.
                    If the women don't find ya handsome, they should at least find ya handy

                    https://www.facebook.com/WDHSTechClub

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                    • #11
                      One of the tough parts about dynamometers is matching the torque and power of the engine to the torque and power of the dyno. At work we often have to use 600+ Hp dynos on 250hp engines. The diesel engine makes 250 at 1800rpm, but the dyno will only absorb 600hp at 4500 rpm. When you move down the dyno torque curve it has to remain above the engine torque at all times, or the dyno will slip.

                      This is the torque curve for my absorber:



                      The reason why I am going to stay away from a car chassis dynamometer, for now, is to prevent the engine torque from exceeding the dyno torque. For the same reason we use 3X dyno power above, If i strap a 500hp car to this absorber the car torque curve will not likely match the dyno torque curves, and that will cause problems.

                      The faster I can spin my dyno for a given engine speed the more power I can absorb. Larger diameter is also good to prevent some R1 owner from locking their bike in 6th gear and grenading my dyno.
                      If the women don't find ya handsome, they should at least find ya handy

                      https://www.facebook.com/WDHSTechClub

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                      • #12
                        So why not just go buy a used Dynojet dyno?? They've been around for close to 20 years now, their has to be used ones out there. Once you have the mechanicals the data collection is easy.
                        Trust me, been down this road, check my signature. It's one thing to DIY something that you can't get anywhere else, but re-inventing what someone else has already done seldom makes sense in the long run, especially when it has the potential to be extremely dangerous, or at least very exciting, when and if it comes undone.

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                        • #13
                          Originally posted by tdkkart
                          So why not just go buy a used Dynojet dyno?? They've been around for close to 20 years now, their has to be used ones out there. Once you have the mechanicals the data collection is easy.
                          Trust me, been down this road, check my signature. It's one thing to DIY something that you can't get anywhere else, but re-inventing what someone else has already done seldom makes sense in the long run, especially when it has the potential to be extremely dangerous, or at least very exciting, when and if it comes undone.
                          I am scouring the internet for some mass produced rollers, just haven't found a set for under 10 grand yet. I will keep looking.

                          Look at the rollers on this thing:




                          Actually, the mechanicals are easy for me. What is tough, is data aquisition. While I can pretend to be an electrical engineer once in a while, computer programing is a black art. I would love to pick your brain about software, speed sensors, etc. Also, keep in mind this isn't for the 5-10hp project I am still working on. I have one of these sitting in my garage I want to put to work:

                          Last edited by Ggerg1186; 02-11-2012, 10:43 AM.
                          If the women don't find ya handsome, they should at least find ya handy

                          https://www.facebook.com/WDHSTechClub

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                          • #14
                            Quite awhile ago now, but i remember seeing the rollers at the NHRA nationals at Indy.
                            They used these to push the Top Fuel Dragsters onto to start them, it was an interesting site to see, and one had to be sure their ears were covered when these things started. This eliminated the time consuming chore of push starting each one, so once they fired up on the rollers they then pulled around and into the staging lanes.
                            Set low at ground surface i think those rollers were about 18 inches in dia., and also set in the pit was the drive system which was a Chrysler Hemi engine.

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                            • #15
                              Originally posted by Ggerg1186
                              Actually, the mechanicals are easy for me. What is tough, is data aquisition. While I can pretend to be an electrical engineer once in a while, computer programing is a black art. I would love to pick your brain about software, speed sensors, etc.

                              I was in the same place, so I went looking for someone to help. IMO opinion there is one place to go for dyno data aquisition:
                              http://performancetrends.com/dtm-dyno.htm

                              While more than $24.99, I think that you'll find the pricing very reasonable when you realize what goes into a useable system. Yes, it will do more than 5-10HP. The bare bones base package could easily be applied directly to the large Dynojet rollers in your picture, or a 3" flywheel for an RC dyno.
                              Either could be set up and running in an afternoon.

                              Call and talk with Kevin, ask him who first applied his "datamite" data aquisition system to a dyno.

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