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15 HP RPC Build

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  • Tundra Twin Track
    replied
    After Spring Seeding is done I will setup a Idler Motor with Pony Motor equipped with centrifugal clutch just for kicks and curiosity.I will post my results and call It
    Myth Buster lol!

    Leave a comment:


  • nickel-city-fab
    replied
    Dunno about the soft start, but if Lakeside has the experience then I'd go along with that.

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  • Doozer
    replied
    Does/has anyone made a soft start RPC ??

    Leave a comment:


  • The Metal Butcher
    replied
    Originally posted by metalmagpie View Post
    You are the designer, so you get to build what you want. But I'm telling you, you do not need a clutch. The pony motor, once powered off, just spins happily for as long as the RPC is running. No reason not to KISS.

    The main reason to use an idler is to reduce the enormous surge startup current that flows through a Fitch Williams-type start capacitor network. Using an idler makes sense. Again, you can build whatever you want but my 15hp RPC uses a 3/4hp idler with no clutch. No belts squeal when it starts, it just spins right up.

    Disclaimer: I am the guy with the RPC designed by lakeside53. I can absolutely verify that it has been working for quite a number of years now. I can also tell you that when it comes to things electrical there is wisdom and there is wisdom. In other words, 10 people might chime in on a topic but only a much smaller number have any real deep knowledge of the subject. Lakeside53 is a person to pay attention to. Trust me.

    Here are some details from my build: to keep things as quiet as possible, my RPC sits on a rubber mat. Further, the idler motor has thick rubber "washers" it is mounted on. These are trivial touches, but quieter is easier to live with. Second, my RPC is in a small machinery room attached to the end of my shop which is under my house. Also in that room is my boiler and hot water heater. That room gets noticeably warmed when the RPC is running. In the winter, I take advantage of this by opening the machinery room door to let the heat in. In the summer, I use a small exhaust fan to blow the heat outdoors. Again, these are trivial matters but the end result is I don't have to heat my shop, and that's a big deal. (I'm in the Seattle area which has fairly temperate winters.)

    Another small touch that I continue to appreciate was adding 3 voltmeters showing the leg-to-leg voltages. Here's a not-so-great photo:

    It's very gratifying (and cool) to see all 3 meters reading very close to 240VAC. Means the balancing caps are working.

    If you are curious about the actual elements of my design electrically, lakeside53 already published the schematic above. I did make one change since then - I changed the output fuse block from 30A fuses to a 40A 3-pole breaker. I have several pushbutton stations around my shop. To turn on my RPC I just push the START button momentarily and that's it. The timer relay shuts off the pony motor after long enough for the idler to be up to speed (we chose 2 seconds). Dead easy. Reliable. Simple.

    metalmagpie
    Ok. Well. I'm hard headed, but not that hard headed. Advice here has been overwhelmingly one sided. Ditch the clutch, idle the pony, or stick with caps.

    Roger that.

    I like lakeside's design. I will be paying attention to it. I was planning to draw my own schematic, but with the clutch dropped, well... I may not need.

    We did rubber on Dad's as well. I will have rubber, but I also intend to have it outside, so I don't have to hear it or pay to cool it (AC).

    I love the voltmeters and intend to do the same. Maybe not immediately, as they aren't free and that money will be earmarked for more immediate shop needs, but I will leave wires and room for them for sure.

    Thanks for the post magpie.

    Leave a comment:


  • J Tiers
    replied
    A clutch could work. But it would be simpler to just either let the belt come off after starting, or allow the pony to spin with the idler. Less fussing.

    A clutch would need some careful selection of engagement speed, type, torque capability, etc. What works for a snow thrower may not work for a pony motor.

    But a pony and belt will indeed just reliably work.

    Leave a comment:


  • metalmagpie
    replied
    You are the designer, so you get to build what you want. But I'm telling you, you do not need a clutch. The pony motor, once powered off, just spins happily for as long as the RPC is running. No reason not to KISS.

    The main reason to use an idler is to reduce the enormous surge startup current that flows through a Fitch Williams-type start capacitor network. Using an idler makes sense. Again, you can build whatever you want but my 15hp RPC uses a 3/4hp idler with no clutch. No belts squeal when it starts, it just spins right up.

    Disclaimer: I am the guy with the RPC designed by lakeside53. I can absolutely verify that it has been working for quite a number of years now. I can also tell you that when it comes to things electrical there is wisdom and there is wisdom. In other words, 10 people might chime in on a topic but only a much smaller number have any real deep knowledge of the subject. Lakeside53 is a person to pay attention to. Trust me.

    Here are some details from my build: to keep things as quiet as possible, my RPC sits on a rubber mat. Further, the idler motor has thick rubber "washers" it is mounted on. These are trivial touches, but quieter is easier to live with. Second, my RPC is in a small machinery room attached to the end of my shop which is under my house. Also in that room is my boiler and hot water heater. That room gets noticeably warmed when the RPC is running. In the winter, I take advantage of this by opening the machinery room door to let the heat in. In the summer, I use a small exhaust fan to blow the heat outdoors. Again, these are trivial matters but the end result is I don't have to heat my shop, and that's a big deal. (I'm in the Seattle area which has fairly temperate winters.)

    Another small touch that I continue to appreciate was adding 3 voltmeters showing the leg-to-leg voltages. Here's a not-so-great photo:



    It's very gratifying (and cool) to see all 3 meters reading very close to 240VAC. Means the balancing caps are working.

    If you are curious about the actual elements of my design electrically, lakeside53 already published the schematic above. I did make one change since then - I changed the output fuse block from 30A fuses to a 40A 3-pole breaker. I have several pushbutton stations around my shop. To turn on my RPC I just push the START button momentarily and that's it. The timer relay shuts off the pony motor after long enough for the idler to be up to speed (we chose 2 seconds). Dead easy. Reliable. Simple.

    metalmagpie
    Last edited by metalmagpie; 04-23-2021, 10:42 AM.

    Leave a comment:


  • Doozer
    replied
    Originally posted by nickel-city-fab View Post

    Actually I did just that. Imagine the power flow. When you cut the juice to the pony motor, the clutch will let go. Just like when you use a chain saw, you cut the throttle and it lets go. You can't back drive the engine with the chain. Tried that, and nope.
    Ride your mini-bike full throttle down a hill.
    Cut your ignition half way down the hill.
    The engine will keep spinning until the mini-bike
    slows down enough for the clutch to drop out.
    The bike going down the hill is adding energy
    back through the clutch and keeping the
    engine spinning, with cut off ignition.
    If you are going down a really long steep hill,
    the cut engine will keep spinning until you
    reach almost the bottom.

    -Doozer

    Leave a comment:


  • J Tiers
    replied
    The chain saw has much more friction than the pony is likely to. (and no power source fro the chain to reverse drive from) But see above.
    Last edited by J Tiers; 04-22-2021, 02:21 AM.

    Leave a comment:


  • nickel-city-fab
    replied
    Originally posted by Doozer View Post
    You're emoting.
    When people emote,
    they don't think clearly.
    Get calm and
    Imagine the power flow.

    -D
    Actually I did just that. Imagine the power flow. When you cut the juice to the pony motor, the clutch will let go. Just like when you use a chain saw, you cut the throttle and it lets go. You can't back drive the engine with the chain. Tried that, and nope.

    Leave a comment:


  • J Tiers
    replied
    Silly Doozer. Changing the subject.

    Think for a moment. You are going by theory, which is a valid approach, except that you have to get all the actions correct. Theoretically, if the speed were above the engagement speed, and it was a binary system, either "engaged" or "not engaged", it might drive in reverse. But it is "unstable".

    There are a couple types of clutch.

    One type "goes over center", in other words, it gets to a certain speed, then engages quickly. Ones where the shoe pivots like an old brake shoe, and is forced into the opposite surface by leverage. They are not so dependent on the speed to control the force once engaged, but are sensitive to power flow.

    Then there are ones that work only by a spring and "centrifugal force". Those have friction that is dependent on rpm. They are not as "positive" engaging, and slip until at a higher speed. That makes them very dependent on the difference between engagement speed and ultimate speed. The reverse side is that any slowing reduces the friction and the chance for reverse drive.

    The "brake shoe" type would potentially hold in, except that if there is force FROM the driven side, it breaks the force holding the shoe in contact, because that force is dependent on the opposite direction in which torque is applied. (same like the less effective "trailing" brake shoe). That force from the driven side would come when the idler gets power and accelerates up toward synchronous speed, while the pony loses power, and would require torque from the idler to speed it up against inertia. If there is some friction, like a belt drive, it should slow down OK. A lawnmower engine has plenty friction, and works fine.

    The "speed dependent force" type COULD reverse drive, but again the friction and inertia of the unpowered pony, combined with the sudden increase of speed by the idler as it gets powered, should break it loose. Once the pony slows at all, friction in the clutch begins to drop off, and eventually it should be uncoupled if there is reasonable friction in the pony system.

    Your real point (and mine) ought to be not that it is a slam dunk to work (or not), but that a proper system needs to be "designed". (we never did that, back then we were not aware of all the details, it just worked)

    The clutch should have a torque capability vs speed curve. If you WANTED it to back drive, you might be able to find a combination that WILL do it, by choosing a clutch which has a suitable torque curve, considering the engagement speed, and ultimate speed, with the pony friction and available torque.

    Conversely, there ought to be combinations that WILL NOT back drive in the system, because of the combination of engagement speed, ultimate speed, and torque curve vs friction from the drive side.

    Once you look at all that, it starts looking good to just let it start, then lever up the pony so that it throws the belt. Or, even simpler, just let the pony spin with the idler.
    Last edited by J Tiers; 04-21-2021, 10:20 PM.

    Leave a comment:


  • Tundra Twin Track
    replied
    Originally posted by The Metal Butcher View Post
    I'm still down for the clutch idea. I'd be highly interested if someone would be willing to test one before I drop $75 on a new bearing model. That's a lot to ask, but if anyone was curious themselves....

    At any rate, I'd appriciate it.
    Use a salvaged Chain saw clutch,machine the drum from a steel slug to fit your Idler shaft 1-5/8ā€ Iā€™m guessing.Take the flyweight hub and adapt to your pony motor two separate components,alignment will be critical.

    Leave a comment:


  • Doozer
    replied
    You're emoting.
    When people emote,
    they don't think clearly.
    Get calm and
    Imagine the power flow.

    -D

    Leave a comment:


  • The Metal Butcher
    replied
    I'm still down for the clutch idea. I'd be highly interested if someone would be willing to test one before I drop $75 on a new bearing model. That's a lot to ask, but if anyone was curious themselves....

    At any rate, I'd appriciate it.

    Leave a comment:


  • J Tiers
    replied
    Originally posted by Doozer View Post

    Once the centrifugal clutch is engaged, power flow is bi-directional.
    The shoes will stay engaged until the RPC motor is shut down.

    -D
    And, the earth is flat, there are thousands of mole children under Central Park, etc. šŸ˜

    Doozie, it's not that what you suggest is impossible in theory, it just does not happen with real clutches of the types under discussion

    Do I need to show a picture of one?

    Leave a comment:


  • Doozer
    replied
    Originally posted by nickel-city-fab View Post

    Well,. that's exactly what I think would happen -- the shoes on the type with a garter spring do not stick to the friction surface (the outer shell) by themselves. The only reason they fly out radially and grab, is because the hub is being spun faster than the outer shell. What happens when the hub is no longer being spun faster? The shoes retract. As JTiers says, when you cut the throttle it disengages while the driven part keeps on going. So if you used the generated leg on a relay to cut power to the pony motor, with the clutch hub attached, suddenly the pony motor would be spinning slower than the driven motor -- and the clutch would be disengaged. Lord knows I've picked enough of those clutches out of dead snow blowers. https://www.gokartsupply.com/clutches.htm
    Once the centrifugal clutch is engaged, power flow is bi-directional.
    The shoes will stay engaged until the RPC motor is shut down.

    -D

    Leave a comment:

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