How much power can these spur gears handle?

Gears like that are also used on many textile machines...
 
Superburban - In the 50HP range, you can likely achieve a better efficiency for generating. What limits your gasoline engine is low end torque in bringing a loaded generator up to speed. You probably don't put a load on it until you have it running at speed well. A large load can more easily stall out a gasoline or diesel engine. The small engines are also generally overrated.

Your point is good though - with 100 percent efficiency, 55 HP at 746 W/HP is around 37kW. Fortunately, he doesn't have to draw the whole 275 kW from the generator. I expect his tractor isn't going to net much more than 20kW though. after the speed conversion. The gear box is going to get very warm though. IMHO, belts are the way to go. Machinery Handbook or the Mechanical Engineering Handbook probably has the definitive answer.

Thanks. I was going to add something about efficiency at higher HPs, but while I was trying to think how to write it, I got a phone call, and had to leave, so I just hit Post.

Good point about running at less the full load. I should play around with some heavy loads on mine, to better understand how they handle loads.

Electricity is still one of those areas that I do not fully understand. Especially AC.

For Strantor, Keep in your plans a way to regulate the speed to keep the generator at the 1800 RPM's. My generators all have mechanical governors. If any one has some input as to how much leeway there can be with the AC frequency for various appliances, motors, electronics, ect, it could be a good addition to this thread.

I have a 5KW generator head I have been thinking about running off a PTO from my trucks transfercase. Speed regulation has been one of the issues I do not have a good idea on how handle.
 
Belts can be slipped to slowly engage, similar to a clutch. Its done that way on many riding mowers for the blades. You could use an idler pulley, pulled to tension the drive belt, and give the slip needed.

Is that 275KW right? My 3KW generator has a 6 HP engine, my 1.5KW, has a 3HP. Going by that same ratio, you are looking at needing 550 HP.
Yes 275kW is not a typo, and 550hp sounds about right. The Caterpillar diesel genset that this generator was born to be married to, has about the same dimensions as a full size pickup and weighs several times more. 550HP is how much grunt you need to get 275kW out if it. But you can still use it at less than its rated electric output with a smaller engine. I'll be using it behind my tractor as a whole home generator but If I had 550HP worth of tractor, it could be a whole-city-block generator.
 
But Can your tractor move it? Would love to see some pics.

Have you considered a dedicated power plant? I'm thinking something like buy an old beat up pickup, strip the cab, Keep the engine, trans,and radiator. Make the frame into a small trailer, and mount the gen head to the engine. A manual trans, would give you the clutch, and a way to hook up the two (driveshaft).
 
You need to calculate your mass moment of inertia, it might require all the hp of your tractor just to rotate the thing.
 
But Can your tractor move it? Would love to see some pics.

Have you considered a dedicated power plant? I'm thinking something like buy an old beat up pickup, strip the cab, Keep the engine, trans,and radiator. Make the frame into a small trailer, and mount the gen head to the engine. A manual trans, would give you the clutch, and a way to hook up the two (driveshaft).

Pics attached.

Yes, assuming you mean physically move it around, my tractor can move it . Just barely though, with the front end loader. These weigh 1,800lbs and they're on the ragged edge of what my front end loader will lift. With the generator head all the way back against the headache rack, I can lift it. If I move it just 2" more forward on the forks, I can no longer lift it. I will mount it on a trailer and then lifting it will no longer be a consideration.

As you see in the pics, I have two of these. I also have a wrecked 1997 Jeep XJ that should theoretically still run. The plan is to build the PTO generator running first, and then get the jeep running. Once the jeep runs (it will never drive on the road again) I will pursue installation of the 2nd generator head inside the passenger compartment of the jeep. The "Jeeperator" project will consist of ripping out the back seats and cutting a hole in the floor board, uncouple the driveshaft from the rear axle and bring it up through the new hole and couple to the generator input shaft. I'll pour a little concrete pad on the side of the house by the main breaker panel and park it there with the good side facing out so that you can't see that it's wrecked, and when the hurricane comes and knocks out my power, I'll just go out there and get in it, start it up and put it in gear, hold the gas pedal down until the speedo reads about 55mph and set the cruise control. According to my math, 55mph should give me 60hz output. Hopefully the cruise control circuit is responsive enough to keep the output reasonably level or else I'll have to make my own PID controller for it.

I know I can make the PTO genny work, relatively easily. That's why it's up to bat first. The jeeperator is a bag of question marks and therefore not on the top of the list. If the jeeperator eventually works then I'll probably try to sell the PTO generator (as if anyone but me would be interested in such a wacky thing) or keep it around as a double redundant backup.

You need to calculate your mass moment of inertia, it might require all the hp of your tractor just to rotate the thing.
You're not the first person to say this. I've discussed this project on tractorbynet.com as well as Facebook and several people have mentioned it. Enough people to make me doubt my own understanding of the physics behind it, but not enough to make me stop going forward. I still think I'm correct but if someone can explain why I'm not, I'm all ears. According to me, the moment of inertia is only of concern when getting it up to speed. Once at speed (assuming no electrical devices are connected and drawing power) the only resistance that it will pose to the tractor (or jeep or other power source) is that which is required to energize the windings (740W, almost squarely 1HP), plus air resistance, plus resistance of the bearings which is negligible. I'm conservatively counting on 5HP max parasitic load with no devices connected to it drawing power. It will probably be less than that. I should theoretically be able to spin this thing up to operating speed with a weed eater motor. It's a brushless design and I can spin it freely by hand (not up to 1800rpm unfortunately); it takes some strain to get it up to [maximum hand RPM] but once there, it does NOT want to stop. It will spin for a minute or more before crawling to a stop. Once at 1800RPM , and I start adding electrical loads to it, those loads should be presented to the tractor just as they would be with a smaller generator head. If I connect a 5HP compressor to it, then it should demand about 5hp additional from the tractor (plus a fraction, it's about 95% efficient).

I'm having a hard time picturing 55HP (picturing a VW bug engine) doing much for this (from a google search, I do not know if this is the same one Strantor has). Puts my generator project to shame.

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https://www.ebay.com/itm/CATERPILLAR-5N88-275KW-GENERATOR-END-/283335735899?oid=283301262382

Yes, that's exactly the beast. In fact, that's the guy I bought my generator heads from. You'll see the rest of his inventory in my attached pictures. He is an asset liquidator who recently purchased a Caterpillar repair facility gone out of business. He's selling them as used but he doesn't know what he has. These are refurbished by the company he acquired. At least the two that I got were. I brought my tools with me, took some panels off and looked under skirts. Some of them are used and failed my merger checks; shorted stators. I hand picked which ones I wanted and I gave $1400 for the pair of them. They're worth at least $10k in refurbished condition. I was getting ready to spend that $1400 on a single 30kW ST generator head on Ebay that I've had my eye on for the past year. Decided to briefly check if there was a better local deal before I pulled the trigger, and found these.


Some details about the project: the generator heads have only one bearing, in the far end. The other end is meant to be bolted directly to (via flex plate) and supported by the Caterpillar engine flywheel/crankshaft. So I had to come up with a way to support the flaccid end. I drew a few different designs but all of them were beyond my machining capacity due to the size. So I figured out that the bolt pattern on the generator is an SAE standard bolt pattern (SAE#0). From there I started looking up engines with a bell housing that was a match. Some 18-wheelers are using this standard as well. I found a local guy on craigslist selling an engine bell housing from a Detroit Diesel 12.7L engine and brought that home. It fit. It has a ~5" circle in the center concentric with the outer bell housing machined radius. Perfect. I machined an adapter to keep a 2" flange bearing centered in it. Then I had to figure out how to get the rotor shaft to extend out past the bell housing. I cut the 2"x3" cylindrical tit off the end of the rotor (and nearly lost a finger in the process) and machined/welded this wacky shaft adapter to come out about a foot. That part is back in the lathe right now to be cut down and turned to the correct size to fit whatever gear/pulley/sprocket I end up using. It's shown in the pictures being haphazardly held in place by some bolts. That's not the plan. There will be a bolt flange welded to it as the last step, as once I weld it, it will no longer fit in my lathe.

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Now you are talking my kind of project. Just hope yours does not take the years mine does.

Sounds like you have all the details worked out. Except, what are you going to do with 550KW of power?
 
Now you are talking my kind of project. Just hope yours does not take the years mine does.

Sounds like you have all the details worked out. Except, what are you going to do with 550KW of power?
It's taking quite a while. I hope to have the PTO generator done before a year of dust settles on it, but the jeeperator is realistically part of my 5 year plan. I'm far from having all the details worked out. I don't even know how I'm going to step the speed up. I gave V-belts a good hard look again last night, and that's probably the way I should go. When I looked into it before, I was looking at pulley combinations that I could get from SuplusCenter, where the larger pulley was 18.75" (the biggest they have), which meant I would need several pulleys and belts in parallel. I looked on Ebay and found huge (used) pulleys in single and double belt configurations which would increase contact area and decrease belt stress, allowing me to use fewer belts. It still won't be cheap, but it will be closer to achievable.

I won't have 550kW of power. Or 275kW. Not even close. I should realistically be able to get maybe 20kW out of it (which is pretty close to all I need), coupled to my tractor. Coupled to the jeep, maybe 100kW in short bursts, but not sustained without overheating. If I wanted to get the rated 275kW from it, I would need to go buy the Caterpillar skid engine that goes with the generator head. The 30kW ST generator head that I was looking at before, would have served my purposes just fine. I have no use for 275kW of power. The benefits (as I see it) of using this generator head over the 30kW Ebay ST head are as follows:

1. The Cat head is Made in America. The Ebay head is made in China. I expect the American one to be more reliable.
2. I'll only ever be using it at (max) 1/10th of its rated capacity. It should last forever since it will never have to break a sweat.
3. Two for the price of one. If being made in America and being treated like a baby don't lend to longevity like I hope, I have a whole 'nother generator head to pull parts from. With any luck I'll never have to buy parts for this thing.
4. The huge rotating inertia of the rotor, while a burden to get started, once at speed should act as an extremely heavy flywheel to power through instant high power surges (like starting the home central A/C) without any flicker in the lights and irritation of electronic gadgets.
5. It's a 12-wire, 3phase generator. It can be configured for 3 phase or single phase output at 120V, 240V, or 480V output. The 30kW Ebay unit is just 120V/240V single phase. I may actually need that 3ph 480V capability for my day job. I build control panels for industrial installations. Right now I power them from a [RPC + transformer] but it pulls a LOT of juice from my residential service and makes my neighbors lights flicker. And I've never even done any real high power testing. If, for example, I ever need to do a FAT with a customer witness, this would be a much better way to go about it.
6. It's big and yellow and Caterpillar. It's impressive (to me, anyway). Not quite on the level of having a Corvette in your driveway, at least not in normal people's way of thinking. But in my nerdy way of thinking, it's super cool and I know that nobody else within a 50mi radius has anything like it.


What's this generator project of yours? Is there a forum thread about it? I'd like to see/hear some details.
 
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Wasting a bit more time looking at belts, I waffled back to gears. Using the calculator on rushgears.com, it seems that a 5dp 12T gear ($39) mated to a 5dp 40T gear ($186) will give me the speed change that I want, without causing any surface speed or torque concerns, and will be more efficient than a friction-inducing V-belt setup.
spurgear1.PNGspurgear2.PNG

But then I lose my clutching action. But there's an app for that. Apparently tractor people have already identified the need for such a thing, and designed an adjustable PTO slip clutch ($130). So, $355 total, not including bearings and intermediate shafting which I already have, and that's less than just one of the big multi-groove v-belt pulleys I would need if using belts. It will be simpler to build, I think, as there won't be any belt tensioning adjustments needed.
 
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