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How much power can these spur gears handle?

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strantor

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I pulled these out of a scrap bin at a place I used to work 10 years ago. They are brand new. I don't know what their intended purpose was. They have 7/8" keyed shaft and are 7/8" thick. All of them Stamped MP02877, I get no results googling that. No brand stamped on them. They come in teeth of 39, 37, 33, 31, and 25. I believe They're steel, not cast, as I get a high pitched "ping" when I tap them together.

I'm considering using them in my tractor PTO generator project. Ultimately (extra long term goal, years down the road when I upgrade my tractor to 55hp) I will need to turn 540ft×lbs @ 540rpm into 160ft×lbs @ 1800rpm. For now the max PTO HP my tractor can put out is 32hp, so (shorter, this year) long term goal is turning 310ft×lbs @ 540rpm into 94 ft×lbs @ 1800 rpm. But before I do any of that, I just need to test my generator, make sure it puts out the proper voltage if I can manage to get it up to 1800rpm. I SWAG that will take 5hp max, so say 50 ft×lbs @ 540 rpm into 15ft×lbs @ 1800 rpm.

Will these gears help me accomplish any of those goals? Or are they too weak to even handle 5hp? I just want to know if I'm wasting my time before I go putting a hurt on my brain calculating if the RPM change will work out given the gears I have and the ratios I can create.

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strantor

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According to that calculator:
39t @ 1800rpm = 17.5hp
39t @ 540rpm = 11hp
25t @ 1800rpm = 14hp
25t @ 540rpm = 7.87hp
So I could use these for testing, to get it up to speed. However, the tooth counts are not in my favor. I could only use 4 of the 5 gears for speed change, and the max ratio I could achieve would be 1:1.862. The math was way easier than I thought it would be, and took less time than asking this question.
 

john.k

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Check the gears for hardness.....this will give a good clue to suitability...........they should not scratch with a hacksaw teeth across the pressure face.....if the saw cuts easily,they are no good for what you want.............In any case ,the setup will depend on the accuracy of the machining you do to the case.............If it were me,I would use an old truck gearbox thats already suitable for ratio,and remove the unwanted gears...........You should also note,there is going to be a big power loss in gearup and down ,so your setup wont be fuel efficient,but ok for ocassional use.
 

benmychree

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That job should be done with multiple vee belts, not spur gears. I suspect that those gears were intended for change gears on a lathe..
 

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So now that the gears are put to bed, what solution would you gents consider, for stepping the speed up by a factor of 3.333? I would prefer to skip the intermediate steps and design around the 55hp goal as I'm feeling pretty good about this generator and I want to believe it will work.

The rotor has a ton of inertia (it's actually a 275kW Caterpillar generator head meant to power an oil rig) and my tractor has an electric clutch that's either ON or OFF. I can't feather the PTO clutch to get the rotor up to speed. I have a bad feeling about engaging the PTO while connected to this thing as I suspect it will stall the engine or destroy the PTO clutch/drivetrain. For that reason I like the solution of V-belts because I could engage the PTO with the belts slack, and then slowly increase belt tension as a sort of secondary clutch. The problem with belts, is that at these power levels (according to the formulae in belt MFG whitepapers) I would need a combination of large pulleys (expensive) and several pulleys/belts in parallel (expensive × n).

It's the same story for chains, but actually even worse, because achieving that ratio with a single set of sprockets would require me to derate the setup to the point of uselessness due to the tiny sprocket. So I would need multiple stages of multiple sprockets with multiple chains (again, according to whitepapers - not sure about real life).

The option I like best, is a manual automotive transmission with a manual clutch, but that would be heck of an endeavor to build.

Any other thoughts?
 

strantor

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Another option on the table is toothed synchronous belts (timing belts) but I can't for the life of me find any reference for how much power these things can transfer. I know it's "more than a regular v-belt" and that's it. If anyone has a good reference for those things, please pass it along. So far all I'm getting from the MFG websites is "schedule an appoint with one of our applications Engineers to determine the requirements of your OEM design. "

EDIT:
oh, and multiple groove flat belts (automotive serpentine belts)... same story there. Any reference appreciated.
 

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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.
 

tcarrington

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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.
 

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Until I saw that the gen was 275kw, I was going to suggest a hydraulic drive setup. Oh well back to thinking!
 

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Gears like that are also used on many textile machines...
 

Superburban

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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.
 

strantor

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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.
 

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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).
 

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You need to calculate your mass moment of inertia, it might require all the hp of your tractor just to rotate the thing.
 

strantor

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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.

View attachment 284908

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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Superburban

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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?
 

strantor

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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?
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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strantor

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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.
 

Superburban

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You are right, I keep forgetting you are not going for full potential.

My current project is this little Honda 1600. In got it free planing on parting it out. Looks like it took a dive off the back of a truck. It would turn so far, and stop. I thought it threw a rod, and bet the PO thought the same thing. When I opened it up, it had dropped a valve. I'm thinking that when it got dropped, the valve spring compressed enough to let the retainer pop off. The valve was the only casualty. Cylinder, piston, and all insides look great. I got a set of valves, also picked up a new carb, ignition parts, rewind starter, and some other small stuff, for less then $20, Just waiting on the gasket set, then I will hope I can remember how it all fits back together.


100_0749.JPG

The future project, is this 5kw head. I have a PTO that will mount to the NP435 in my pickup. I planning on using a half shaft off a minivan, as the drive shaft. Then likely a set of pulleys to get the right speed (Still have not calculated the output speed of the PTO). Right now, the plans are to have it run at the 3600 RPM, while the engine is at idle, and have a switch mounted to the gas pedal, or a speed sensor, to shut down the engine if the RPMs get above the idle, or 3600 at the gen head.

100_0744.JPG100_0745.JPG

I also have 2 military generators (3KW, and a 1.5KW), that I would like to get running, just need some more roundtuits.
 

john.k

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I would think your cheapest option is to buy an old truck motor and power the genset direct coupled.......dunno about US,but an old Cat 3406 can be bought for scrap price,same with GM s...around $500
 

strantor

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I would think your cheapest option is to buy an old truck motor and power the genset direct coupled.......dunno about US,but an old Cat 3406 can be bought for scrap price,same with GM s...around $500
Cat engine around here can't be had for any price close to reasonable. And even if someone gifted one to me, I couldn't afford the rebuild parts. But a GM 5.7L, yeah I could get that for <$500 for sure. Problem is, 1800rpm is low for a gasser. They have no power down there. Searching online for a dyno graph of a stock 350, If you can even find an example that goes that low, you'll see they have less than 50hp down there, about the same as my tractor which I already have and don't even need to spend $500 for. If I wanted to use a GM 350, I'd need* to run it at a decent rpm and gear it down. And then I'd be right back where I am now.


*I suppose I wouldn't actually need to. I could just go ahead and direct couple, and accept the low power output since it's probably sufficient anyway, but then I'd still be paying for an engine and all that goes along with it, which might cost as much or more than the gearing I need to make it work with the tractor. It deserves more thought and investigation. Any idea what kind of fuel economy an old 350 would have, being run so far away from peak efficiency?
 

Superburban

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Kinda out of the box thinking, Get a gasser with a manual tranny. If you do not need much power, you run it in 4th gear (or which ever has the 1 to 1 output for the tranny), and run the engine at the 1800 RPM. Need more power, and shift the tranny to third (Usually close to a 1, something to 1 ratio), and run the engine at the right speed to get the 1800 output RPM, like 2600 or so. Gobs of power, shift into 2nd, which is usually 2.whatever to, and run the engine at the approx 3800 or so RPMs.
 

NortonDommi

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I was interested in your comment about the friction with belts. Belts are a very efficient means of power transmission and quiet and don't need lubrication.
The .zip file has a demo calculator in it. The only stuff dedicated to synchronous drives is in hard copy sorry but there is a little bit in the Gates catalogue. The Opti-belt one has some calculations on page 90.
Synchronous drives,(timing belts), are readily available up to 150 kW,(think motorcycle), and more with special order, meaning not in the back room of your local dealer. Not sure of the max ratings on Polly-V belt as larger power ratings usually go for linked back V.
Most PTO's regulation is pretty good within working range on modern tractors so a clutched,plate or cone, gearbox is definitely a go.
 

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strantor

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Kinda out of the box thinking, Get a gasser with a manual tranny. If you do not need much power, you run it in 4th gear (or which ever has the 1 to 1 output for the tranny), and run the engine at the 1800 RPM. Need more power, and shift the tranny to third (Usually close to a 1, something to 1 ratio), and run the engine at the right speed to get the 1800 output RPM, like 2600 or so. Gobs of power, shift into 2nd, which is usually 2.whatever to, and run the engine at the approx 3800 or so RPMs.
That's basically the idea behind the jeeperator except it's automatic so if someone turns on the dryer while it's in 4th gear and sipping fuel, it will downshift automatically and I can stay in bed. Or at least that's the way I see it working. I can't find evidence of anyone else having made a generator work with an automatic transmission, so that probably means that it I doesn't. I'm sure people have tried it, but how many people run to YouTube to document their failures?
 

strantor

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I was interested in your comment about the friction with belts. Belts are a very efficient means of power transmission and quiet and don't need lubrication.
The .zip file has a demo calculator in it. The only stuff dedicated to synchronous drives is in hard copy sorry but there is a little bit in the Gates catalogue. The Opti-belt one has some calculations on page 90.
Synchronous drives,(timing belts), are readily available up to 150 kW,(think motorcycle), and more with special order, meaning not in the back room of your local dealer. Not sure of the max ratings on Polly-V belt as larger power ratings usually go for linked back V.
Most PTO's regulation is pretty good within working range on modern tractors so a clutched,plate or cone, gearbox is definitely a go.
You're right. I remember being wrong about the efficiency of v-belts the first time I went through this. I forgot that lesson. It does not seem intuitive to me that they are efficient but they are.
 

strantor

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You are right, I keep forgetting you are not going for full potential.

My current project is this little Honda 1600. In got it free planing on parting it out. Looks like it took a dive off the back of a truck. It would turn so far, and stop. I thought it threw a rod, and bet the PO thought the same thing. When I opened it up, it had dropped a valve. I'm thinking that when it got dropped, the valve spring compressed enough to let the retainer pop off. The valve was the only casualty. Cylinder, piston, and all insides look great. I got a set of valves, also picked up a new carb, ignition parts, rewind starter, and some other small stuff, for less then $20, Just waiting on the gasket set, then I will hope I can remember how it all fits back together.


View attachment 284980

The future project, is this 5kw head. I have a PTO that will mount to the NP435 in my pickup. I planning on using a half shaft off a minivan, as the drive shaft. Then likely a set of pulleys to get the right speed (Still have not calculated the output speed of the PTO). Right now, the plans are to have it run at the 3600 RPM, while the engine is at idle, and have a switch mounted to the gas pedal, or a speed sensor, to shut down the engine if the RPMs get above the idle, or 3600 at the gen head.

View attachment 284981View attachment 284982

I also have 2 military generators (3KW, and a 1.5KW), that I would like to get running, just need some more roundtuits.
What kind of truck do you have, which has a PTO? I continue to window shop (as I have for the past 2 years) for a new truck, and was particularly interested by Ram's optional offering of a PTO. I did not see that available on any of the other trucks. I can think of all kind of cool stuff to do with a PTO on a truck. I googled NP435 and saw that it went out of style in 1997 so I assume it's an older model pickup?
 

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Its a 90 Dodge W250. Its one of the newer trucks in my fleet. Most are 77 Dodges. I also have a PTO that will mount to a NP203, from the 77. It will power a PTO driven Ramsey winch.

The NV4500 which basically replaced the NP435, has PTO openings, but good luck finding a PTO that will fit. I do not know how long or if it is still used. I just like trucks that do not cost a fortune to buy, and keep running.

Intriguing idea with the auto tranny. I've been thinking it through all day.
 

pdentrem

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Jan 28, 2011
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Looking at the use of an automatic tranny, I would think an electronic cruise control could control the engine rpm under variable load. I think that having the speed sensor on the driveshaft is the way to go. Some new cars are using the ABS sensors to tell the PCM what is happening. The PCM then controls the engine. Problem could be finding a cruise control kit to do so!
 
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