Has anyone ever made a reduction gearbox?

RC99 · Mar 12, 2019

I need to make an inline reduction gearbox of close to 1.5:1 ratio to slow the output of a small 27hp diesel motor to 1500rpm to run a generator. No more then 50ft lb's torque on the input.

Are these incredibly complex things to build or just relatively basic so long as you have good common sense.

steve-l · Mar 12, 2019

RC99 said:
I need to make an inline reduction gearbox of close to 1.5:1 ratio to slow the output of a small 27hp diesel motor to 1500rpm to run a generator. No more then 50ft lb's torque on the input.

Are these incredibly complex things to build or just relatively basic so long as you have good common sense.

I don't think it would be overly difficult, but I can't believe it makes any economic sense or is in the least bit practical. It appears you have a 4 pole alternator and want to make 50 Hz power. You are far better off selling your 4 pole and buying a 2 pole alternator, then get the correct engine governor and be done with the problem.

Peter from Holland · Mar 12, 2019

Why not use a V-belt transmission ?

Peter

Milland · Mar 12, 2019

I've seen simple toothed-belt with taper roller bearings supported shafts used for stepping down engine output, and that unit lasted for years. But I'm surprised that your engine has a base RPM of 7500, that's awfully high for a diesel.

wheels17 · Mar 12, 2019

Old guy I knew made a 2:1 out of the sprockets and chain from an car engine. I don't know if that is too far off for you. A lot less critical than gears. Autozone sells a silent chain set for $22.99. https://www.autozone.com/internal-engine/timing-set/duralast-timing-set/752881_690132_0

A little research may find mixed automotive parts that would get you closer to 1.5 to 1.

MattiJ · Mar 12, 2019

Milland said:
I've seen simple toothed-belt with taper roller bearings supported shafts used for stepping down engine output, and that unit lasted for years. But I'm surprised that your engine has a base RPM of 7500, that's awfully high for a diesel.

1½ to 1

I'd also take a hard look on belt drive possibility, lot more forgiving to build than inline gearbox.

Milland · Mar 12, 2019

MattiJ said:
1½ to 1

I'd also take a hard look on belt drive possibility, lot more forgiving to build than inline gearbox.

Too early in the morning for me, I misread it as 5:1. D'Oh!

Dumpster_diving · Mar 12, 2019

I'm going to second the belt drive simplicity. There are pto driven chippers that achieve a similar result with a jack-shaft pulley arrangement (3 v belts to handle the load).

Cole2534 · Mar 12, 2019

Belt drive could even still be inline, just require a mid-shaft.

DDoug · Mar 12, 2019

The homebuilt aircraft crowd has several different manufs that do just this.

IIRC rotax probably has what you want.
Rotax gear boxes, Rotax reduction drives, Rotax A gear box, Rotax B gear box, Rotax C drive, Rotax E drive.
Recreational Power Engineering - Hirth Engines - Tiffin, Ohio - Factory Authorized US Distributor

Zahnrad Kopf · Mar 12, 2019

Make them all the time. Planetaries, even. For your needs, you'd do well to heed the advice given and look at pulleys, belts, and jack shafts. Easy-peasy.

Dumpster_diving · Mar 12, 2019

One cautionary note (not to dissuade from going the pulley route) but just to consider.

A gearbox will usually pretty much lock in alignment. A simple and cheap pulley/jack-shaft arrangement is often based on pillow-blocks. Those arrangements can be sensitive to alignment issues. I snapped a 1 1/2" chipper jack shaft after carelessly keeping the chipper engaged while I lifted the implement. Resulted in a minor misalignment of the input shaft which wobbled the jackshaft without my realizing it. The fatigue from running the misaligned 1 1/2" shaft even for just a minute or two snapped it like a toothpick.

Not saying that misalignment couldn't damage a gearbox...and not saying it wasn't 100% user error on my part...just observing pillow blocks don't take much torque to misalign.

Ray Behner · Mar 12, 2019

I agree with Zanhrad. Here;s a simple reduction I made for my snow blower. Worked fine, just took forever. Poke the pic for more.

PDW · Mar 12, 2019

RC99 said:
I need to make an inline reduction gearbox of close to 1.5:1 ratio to slow the output of a small 27hp diesel motor to 1500rpm to run a generator. No more then 50ft lb's torque on the input.

Are these incredibly complex things to build or just relatively basic so long as you have good common sense.

I've got a 2 pole 7.5kW generator head I'd swap for a 4 pole..... freight/distance probably a deal killer though. Or I could do you a good deal on a Lister 1500/1800 rpm diesel. Kind of planning the same thing as you but the reverse - I need to get the generator head up to 3000 rpm.

Email me if you're interested. We might be able to work something out on freight as I'm driving north in another month or 2.

PDW

johnoder · Mar 12, 2019

Here are two "coaxial" or inline reducers I used on this head stock over 30 years back. So you can certainly BUY such things

adama · Mar 12, 2019

Honestly the hardest bit is making it oil tight, the gears are best bought of the shelf the rest is a couple of bearing fits, Holding shaft centers to typical good machining tolerances works just fine.

Belt drive and out of line is far easier, but most small alternators are not setup for belt drive side loads.

Guest · Mar 12, 2019

adama said:
Belt drive and out of line is far easier, but most small alternators are not setup for belt drive side loads.

You would be surprised at some of the loads we put on beefed up automobile alternators and never smoked any bearings. We are talking spinning 200+ amp alternators at over 8,000 RPM with nothing but the stock cheap Chinese bearings in them that at the time in volume cost a measly $1.50 each. Due to the excessive drag created the belt had to be run on the tight side.

RC99 · Mar 13, 2019

Thanks, I did consider belt drive but wanted to get away from that. I could buy a 2 pole but a suitable one is $2000. Compared to the current $0 in the current one, which if sold would only be worth scrap as who would believe you it worked. It is a good alternator 15kVa continuous @ 240V 0.8 pa.

Still keeping my options open.

PDW · Mar 13, 2019

RC99 said:
Thanks, I did consider belt drive but wanted to get away from that. I could buy a 2 pole but a suitable one is $2000. Compared to the current $0 in the current one, which if sold would only be worth scrap as who would believe you it worked. It is a good alternator 15kVa continuous @ 240V 0.8 pa.

Still keeping my options open.

My plan is/was to use belts but I've got an alternator that has bearings front & back not using the crankshaft to provide the front bearing. Plus I have 2 spare air cooled diesel engines.

An inline gearbox would be a lot neater though.

PDW

adama · Mar 13, 2019

Dualkit said:
You would be surprised at some of the loads we put on beefed up automobile alternators and never smoked any bearings. We are talking spinning 200+ amp alternators at over 8,000 RPM with nothing but the stock cheap Chinese bearings in them that at the time in volume cost a measly $1.50 each. Due to the excessive drag created the belt had to be run on the tight side.

Yes car alternators have bearings both ends, lots of generator mounted "power aka mains voltage" alternators only have a bearing the far end! its how they effectively get around the whole shaft alignment issue. Equally they tend to bolt straight onto the fly wheel face, so lots don't even really have a shaft more some kinda coupling flange.

200 amps at 12v is only what 2.4Kw? Aka 3hp ish? Were looking at 15kw over 6 times more transmitted power here and far more than a single V belt will transmit.

Has anyone ever made a reduction gearbox?

Diamond

Titanium

Diamond

Diamond

Stainless

Titanium

Diamond

Cast Iron

Diamond

Diamond

Diamond

Cast Iron

Diamond

Diamond

Diamond

Attachments

Diamond

Guest

Guest

Diamond

Diamond

Diamond

Similar threads