Author Topic: Treadmill motor with 6.5 hp gas engine  (Read 3278 times)

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Davers

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Treadmill motor with 6.5 hp gas engine
« on: August 03, 2016, 08:23:59 AM »
I currently have a 90 volt d.c. pm treadmill motor running
off of a 6.5 hp motor, idle speed produces 48 volts.
https://www.youtube.com/watch?v=jqe-rZfjFrk&

I plan on using 4 ohm (100) watt resistors in parallel to
reduce the voltage to a desirable amount for a charge controller.

Any thoughts on using resistors? if my math is correct 4 ohms should work well.
The resistors are encased in a aluminum heat sink. I have five 100 watters.

joestue

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Re: Treadmill motor with 6.5 hp gas engine
« Reply #1 on: August 03, 2016, 01:12:38 PM »
Why not just reduce the rpm?

hiker

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Re: Treadmill motor with 6.5 hp gas engine
« Reply #2 on: August 03, 2016, 01:18:48 PM »
Try a car or truck alt..more output than that treadmill motor..get one with a built in regulator..easy build...
WILD in ALASKA

Davers

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Re: Treadmill motor with 6.5 hp gas engine
« Reply #3 on: August 03, 2016, 06:32:15 PM »
Try a car or truck alt..more output than that treadmill motor..get one with a built in regulator..easy build...

That is reduced to the lowest idle point it will go without stalling.

Ungrounded Lightning Rod

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Re: Treadmill motor with 6.5 hp gas engine
« Reply #4 on: August 03, 2016, 07:56:40 PM »
Try a car or truck alt..more output than that treadmill motor..get one with a built in regulator..easy build...

That is reduced to the lowest idle point it will go without stalling.

You're already using a v-belt drive.  Use different sized pulleys to adjust the speed.  That way the design speeds of the genny and the motor can be chosen independently.

Davers

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Re: Treadmill motor with 6.5 hp gas engine
« Reply #5 on: August 03, 2016, 09:47:50 PM »
Thanks,
Great idea. Right now its 1:1 gear ratio.

Plus a larger pulley on the generator will allow for more torque.
Less stall-out if there is a heavy load on the generator side.


george65

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Re: Treadmill motor with 6.5 hp gas engine
« Reply #6 on: August 08, 2016, 06:39:26 AM »

With the size of the treadmill motor and the size of the petrol engine, You won't need to gear down the treadmill motor for extra torque, the 6.5 is overkill already.

Are you wanting to get the best power or just some power?  If you are looking to get more power for faster battery chargine or heavier loads, You would do better with a car or truck alternator.
If you use a leece Nevil  with an EXTERNAL controller, You will get efficency as high as any other generator.

You can also control the voltage from 12 Up to 48.

XeonPony

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Re: Treadmill motor with 6.5 hp gas engine
« Reply #7 on: September 09, 2016, 08:39:10 AM »
Tread motors are not use full at all for this application, all the current going through the brushes eats them fast.

Get a good heavy alternator from a truck as all have said, gear it up with the pulies as you want it to spin at about 2.5Krpm

this will produce far higher amperage and better power.
Ignorance is not bliss, You may not know there is a semie behind you but you'll still be a hood ornimant!

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joestue

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Re: Treadmill motor with 6.5 hp gas engine
« Reply #8 on: September 09, 2016, 12:24:19 PM »
Tread motors are not use full at all for this application, all the current going through the brushes eats them fast.

then fix the problem(s)

read this. http://industrialelectricalco.com/wp-content/uploads/2014/01/DC-Motor-Brush-Life-White-Paper.pdf

hiker

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Re: Treadmill motor with 6.5 hp gas engine
« Reply #9 on: September 10, 2016, 11:10:10 AM »
Don't really need that much hp. Even a 3 hp lawnmower engine works great.just put a larger pully on the alt. than what's on the engine..or lower the field strength...don't really need a lot of rpm as well ..just to charge batts..some kind of clucth .makes it easyer to start..Manuel or auto....
WILD in ALASKA

XeonPony

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Re: Treadmill motor with 6.5 hp gas engine
« Reply #10 on: September 10, 2016, 11:15:02 AM »
Tread motors are not use full at all for this application, all the current going through the brushes eats them fast.

then fix the problem(s)

read this. http://industrialelectricalco.com/wp-content/uploads/2014/01/DC-Motor-Brush-Life-White-Paper.pdf

lol I did, I just don't use systems that rely on brushes ;)
Ignorance is not bliss, You may not know there is a semie behind you but you'll still be a hood ornimant!

Nothing fails like prayer, Two hands clasped in work will achieve more in a minute then a billion will in a melenia in prayer. In other words go out and do some real good by helping!

Ungrounded Lightning Rod

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Re: Treadmill motor with 6.5 hp gas engine
« Reply #11 on: September 26, 2016, 05:56:44 PM »
Don't really need that much hp. Even a 3 hp lawnmower engine works great.

1 HP = 745.69987 Watts (almost exactly 3/4 of a KILOwatt).  So even with a moderately inefficient generator, a 3 horse engine idling (rather than in its peak horsepower output) can easily give you a couple hundred Watts to charge your batteries or whatever.

An alternator already has exactly the regulator you need for charging your battery properly from a broad range of input RPM.  Just belt it on with a pulley size that ends up with it spinning in its normal operating range, wire it properly to pull a bit of excitation off the battery, and only run the engine with a battery connected to the alternator (or install an overvoltage protector - a varistor that hangs across the alternator output to keep it from committing suicide if there's no battery attached) and you should be fine.

(If it stalls your engine you might need to adjust your pulleys to get it to only charge when you've revved it up a tad, but that shouldn't be an issue with a 6.5HP engine.)

george65

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Re: Treadmill motor with 6.5 hp gas engine
« Reply #12 on: September 26, 2016, 08:35:57 PM »
Quote
and only run the engine with a battery connected to the alternator (or install an overvoltage protector - a varistor that hangs across the alternator output to keep it from committing suicide if there's no battery attached) and you should be fine.

Just for a bit of info......

I have access to basicaly an endless supply of Mitsubishi internal (2) fan alternators from Subaru's and have played with them a lot. These alts are on a lot of different makes and models with the main difference being the mounting bracketry/ flanges.

I have tested this " Run without a battery " theory for blowing them up for many hours and have NOT been successful with these units.
Some of them are the 2 wire units and some the 3 for the car computer turning them on and off but they are all basically the same and NONE of them have failed.

I have run them energised with no load and I have run them energised Overloaded and they don't fail ( or crash the windings) no matter what state they are in.  I guess the best way to test these things is try to make it happen rather than avoid it and If haven't been able to create the fault so far, I would guarantee that it is not a problem on these alts.
I think a lot of these fears and warnings linger for many years and become out of date. The alts I have tested are up to 20 yrs old and done several hundred thou KM on the cars before I got to them.  It is rare to sell these as replacements, hence why I can get so many.  While I have mainly tested the Mitsi alts, I have run the older Bosch external fan type quite a bit in the same way and haven't had a failure with those in 12 or 24V versions either.

I have also run these alts flat out for hours trying to see how much heat I can get in them and they can get hot enough not to be able to touch yet still put out over rating amps and do so seemingly indefinitely.  The twin fan design is great because one fan cools the windings and the other the electronics/ regulation at the back. I think this is a key to their robustness and Longevity.

I Suppose compared to the under bonnet temps they would experience, any stationary engine use where they are in free, cold air is going to be a doddle for them. The Concealed Twin fan design appears very robust and so far, I have been unable to break one despite all reasonable efforts.
I have seen plenty reverse connected on vehicles and blow main fuses and computers but never take out an alt. 
The other thing I have tested a couple of times is trying to explode them through High RPM.  I have geared them up to almost 15,000 rpm at which point the make a noise like a turbine  engine but they never looked like letting go.

The alts I have tested are rated at 80A and will exceed that output on every one I have metered.  On a 12V system, this is slightly better than 1Kw output and these alts deliver very well at low speeds as well.

I'm not sure of their efficiency in standard form.  I would guess like most claw pole alts, the design of the alternator itself is good, it's the same design they use on commercial alts and there are only a couple of percent efficiency differences.  The real variation lies in the control circuitry.
Car alts live in some pretty horrific conditions and must be built tough even if they aren't built most efficient.  With external regulation I have seen other types achieve outstanding efficiency.

I currently have a 6Hp lister with 2 of these alts on it driven off the one serpentine belt and it will pull both of them to full amps although it does seem to be close to it's limit and I have another 6.5 hp China Vertical Diesel also with 2 alts connected and it does them with relative ease. My little China hormonal Diesel was rated at 2.7 KW and it would pull one all day with the greatest of ease but that engine is bit of a power freak and will out pull the 6hp engines on my induction motor generator setup.  I never tested it with 2 alts due to difficulty of mounting but I'm pretty sure it would have done them to a pretty high if not full output.

I run the alts with belt drive and a 6" on the engine with the standard 2" on the alt works very well and allows the engine to run at a low revs and still pull a good load easily.  If one was only going to use them for battery charging at 30A or so, you could probably run an 8" pulley on the motor to slow it down and reduce wear and noise if you had a 6HP motor.  6 HP on any alt under 100A@12V is way more than they need.


My next experiment is going to be to remove the control circuitry and run the things direct both on the field voltage/ current and the 3 phase output and rectify it externally and see what AC I can get out of them.

I would LOVE to get a Leece Nevile  alt, particularly a 300A monster because there are external controllers available that can run them at 12, 24 and 48V output with VERY high efficiency.  Unfortunately while the controllers are reasonably priced, The cost of the alts here is very prohibitive so hard to justify for playing around with when I can get all these others for nothing.

As far as running disconnected from a battery, My experience is that this is not a problem most likely on any  alt made in the last 20 years especially for a short period of time.