Author Topic: Slow speed use of larger Changfa  (Read 5199 times)

rcavictim

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Slow speed use of larger Changfa
« on: July 24, 2006, 05:07:19 AM »
I have been studying the Listeroids and Changfas now for some time with hopes to obtain an engine or two as meager finances allow.  Being on a tight budget has got me thinking about purchasing a way over sized Changfa rated at say 20 HP @2200 RPM (like a 1115) and using it at perhaps 1/3rd of that speed where I guess the available HP may be around 25% or 5-6 HP.  That could power a 2-3 kW head.  This engine is close to the displacement of a Listeroid (around 1.2 vs 1.4 litres displacement).  If the Listeroid was capable of safe operation and efficient breathing to support 2200 RPM, it would put out 25 HP too.

The only worry I have without having a priori experience with Changfas is guessing that the flywheel supplied is going to be insufficient to carry the load smoothly at such low RPM, or even the engine ticking over smothly.  In my case the load would be a small gen head like an ST rated at 2-3 kW and 1800 RPM driven by a betl system.  I was thinking of putting a speed rated flytwheel on the high speed generator shaft.

The benefits of a heavy flywheel have been dramatically demonstrated to me while working with a DIY 1.5 litre VW diesel genset directly driving an ST type head at 1800 RPM where the factory flywheel at this low speed is no more than a carrier for the starter ring gear. Pulsations in the AC power due to fraction of a turn velocity modulation of the rotational speed, and attendant flickering of lights can be seen if one injector of four is not quite firing smoothly.  On the other hand, the truly massive flywheel on my one cylinder Petter (yeah, I scored a real one) can carry a rated electrical load even if the engine is shut off for a few seconds by slamming the fuel rack shut.  The power from this puppy is smooth, and the reserve for starting overloads is huge.

Seems to me that by operating a Cangfa at 1/3rd to 1/2 rated speed and lightly loading it would greatly extend the service life of such an engine, providing that it was thermostatically controlled and was processing enough fuel to stay at operating temperature and not run cold.

I'd be interested in any comments on this idea.  I have seen some of the discussion dissing the Changfa as a short lived engine.  It looks heavy to me.  If you completely blueprinted and balanced a Lister CS to be safe at 2200 RPM it wouldn't last as long as a Changfa I'd wager!

I am excited to have just discovered this forum and think it is right on topic for issues I am now dealing with in a serious way as I try to deveolp energy systems on my rural estate to assist in energy efficiency, self dependance and survival.
-DIY 1.5L NA VW diesel genset - 9 kW 3-phase. Co-gen, dual  fuel
- 1966, Petter PJ-1, 5 kW air cooled diesel standby lighting plant
-DIY JD175A, minimum fuel research genset.
-Changfa 1115
-6 HP Launtop air cooled diesel
-Want Lister 6/1
-Large DIY VAWT nearing completion

rgroves

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Re: Slow speed use of larger Changfa
« Reply #1 on: July 24, 2006, 10:56:43 AM »
This is a project I've thought about too, and here are my reservations based on working with a 195 and 1115.

Yes, Changfa flywheels lack weight and diameter of a Listeroid. These engines have a counter balance shaft, a vibration dampening feature a Listeroid doesn't have.  At idle RPM they jump around to the point their power impulses are going to be destructive.  Up around 1000 rpm they smooth out a lot.

 A new engine needs to be worked hard, to seat the rings properly. 

I'm concerned about the Changfa maintaining enough oil pressure to keep it properly lubed at such a low RPM.

If you're driving a generator, you need steady rpm and I don't think the Changfa governor is designed to do that in an idle speed range.

And finally, I haven't found a torque curve to show me how much useful torque a Changfa will make at that speed.

If anybody here knows these answers from experience, please speak up.

Older model Changfas of the 195 class made their rated power at 2000 rpm, newer ones are rated to 2200.
Run one down around 1500 and it would last a long time. Other factors permitting, I think 1200 would be even better.

rg
A country boy can survive - Hank Williams Jr.

mobile_bob

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Re: Slow speed use of larger Changfa
« Reply #2 on: July 24, 2006, 03:11:09 PM »
 i would agree with russell in re to all his concerns

i have a 195, and it runs pretty smooth and markedly quieter at 1500rpm

below that and while it may be even quieter it gets to shaking pretty harder.

the drive i am working on is ratio's to allow the engine to run at 1500rpm, i think that is a pretty realistic low end figure

bob g
otherpower.com, microcogen.info, practicalmachinist.com
(useful forums), utterpower.com for all sorts of diy info

Jim Mc

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Re: Slow speed use of larger Changfa
« Reply #3 on: July 25, 2006, 03:57:42 AM »
Seems to me that by operating a Cangfa at 1/3rd to 1/2 rated speed and lightly loading it would greatly extend the service life of such an engine....

I'd be very careful about basing this project on that assumption.  I'm no Diesel engineer, but I'm pretty sure that an engine designed for 2200 rpm is going to suffer some degradation when operated at half speed or less.  As has already been mentioned, the balance isn't right, I'm sure injection timing would need to be tweeked, and who knows what else...

The flicker problem could be worked, with a decent electronic regulator, but I wouldn't classify that as an easy design problem, either...

rcavictim

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Re: Slow speed use of larger Changfa
« Reply #4 on: July 25, 2006, 07:00:09 AM »
Seems to me that by operating a Cangfa at 1/3rd to 1/2 rated speed and lightly loading it would greatly extend the service life of such an engine....

I'd be very careful about basing this project on that assumption.  I'm no Diesel engineer, but I'm pretty sure that an engine designed for 2200 rpm is going to suffer some degradation when operated at half speed or less.  As has already been mentioned, the balance isn't right, I'm sure injection timing would need to be tweeked, and who knows what else...

The flicker problem could be worked, with a decent electronic regulator, but I wouldn't classify that as an easy design problem, either...

As an lifelong advanced tinkerer and DIY'er now graduated to my 50's I have no quams of taking just about anything made and re-evaluating it's potential to be modified or applied in ways not necessarily intended or conceived by the designer.  In many cases the over asked question "Will this work?", can only be answered difinitely by actually setting up hardware and applying the power.  Sometimes it is even wise to apply the power via a long extension cord. Intuitively knowing the proper length of that cable is where experience really comes into play.  ;D

I respect the valid concerns and comments I've received by those who have some good background here, but who haven't actually taken my idea through a full R&D trial.  Such a trial might involve a large flywheel directly driven from the crankshaft by a flex coupler (to break potential crankshaft resonance issues) instead of putting a flywheel on the other end of the drive belt as I had suggested on the alternator itself.  I could see this perhaps helping smooth the low speed vibration concerns mentioned.  Compliance of the coupler would have to be addressed to fine tune the system I'm sure.  Dink with injector timing?  By all means!  Modify the governor to work better at low speed?  I expected to have to do this but didn't mention it.

I have a big DC generator, 400 amps continuous at 50 VDC when spun at 1800 RPM.  That's 20 kW.  It is huge and weighs maybe 850 lbs. The commutator brush gear is impressive.  I want to get a diesel engine coupled to it for use as a welder and possibly battery charger once I'm less grid dependant.  A 1.6 L VW diesel or the 1.7 L. Nissan diesel I have still in a car would be perfect but I don't have the inclination or time to put such a project together with all the other projects that I need to finish.  I spent many months winter before lastr fabricating a 10 kW, 3 phase genset using a 1.5 litre VW Rabbit diesel and that was a LOT of work. George profiled my effort on his Utterpower website.  I want a simple solution and purchasing a 1115 Changfa which already has a fuel tank and cooling system and can be plunked down on a simple frame seemed like a possible fairly painless route to welding capability (I don't need more than 10 kW welding current).  If I purchase one as proposed I can also experiment with it and see how it likes reduced RPM operation when time permits.

So who will be the first to explore this reasonably in depth?

Jim Mc,
The flicker problem with the VW only happens on incandescent lamps and is not noticeable on newfangled compact fluorescents, BUT is a symptom of the engine not running properly.  Right now my VW genset is running flicker free.  I used it for several hours last week during a all night long storm outage to keep my house and air conditioner alive.  Remember the VW is a hiugh speed engine.  It is designed to rev.  Torque peaks at 2500 RPM but HP grows to 4000 or so.  Using it at 1800 directly driven it consumes less fuel, wears out slower, is quieter, etc.  It gets fully respectable fuel consumption numbers near 30% of fuel to electrical output at my 1650 foot ASL elevation.  The flywheel is totally inadequate as I mentioned because the engine is not designed to be driven at that low RPM in the car.  I think the fact that I can get smooth power at all, especially with a 3-phase alternator, speaks very higly of the VW engine.  I have to say I am inpressed.  I routinely place a wooden block in the governor linkage and run the plant at 1200 RPM into electrical space heaters and incandescent lamps to heat my shop with co gen coolant and some exhaust heat going into the building.  The engine runs really smoothly and quiet at 1200 RPM (40 Hz) but doesn't make a lot of heat.  This is my fuel miser mode for that genset which makes heat and light in the shop but not powering any 60 Hz voltage critical loads.
-DIY 1.5L NA VW diesel genset - 9 kW 3-phase. Co-gen, dual  fuel
- 1966, Petter PJ-1, 5 kW air cooled diesel standby lighting plant
-DIY JD175A, minimum fuel research genset.
-Changfa 1115
-6 HP Launtop air cooled diesel
-Want Lister 6/1
-Large DIY VAWT nearing completion

okiezeke

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Re: Slow speed use of larger Changfa
« Reply #5 on: April 27, 2007, 05:18:43 AM »
Sparky,
I'm in the process of trying something similar.  I have a weichai 1115 rated 26hp at 2200rpm.  Im going to direct couple to an ST15.  I'm  sure I wont make 15kw, but will be happy with 10.  Havent started the engine yet, but looks nice on the outside.  Getting thermosiphon kit from George, will prob use a small car radiator.  Most folks say changfa types run well 1500-1800 so I'll see soon.  Good luck on your slower speed project.
Zeke
Changfa type 25hp with 15kw ST head
Lovson 20-2 in blueprinting/rebuild
International TD-15 B  1962 dozer
Changfa 8 hp., 280 A battery charger