Slow Speed Changfa Project

[veggie]

Here's how the weights look....

I calculated the kinetic energy in the current flywheel at 1500 rpm. (Where the engine runs very smooth)
and then increased the weight of the flywheel until I got the same rotating kinetic energy at 900 rpm.

16.75" diameter @ 1500 rpm @ 14,949 lbs.force = 80lb. flywheel

16.75" diameter @ 900  rpm @ 14,949 lbs.force = 221 lb. flywheel

I presume 221 lbs. would be an unrealistic weight to place on the crank bearing.
Any suggestions as to what would be an acceptable weight.
Perhaps an additional 60lbs ?

veggie

[veggie]

rcavictim,

When you experimented with the large flywheel. Did it actually make a positive difference?  (before it broke).
Did you achieve a slow running diesel with reliable quiet power?
Other than the bolt boss failures, would you consider it a success?

veggie

[mobile_bob]

i would think you could get by with maybe 100lbs, if you use an overhead mounted alternator
where the belt tension can help to carry the additional weight.

60 lbs is probably a nice conservative number, especially in light of the fact we don't know what the
oil pressure is in a well used 195 when it is hot, running at 900rpm.

surely the overhung alternator could offset the addition of 60 lbs without any issues i would think

60lbs would probably be all that is needed, using your illustrated design, where most all the added weight
is at the periphery of the oem flywheel.

one interesting thing i like about your added flywheel design is the fact that it would be easy to have the
machinist add the serp belt grooves, and i would suggest 8 groove automotive.

that would be very cool, and i might even want to buy one, so let me know before you do the machining
because it might be cheaper to do two or more than a single unit.

i would have to rethink a few things, but i might well want one too.

bob g

[rcavictim]

rcavictim,

When you experimented with the large flywheel. Did it actually make a positive difference?  (before it broke).
Did you achieve a slow running diesel with reliable quiet power?
Other than the bolt boss failures, would you consider it a success?

veggie

I'm still using the big flywheel but it is now coupled via the factory dual B belt shieve on the R175 to a larger pulley on the jack shaft with bearings that hold the big flywheel.  The large flywheel runs at 1/2 crankshaft speed so as to not exceed it's rim speed rating when I operate the R175 at 1800 RPM to drive a 4-pole alternator.  The engine can be slowed way down and runs smoothly below the point where my oil pressure indicator mimics a penis in a cold swimming pool at which time I have to speed up the rig or shut it off.  The R175 is not a powerful,engine even at the rated 2600 RPM and at that speed is only good for making about 3 kW of E power.  At 1800, I can coax 2 kW out of this rig.  At a nice slow 900 RPM or so it is a treat to listen to and makes 500 watts or maybe more at greatly reduced voltage and frequency. I cannot give you an exact number on how much.  The little bit of give in the belts totally eliminates the peak parts breaking torque while still pulling the engine through the draggy parts of the cycle at the lower RPM's where there is insufficient momentum storage in the stock, rather small flywheel.  The large flywheel keeps the output power completely free of any flicker, even at the really slow RPMs and gives the genset much better motor starting short term output surge capability than I would otherwise have.

If I were to operate the rig at the really slow speeds more often that for occasional curiosity I'd definitely want to retard the fuel injection pump with a extra spacer between the pump and the engine block.  You can really hear that diesel knock as a sharp whack on the poor lower rod bearing and crank journal at the low speeds.  I have run that little engine at ~400 RPM with the flywheel in the system and it is remarkably smooth.

I have improved the splash lube in my R175A crankcase by adding a dipper/thrower onto the lower rod bearing bottom bolt.  It does a way superior job of getting oil onto the crank ball bearings and camshaft. I read of JiangDong 175 owners having their main bearings weld up solid in just 12 hours.  Having been inside mine a lot I came to the conclusion that the factory oil system needed help.  I have had no bearing troubles with my engine that go my oiling system modification very early in it's life.  The R195 that you have is a totally different layout lube wise as is my new Changfa 1115.  My plan for the 1115 is most likely to run it at 1800 RPM direct coupled to a 12 kW 3-phase ST type head as soon as I can obtain a gen head. I won't need to fiddle with added flywheel mass on that project.

[Henry W]

Based on the comments from Bob, rcavictim, and jlmtech, I made the following modifications...
Any other suggestions before I begin calculating the overall weight required and finalizing a machining drawing ?

(It appears the weight for the flywheel will be determined by the crank bearing carrying capacity.)

veggie

Nice idea Veggie.

I would recommend putting three 3/8 dia. dowel pins 120 deg. apart between the bolts. Press fit in the new pulley face. They only have to go in the flywheel face 3/8 deep. This should eliminate shock and additional stress on the bolts.

Henry

[Henry W]

Once they are mounted on the flywheel I would recommend sending the complete assembly away to get ballanced.

Henry

[rcavictim]

Nice idea Veggie.

I would recommend putting three 3/8 dia. dowel pins 120 deg. apart between the bolts. Press fit in the new pulley face. They only have to go in the flywheel face 3/8 deep. This should eliminate shock and additional stress on the bolts.
Henry


[/quote]

Yes you would think it should, but it wont.

[veggie]

Have you considered increasing the flywheel diameter - that will give you more stored energy for a lower weight.
I personally would prefer running a second flywheel on a jackshaft and have the two interconnected with a belt but that is just my take on things and part of the attraction would be the ability to run multiple devices off the jack shaft via seperate clutches. The drawback of course is the extra size of the resulting machinery.

Hi Jens,

The unit was built with compactness (is that a word ?) in mind.
My accessories are driven from the flywheel, so if possible, I would like to maintain the diameter.
By going larger in diameter, it would negate the existing frame structure and accessory mounts.
We'll find out when version 1.0 gets "first smoke".
If I need to go with a larger diameter, I will accommodate it somehow.

veggie

[veggie]

Jens,

Perhaps I could go larger in diameter, but it would mean scrapping the belt guard and making another.
Fitting a new one would also mean welding new mounts to the base.
If I find it necessary to go bigger in diameter after testing version 1.0.0, then I suppose I could do these mods to accommodate.

veggie

[veggie]

I removed the flywheel ready for the machine shop.
The flywheel was weighed at 68 pounds, so my plan to add another 60 lbs will almost double the flywheel mass of the unit.

veggie

[veggie]

Bob,

When you suggested .002" per degree of ignition timing...

1] where exactly do the shims go? (At the joint indicated by the arrow in the picture below?)

2] I assume we make the shims with .002" shim stock and scissors ?

veggie

[mobile_bob]

yes they fit in right there, i made mine from notebook paper and scissors


you just have to be careful that the governor link connects properly into the slot
on the pump when you go back together, otherwise you can have a runaway.

its not difficult to do the job at all, just wanted you to be aware of the link

some engines have a small removable cover that you can look through to see if the link
is in proper placement with the pump.

my idi changfa's do not have such a cover, my di flying fish brand engines however do have the little cover.

bob g

ps. went back and took another look your engine gear cover doesn't have the little cover, much like my changfa
so just look up inside as you install the pump and you will see the little link/pall and how it fits the slot in the pump

btw, can you take a picture of your cylinder head from above, showing the injector and post it?

[Henry W]

Hello Veggie,

Did you get a manual with your engine?

Henry

[Henry W]

If you don't have one I'll email you a photo copy of one.

Henry

[veggie]

Hello Veggie,

Did you get a manual with your engine?

Henry

My manual simply says "to retard the timing add shims". 
Very descriptive !

It also states that TDC is when the mark on the flywheel lines up with the mark on the hopper.
My engine never had a hopper ! Hence no TDC indication.