GM 90 cogen project

[mobile_bob]

i think the fuel consumption numbers a on the optimistic side, and likely not even close to the reported
numbers at 80% of rated full load.

figure on about 15-20% higher consumption numbers to be safe if you will be running at 80% of rated load.

Ronmar's report of 140kbtu per gallon (US) is a good number as well, and fits with references i have.

bob g

[DRDEATH]

Square Bob if you have not already thought of it. Hockey pucks work real good for starter wheels. Very cheap also. Just an FYI. I will share  from experience you want whatever you use for friction to be as close to the starter as possible. Lots of torque way out on the shaft. I did the same thing and now I am building a support which helps support the end of the starter shaft. DD

[squarebob]

Thanks for all the replies. I don't know where I came up with 130,000 btu. (brain fart?)

DD, how do you attach the hockey puck to the shaft? got any pics?

Ronmar, I am using the belt drive pump that came with the engine for now. May go with a Taco type later.

Bob

[Crofter]

I found the starter I am going to use . It is a 1 Kw, 20 pound unit from an early 60s Ford truck. Good flanges and a nice long shaft for the drive roller. Bigger balls than the B&S Starter I was looking at. Cost is 39.99.

Bob

Good unit and easy to work on. Also easy to modify to a ball bearing to replace the oilite bushing on the output.  Yes, long shaft but remember that the drive gear when engaged was right in next to the endplate. Original gearing was 10 to one or greater so a hockey puck size or a bit smaller running on the rim of your flywheel may be a bit less reduction but will be no problem running the engine up on compression release. To crank without release you might need to back the engine off but it will really be forcing things the first few compression strokes. I would plan on building in a support for the end of the shaft as a friction wheel will most likely bring the force out several inches from Fords design.

If you use a bit of creativity on where you put the fulcrum of the swing mount you can make it virtually self engaging after initial contact. Make the reaction torque pull the friction wheel in rather than repelling it.

[Ronmar]

Ronmar, I am using the belt drive pump that came with the engine for now. May go with a Taco type later.

Well if you have read much on these forums, there are some mixed feelings on those belt drive pumps.  Some have run them with no problem, some have had them self destruct overnight.  I havn't had my hands on one in person, but the last discussion I read had teardown pics, and those just didn't show a pump put together quite right IMO.  Knowing that, If it were me and I was contemplating using a pump, I would make plans for a small taco sooner than later...  But since all the primary loop fluid flow can be done on this engine without a pump, I never even considered a pump for that.  I do use a small taco on the secondary loop, which works very well.

[squarebob]

If thermosiphon works on the primary loop with a heatex, I just may " dump the pump" idea and just use a taco on the secondary side. I was under the impression I needed a 55 gal drum for thermosiphon to operate correctly. Looking back on some of yours, and other posts, I see I am mistaken.

Bob

[Ronmar]

My system has exactly 2 gallons of primary coolant, including about 1" in the expansion tank.  With so little coolant volume, the system needs to be oriented vertical in order for the density change to have enough energy to power the system.  My avitar is a scale drawing of my system.  When standing at the level of the engine mount bolts, the heat exchanger is at eye level.  A larger coolant volume would need less height to function.  The heatex is a brazed flat plate type 5" X 12" X 10 plates.  These have very low flow restriction so are perfect for thermosiphon.  Their design also makes them very efficient so a little heatex goes a long way:)

[XYZER]

My friction starter w/leece neville. I got my wheel from mcmaster carr. I might do it different on the next one.



In action......
http://www.youtube.com/watch?v=_QmWXNo-Gmg&feature=channel

[squarebob]

Great video of the starter. Thanks. What are you using as vibration isolation units. They seem to be doing a great job.

Bob

[XYZER]

Great video of the starter. Thanks. What are you using as vibration isolation units. They seem to be doing a great job.

Bob

I used 4 transmission mounts out a early volvo. A walk down the engine mount isle in the friendly local auto parts store gave me some good choices. A good balanced engine also helps.

[veggie]

squarebob,

Your GM90 has the spoked flywheels so I'm assuming it has the 750 rpm governor spring.
At 750 rpm your engine is rated at 6hp.
You can therefore set up a cooling system based on any Listeroid 6/1 information that you can find in this (or other) forum(s).
In my case I use the rule of 1/3 rds. the same as Ronmar suggests.
6HP = 4.47 KW mechanical out represents 1/3 of the total energy created by the fuel.
There will also be ~4.47 of heat rejected by the cooling system.
Based on 3412 btu's per kw:...
4.47 kw X 3412btu = 15,251 BTU's of rejected coolant heat.

If you size the cooling system for 16K BTU or greater, you should be ok.

Nice project.
Please keep us posted.
Veggie

[squarebob]

Thanks Veggie.
I was looking thru the manuals today and one says to adjust the valve lash cold and the other one says to adjust it hot. Any suggestions?

Bob

[Crofter]

Thanks Veggie.
I was looking thru the manuals today and one says to adjust the valve lash cold and the other one says to adjust it hot. Any suggestions?

Bob

With pushrod enclosed overhead valve engines it use to be considered that hot lash would be less than when cold. With this style of engine and long exposed pushrods there may not be much difference from hot to cold. The main concern I would say is to be sure that your valve clearance is not on the tight side. Set it cold and check it totally warmed up and see if there is any difference. Choose the setting temperature that gives the larger hot setting. What are the recommended clearance settings by the way?

[veggie]

Cold setting for the GM90 is:

Inlet:      0.250mm  (0.010")
Exhaust: 0.350mm   (0.014")

veggie

[Crofter]

Jens, there is supposed to be a special place reserved in hell for those who sit on the fence in times of crisis! 

That recommended clearance seems quite liberal. I think the older listeroids 6-1 called for .017" and the 1000 rpm ones .008. but we cant assume that the valve to piston head clashing geometry is similar on the Satyajeets. Some engine arrangements would have the pistons slapping the valves if lash is set too tight. JohnF has mentioned finding cam lobes pinned five or more degrees off spec. so dont err on the tight side. The GM90s might be to more predictable standards but I havent heard a lot about rebuilds and teardowns so far to compare.

Expect to have to reset the lash a number of times as there are a lot of not too well finished surfaces within the valve train which will have to lap into each other before they stabilize and hold the settings