10SI Project

[veggie]

squarebob,

I really like that Petter setup that you built. Very compact.
That's exactly what I have in mind for my little air cooled 165 Changfa and Delco 12Si.

How does the engine react when you switch on the alternator load.
Does it really bog down or just give a puff of black smoke and bark a little ?

veggie

[squarebob]

Everyone talks about stalling out their engines with too much load. No need to spin the alt at 5000 rpm if the engine can't handle the load. I sized the pulleys to not overload the engine. The engine puts out 1 HP per 1000 RPM. I slowed down the Alt. RPM based on the performance curve I have for the unit  (see attachment). The engine is variable speed so I can run the alternator RPM from about 500 (and 0 output) up to about 2000 RPM. Now the fastest I can get the engine to run with a battery bank that needs a lot of charge is about 3000 RPM and 1725 RPM on the Alt. It puts out about 35 Amps at 28 volts and a little gray smoke from the exhaust. As the bank charges up and the Amps drop, I can slow the engine down to match the needed output and save fuel. I built this as a charger to take my bank from about 80% to 100% and as a backup to my GM90 setup.

Bob

[veggie]

Nicely done !

veggie

[cujet]

  I have been out standing in a bunch of fields!!!!

That's perfect, I'll have to remember that!

Great project. I've been wanting to do something similar, so this is all very interesting to me.

[squarebob]

Well the direct drive worked good during the testing phase but I did not have a set of GC batteries to really put a load on the system

[squarebob]

When I hooked up a REAL battery that needed some charge, the little engine just struggled too much with the load. So I changed it from direct drive to pulleys. I went with a 3" on the engine and a 4" on the Alt. So now the Alt is turning at 75% of the engine RPM. Well that really made the little engine happy. It is not overloaded, I can run the RPM down and it runs fine. I am able to pull 50 AMPS at full throttle and I think that is pretty good for this setup. Remember, it's just a 99cc Harbor Freight engine! Now I need to finish up the wiring and the gauges and such so I can get the system online at the flying field.

[veggie]

squarebob,

That's a great looking unit. You did a nice job there !
Where did you acquire the vibration isolators ?
(part number?)

cheers,
veggie

[squarebob]

cheap cheap cheap

ANCHOR Part # 2393 Trans Mount

Rock Auto - $3.68 each

Fleabay - $3.17

Other places also

Bob

[BioHazard]

Great work, just like before. I guess my little 79cc HF engine won't have the balls to direct drive either. I think I'll try a bigger engine with the direct drive setup....

[Tom Reed]

I'd like to see a bracket off the outside bottom bolt back to the mounting plate. Looks like there will be a lot of twisting force on that standoff.

[ryanw95]

SquareBob - how long are the bolts (threads) coming out of those rubber isolators (trans mounts)?

[squarebob]

Tom, Thanks for your concern. The bottom standoff is 1" diameter round stock with a 5/16" hole drilled through for the 5/16" bolt. It is solid as a rock.

Ryan, the bolt coming out of the mount is just shy of an inch long.

Bob

[BruceM]

Great job on the nice looking charger, SquareBob, at an amazingly low cost.  I hope all the other RC'ers in your club will appreciate your effort greatly. 

Happy Landings,
Bruce

[squarebob]

Project Update: The system is completed and installed. I added a 85W solar panel and made a tracking mount for it also. The project is a success and the club is enjoying the system a lot.

[LincTex]

I slowed down the Alt. RPM based on the performance curve I have for the unit  (see attachment). The engine is variable speed so I can run the alternator RPM from about 500 (and 0 output) up to about 2000 RPM.

A lot of folks caution against running the alternator too slow due to decreased fan speed/cooling air flow.

How hot does your alternator get under load when spinning so slow?