Exciting

[moe1942]

My son gave me his Bobcat 225G last year because the engine, an Onan, came apart. I am in the process of repowering this unit with a Kohler; only way to go. I know that the gen has probably lost its residual magnetism. What is the easiest, safest and OEM accepted method of excitation. The owners manual doesn't cover this or I overlooked it.

Thanks

moe1942

[H80N]

Moe
looking at the schematic.. it is an alternator with an excitation coil energized by the battery.. so should not need any static magnetism added.. initial excitation would be provided by the energized electromagnet formed by the excitation winding...
could be wrong but that is what it appears to be from a quick look..
hope this helps..
Heiti

[ASKANDY]

Depending on how old the unit is, Excitation came from a flashing circuit while starting through F2 and D4 diode. Once the engine starts, the excitation field is generated from the welder alternator winding which produces the AC to feed rectifier SR2 to form a closed loop.(DC in the rotor, ACout the winding to SR2 and back into the rotor) The rheostat privides the limit of saturation and varies the total output of BOTH weld current and Aux power availability. If you need to manually flash the unit, you may have a bad D4. You can otherwise flash the field at wire 33(-) and 24(+) to the battery.

Hope this helps.

Andy

[DDA52]

moe1942
Just curious, how easy were you able to get a shaft to match the original? Are there bolt hole issues? Just asking because my 225G needs a new engine as well. My main problem has been the shaft/rotor connection. Couldn't find anything to fit since the new Onans screw on. Mine bolts on. Finally found a new replacement Onan for $1500 with a 3 yr warranty. I never looked at Kohler since Onan gave me so much trouble matching shafts. Since I began my search, I have changed dealers. Answers are easier to come by now. Maybe Kohler would save me some $$$.

[H80N]

DDA52
there is a lot of variation in the way the crankshaft is machined on these engines..and a listed "replacement may not be a direct fit.... here is a link to a cross reference..

http://www.tulsaenginewarehouse.com/catalog/onan/guide/

if you are considering going the way that Moe has gone.. with a coupling.. you might consider finding a good used engine from a garden tractor.. lots out there with low hours and can be had for a song... usually need the carb rebuilt or replaced due to having had gas left in for the winter and the ensuing varnish and corrosion plugging the carb... $1500 is a lot of money.. and if you read all of the notes in the cross reference you may find that the replacement engine may not be a direct hookup anyway.. pay particular attention to the notes on which crankshaft is on your motor and which one is on the "replacement"....I think what Moe has done is a smart avenue.. and cost effective... you might find a good Kohler, Onan or even a Honda... locally that would do the job for you....
hope this helps
Heiti

[moe1942]

Excitation and engine swap

Thanks for the replies on excitation. Nice to know I have a knowledge base to draw on if things go South.

For DDA52. On the engine issue. I decided on Kohler because The Onan engine just isn't suited for welder application,IMHO. As Heiti said, Kohlers are plentiful. I got a low hour for $125. It's a Command 23 HP.

Coupling isn't difficult if you can get the necessary components. It is much easier if you alter the generator to be free standing. That way you don't have to tear the engine down and change cranks. I did it by using a AEA-200-L drive plate and bearing support. I machined a stub shaft to match the taper on one end and 1 1/8" X 1/4" keyway on the other.

DDA52. If you would like more details on this Email me. I can take some very close up pics which will help make it clearer. I may even have one of the parts you need.

Moe

[DDA52]

H80N
Thanks for the input. I checked out the link and found the same eng. for the same $$$. Shaft codes are identical. After reading Moe's reply, I'm going to do more checking. What's your opinion on the HP diff.? That is 16HP vs. 20 or 23HP? Not too many horses? I looked around here and all I could find was a 225G plus motor for $750. If I can safley and easily use a bigger eng., I might be able to find something else.

[DDA52]

Moe,
Couldn't email you through link on profile. I made sure mine was active/correct. I would definitely like details and pics. Email me through the profile link and let me know EVERYTHING! Well maybe not everything, just the good stuff!

[H80N]

DDA52
more horsepower could not hurt as long as it is developed at the same rpm... most of those engines have varying levels of tune and hp using the same basic block and components..anyway... so should bolt in the same way.. but check the one or ones that you are considering... the only drawback that I could see to going to more hp is a reduction in fuel economy.. but that should not be appreciable... as the welder will not use any more hp than it did with the smaller motor... if you are patient and look around.. am sure you will find a decent motor to replace yours... is yours worn out or broke... might consider a rebuild if just worn...
take care
Heiti

[moe1942]

Exciting

DDA52,

Can't add much to what Heiti said. More is better to a point. If you stay within the physical parameters, you can't overpower the unit. As Heiti said, the only downside would be increased fuel consumption.

I will try to Email you. We will get together on this. When your pockets aren't deep you get proficient at doing things on the cheap. Once I get your phone number I will call and give you more info. I can articulate better on the phone than in Email.


moe1942

[DDA52]

h80n
motor locked up and sat awhile - used different mach. is rebuildable but will cost $1600+

moe
got your email will respond this evening - gotta blast back to work now trying to beat rain

don

[H80N]

DDA52
if the engine is locked up just from sitting... you might try to remove the sparkplugs, squirt in a generous amount of one of the spray lubes like PB Blaster ... or Liquid Wrench .... then let it sit for a few days before trying to turn it over with a breaker bar...(may need to rock it back and forth gently to free the rings)... ATF and Kerosene will do about as well... if you are able to free it using this method..should be able to spin it with the starter till the solvent is pushed(sprayed) out of the spark plug holes and bores (will make a mess) then change oil and filter before trying to start it so that you do not pump diluted oil through it and blow it up that way... once it has been run and warmed up... would change oil and filter yet again before trying to use it...... one other caution.. it does need to sit and soak.. so be patient.. trying to move it prematurely can cause the rings to dig into the bores and you risk breaking rings... have seen this method work time and time again on engines that have frozen from sitting (even a few that had water down the bores..but the chance of success is slimmer and those usually need to be rebuilt anyway)... but if on the other hand.. the engine seized up while running.. then you have more serious issues... and might as well start looking for a different one....
good luck
&
hope this helps
Heiti

[DDA52]

Heiti,
Thanks for the procedure... Unfortunately my #1 piston and cylinder sleeve are rusted , fused , one piece and going nowhere. I won't mention the valves. Nope, that engine is in need of a major overhaul. The $$$ on that is why I was looking at a replacement eng. I'm gonna try to find a used one like Moe did. The price difference is just too big to ignore. I'll keep you posted. Thanks again.

Don

[H80N]

DDA52
well.... bet you will find a decent one if you look around a bit... as for the other info... might just tuck it into your hat for future reference... was worth a shot....
take care
Heiti