alternator questions

rcbeam · March 19, 2011, 03:44:03 PM

The P/O removed the 50DN and replaced it with a belt driven 75A 24V, driven off of the 2 belt camshaft pulley off the rear of the engine (flywheel end). The alternator is bad. I bought a used Bosch 150A 24V alternator from the local tour bus garage. On the newer buses they run tandem alternators. Anyway I have no mount that fits this bosch and also no pulley. The pulley on the 75A that I removed is too small for the larger shaft of the Bosch alternator. We have a small truck scrap yard here, but they don't have anything that is 24v as it seems all the trucks these days are 12v, or so the guy told me.

The previous alternator was attached to the frame rail on the rear street side with an adjustable rod to take up the slack in the belts, so it is not directly attached to the engine. I have no idea how the original belt driven 50DN was attached.

Does anyone have any words of wisdom in how to mount this alternator and also what size/type pulley etc and where to acquire a two belt pulley. These newer alternators all seem to be driven off of the large flat serpendine type belts. I don't know what size pulley I would need.

I'm stuck until I get an alternator installed.

thx,

Russell
MC8
Lexington Ky

luvrbus · March 19, 2011, 04:15:29 PM

Do you have a model number for the Bosch so we can look up the rpms needed to supply 150 amps,bar room guess it is going to spin 2.5 or 3 times the engine speed and fwiw the drive on the back turns the same rpms as the engine. These guys can help you with the right pulley for the Bosch www.blanchardelectric.com

good luck

rcbeam · March 19, 2011, 05:26:40 PM

Thx...I will try to get the model number Sunday afternoon. My next question is does it matter which way it spins but I guess a model number will help with that too. I've read that some matter and some don't but it seemed to revolve around the fan on the alternator rather than the alternator itself.

Russell
MC8
Lexington Ky

rcbeam · March 20, 2011, 02:21:52 PM

OK... got the numbers from the alternator.
BOSCH
0-120-689-552
under that is:
T1>>28V 70/140A
under that is:
Made in Germany

Only one label on the thing and this is it. Thx to anyone that can shed some light on this for me.

Russell

Just Dallas · March 20, 2011, 04:31:00 PM

Russell, Since no one else answered, I'll give t a shot, your generator is OEM on a lot of buses. It's a type T1 Bosch.

More info here:
http://www.saase.us/application_pages/Bosch_T1_Alternator.php

They can probably get the correct pulleys for you.

If not, Give Kirk's Auto up in Detroit a call 800.321.5989
http://www.kirksauto.com/

Quote from: rcbeam on March 20, 2011, 02:21:52 PM
OK... got the numbers from the alternator.
BOSCH
0-120-689-552
under that is:
T1>>28V 70/140A
under that is:
Made in Germany

Only one label on the thing and this is it. Thx to anyone that can shed some light on this for me.

Russell

rcbeam · March 20, 2011, 04:42:17 PM

thx Dallas... I'll check out the sites and see what I can come up with. I'm probably making this more complicated than it is.

Russell

luvrbus · March 20, 2011, 05:17:10 PM

Russel, that alternator uses a 3.0:1 to a 3.6:1 ratio it can spin up to 18,000 rpm without problems the trucks all use 3.6:1 because they idle for long periods

good luck

TomC · March 20, 2011, 09:11:13 PM

At 3.6 to one, the engine running up at 2300rpm will give an alternator speed of 8280rpm-a long way from 18,000rpm. I haven't ever heard of a alternator running that high. I know that the 50DN runs at 6500rpm max. Good Luck, TomC

luvrbus · March 21, 2011, 07:14:19 AM

Check it out on the Bosch site Tom I told Russell it could spin 18,000 not telling him to turn 18,000 rpm fwiw Prevost turns the 200 amp version at 3.6:1

good luck

TedsBUSted · March 21, 2011, 08:05:34 AM

It almost seems like 18,000 rpm would have to be a typo.
That just seems way beyond the practical design limits of a common large rotor.

Maybe 8K?

Ted

luvrbus · March 21, 2011, 08:25:00 AM

I don't know if it is a typo or not they sure make reference about the bearings and other alternator manufactures max rpm,new Delco alternators are high rpm now also they are supposed to be more fuel efficient in the long run according to all the manufactures

good luck

rcbeam · March 21, 2011, 03:59:42 PM

lubrbus that is good to know. Thx for the ratio info. Now I have no clue how to relate 3.6:1 to pulley size. Is this just a simple math problem and I'm having a brain fart or is it more complicated. Would the cam shaft pulley be 3.6 times the circumference of the alternator pulley?

Russell

rcbeam · March 21, 2011, 04:05:09 PM

I think I may have answered my own question on the ratio. I googled "calculate pulley ratio" and found a site.
I uses the pulley diameter, not circumference. So I guess the driving pulley would be 3.6 times the diameter of the driven pulley.
Whatcha think?

Russell

RoyJ · March 21, 2011, 05:05:43 PM

Quote from: rcbeam on March 21, 2011, 04:05:09 PM
I think I may have answered my own question on the ratio. I googled "calculate pulley ratio" and found a site.
I uses the pulley diameter, not circumference. So I guess the driving pulley would be 3.6 times the diameter of the driven pulley.
Whatcha think?

Russell

Diameter, radius, and circumference of a circle are all linear in relation ship. Therefore, you can use any one of the three when calculating ratios.

You calculation is correct; find an alternator pulley 3.6 times smaller than engine pulley.

luvrbus · March 21, 2011, 06:05:05 PM

Russel the pitch of the belts come into play when figuring the ratio also I know the drive pulley is a little over 6 inches in dia and is 1:1 drive , but I forgot what the pitch (angle)is on the drive and you will need to know that to get the right ratio pulley then Kirk's or Blanchard can furnish the right pulley.
Any of you guys know what the pitch is ?

good luck