External motorcycle alternators

[El Kevino]

I've heard some talk about using external alternators instead of the built-in ones. I know BMW has (had?) these on their bikes, but what about other manufacturers and models? I'm looking for something small, like 100W, although larger would be ok if it's cheap enough.

Thanks!
Kevin Edwards
University of South Florida

[El Kevino]

I've heard some talk about using external alternators instead of the built-in ones. I know BMW has (had?) these on their bikes, but what about other manufacturers and models? I'm looking for something small, like 100W, although larger would be ok if it's cheap enough.

Thanks!
Kevin Edwards
University of South Florida

[Travis Garrison]

Try forklift alternators (try your local alternator repair shop if you have one) for small and cheap...

Speaking from personal experience though (car I worked on at WWU used an external alternator), what ever you are thinking about it...don't do it http://fsae.com/groupee_common/emoticons/icon_smile.gif an external alternator is going to be heavy, and the belts a simply no fun to deal with.

-Travis
UW FSAE

[Sparky]

I have 2 questions what motor are you running? and is the alternator output from it so insufficient that it is worth the extra weight of an external alternator or would you be better off being more efficient with your electrical systems?

[drivetrainUW-Platt]

Didn't you guys at WW have your engine cover for your custom alternator pulley explode?

[Travis Garrison]

Yup...our driver hit the starter for the acceleration events, there was a pop....then no more starter...stupid mistake on the engine cover construction that no one cought.

It was a real heartbreaker...we had been running that motor on the dyno for more than a year (it was a 2 year car)...and the damn thing chose to go in Detroit...

We ran the alternator for a variety of reasons that shouldn't apply to most teams (dry sump in a tight engine bay)....essentialy I backed the car into a corner with the chassis layout and the engine guy had to get creative. Bottom line, like I said before...just don't do it. The lightest alternators we could find were still on the order of 5-10lbs that shouldn't have been on the car...and obviously you're introduce reliability issues.

Travis Garrison
UW FSAE
WWU Alum.

[jack]

if i remember correctly, the engine design judge really didnt like it because he thought it used to much horsepower.

[James Waltman]

It wasn't that he didn't like it. I just couldn't tell him how much power the alternator was costing us from the drag. I also couldn't tell him how much power the oil scavenge pump was consuming.

[El Kevino]

We're running an Intek Model 20. Alternator output is definately insufficient, almost nonexistant you might say. We need power to run our active intake and some other systems.

We already have a synchronous belt primary drive, so that's no problem for us.

Thanks for the tip on forklift alternators.

Kevin
USF

[rjwoods77]

Briggs engines have a ton of different stators. Call briggs and start asking around. They make a zillion different variations of that motor so they might have one that is used in something that requires a constant draw. All you really need is a stator that charges the battery faster than is pulls power out. On their bigger motors they have regulators that connect to the stator. Call briggs.

[El Kevino]

Answering my own question for people searching the forums in the future...

Suzuki Katana alternators are external and go cheaply on ebay ($30 or so). This is probably what we will use. Briggs does make an alternator kit for our engine, but it replaces the 13 pound flywheel with an 18 pound one! The Katana alternator weighs about this much, but with much less added rotational inertia. Plus, Briggs parts are very failure-prone.

[Travis Garrison]

We looked into the suzuki alternators...all I can say is they are heavier than they appear to be...dense little guys...The WWU guys could, if they weren't being lazy, walk across the shop and give you a part number for the lightest alternator we could find. http://fsae.com/groupee_common/emoticons/icon_smile.gif

-Travis

[Garlic]

Look into new or redesigned rectifiers to make your existing alternator more efficient. Otherwise, like you've seen alternators are generally pretty heavy items.

Active intake system on a Briggs? Isn't that sort of like having a Bluetooth equipped floppy drive? http://fsae.com/groupee_common/emoticons/icon_wink.gif

[El Kevino]

Well, if you were only allowed to use floppy drives, you'd probably eventually try to get one with Bluetooth.

With about 50 pounds/horsepower, intake development is more important on a Mini Baja than FSAE. We run wide open throttle about 90% of a lap. It's just that only USF has realized this and done something about it. This year we're developing a dual-length intake runner, electronically controlled.

The weight of an alternator is less important (although we still want the lightest we can get). If we pick up 1/2 horsepower and it costs us 10 pounds, we're still coming out ahead. In FSAE, a horsepower is only worth what, 8 pounds?

Why would stock rectifiers be so inefficient? What can be done about it?

Kevin Edwards
USF

[James Waltman]

El Kevino,

I didn't think you had any real freedom with the intake manifold in Mini-Baja. I thought it had to be stock after the air filter. So that must pretty much cancel out any effects of different runner lengths. And why do you want dual length runners. I would figure you would want to tune for the governor (3600rpm). Are you running something other than a CVT? What am I missing?

Just because the power to weight ratio is 8lbs per hp doesn't necessarily mean that it's worth adding 8lbs to get another hp. You have to turn and stop that extra weight too (and for a Baja car: pull it out when it gets stuck).

So on to the alternators:
http://dot.etec.wwu.edu/fsae/HostedPics/Alternators/3_samples_with_weight.JPG
I think that the unit on the far left is off of a Suzuki. Travis could confirm this. It weighs 7.85lbs as it sits in the picture. The numbers on it: 31400-06B00 and 100211-1940 and it says Denso on it.

I think that the one in the middle is from a forklift. It weighs 7.00lbs as it sits in the picture. It's from our local Automotive Electric shop (Whatcom Electric (360) 733-5051). Their internal part number is 23479 and the Mitsubishi number is A7T 30492. I think it is rated for 50amps.

The one on the right is off of our last car (Viking 35). It weighs 6.55lbs with that pulley. It doesn't have any numbers on it but it is the same one the V8 had. The numbers from that one are 23700KA110 and A7T 30374. It says Fuji Heavy Industries and Mitsubishi Electric Corp. I think it's rated at 40amps.

Lots more pictures here. (http://dot.etec.wwu.edu/fsae/HostedPics/Alternators/)

[MikeWaggoner at UW]

"With about 50 pounds/horsepower, intake development is more important on a Mini Baja than FSAE. We run wide open throttle about 90% of a lap. It's just that only USF has realized this and done something about it. This year we're developing a dual-length intake runner, electronically controlled."

Have you done it before? I thought it was against the "intent" of the rules to modify the intake; basically everyone is supposed to have the same powerplant.

[El Kevino]

Thanks so much, James!

The alternator on the right, does it come with that synchronous pulley? Can you tell me where I might source an alternator like it? Do all these alternators have built-in rectifiers?

We run a manual transmission, so a wide, usable powerband is important to us. CVTs are for golf carts! How many formula cars use one??

Of course, if you're coming out even on power-to-weight, it doesn't make sense. But in Baja, one horsepower can cost 20 pounds and still be worthwhile overall. Usually, improvements don't cost so much weight, though.

Yep, we've been doing intake work on our Bajas for the last 3 years. The rule says you can relocate your air filter. The carb must stay in the same place, but you can have a very funny-shaped pipe in between the filter and the carb. The intent of the rules is that you can't modify the engine. We don't - this is all bolt-on stuff with no internal engine mods.

Kevin Edwards

[jack]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> CVTs are for golf carts! <HR></BLOCKQUOTE>

...and Le Mans Audi's of course...

[Travis Garrison]

Ok, at the risk of dragging out a non-FSAE topic, I'll jump back in here for a sec...

Sorry to guilt you into that James. http://fsae.com/groupee_common/emoticons/icon_smile.gif

The left alternator is from a Suzuki, and no the pulley on the right doesn't come with it...Typically they'll come with V-belt pulleys...it's possible that one has a Gilmer belt simply because it runs off the dry sump pulley....but it might have its own drive...I can't remember..As far as the source for the smallest alternator...I'm pretty sure I heard the V30 guys mention a Japanese Subaru...Try tracking down alternators from the 600cc cars they sell over there...

Are you really picking up a horsepower? Unless you are actually increasing flow with the variable intake (which shouldn't be happening) you can't be making more torque can you (as compared to a non variable tuned length)? and since HP = torque x RPM (which is governed) / 5250 it seems like you are kind of stuck with what you've got.

So really you're just smoothing out the torque curve aren't you? Factor in that the external alternator is likely to sap more power than the stock setup and it seems like you are going to loose HP to me.

Can you mess with exhaust length? If so just do like many FSAE teams and set the exhaust for one resonance and the intake for another. If you're dead set on variable intake vacuum power might be a much more efficient approach to actuating it...or maybe even an old fashioned system of springs and weights....


-Travis Garrison
UW FSAE

[James Waltman]

Travis, the one on the far left has a helical gear. I think it is a direct drive off of the engine/transmission.

Kevin,
Do you have data to back up your modifications? (dyno?) Just asking out of curiosity.

I can't help you out with a source for the alternator. I had a new guy try to find a source two years ago and I literally had to dial the phone for him. The best he got was "some Japanese crate engine"�. He didn't come up with a source and I didn't bother looking any more because we already had one. If you really can't find it I can find out from some of the guys that did the V8 - they came up with them for us. I'll sell you the other two in the picture if you want them.

We made the pulley on the far right. It was simple really. We just bought the Gilmer pulley from a local bearing house. We cut out the center (cast iron) and replaced it with aluminum. I think it took Scott about a day to make it.

[El Kevino]

Thanks for humoring me, y'all. Baja people don't know much about alternators, and this is a good resource.

Tuned intakes can do more than smooth out a torque curve. They can move torque from a speed where it isn't used much and pile it up into the powerband. Why else would FSAE teams bother with them?

Yep, we have lots of data. Several years of dyno runs, plus WAVE simulations. Hee hee. I think we'll have the first Baja with a Ricardo sticker on the side!

We thought about a mechanical governor, but it's pretty cumbersome to do, although it could work fine. Vacuum is out because we don't have any (WOT all the time), although we could add a pump or compressor. We have several other applications for 12vdc, including a horn and a winch, that we haven't been able to have before. The winch especially is the reason we need more power. And why do we need a winch? I'll tell you in May...

Thanks, James, I'll start looking for that alternator. But the Suzuki will work and it's probably what we'll use this year.

Kevin Edwards