Alternator speed on 8V engines

Short story, I run the track GRiSO to the red line constantly, and am a bit concerned about the integrity of the field windings at these speeds. Sure they can handle the occasional excursion to theses high revs,  but to hold this constant high rpm , hmmmmm .......... I don't want to be the first to report an alternator tearing apart a fuel tank, Last time I checked, fuel and elecricity are not to friendly, that's why we confine it to a very strong chamber and use the energy to push Pistons down etc etc.
So , the standard set up runs the alternator to 14240 rpm at red line ( 8000 rpm ) the drive ratio is 1 : 1.78

I'm installing a smaller drive pulley with the drive ratio of 1 : 1.08 , so max alternator rpm will be close to the engine speed. 8640 rpm in this case.


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If the alternator goes through the tank, it will no longer be alternating as it passes through.....

Passes through me or the tank

Ron, since it's a track bike why bother with the alternator at all? It's a huge dead weigh The! Piss it off, fit a LiFe battery with sufficient CCA to start it if it stalls on the grid but start it in the pits with a jumper pack, if it's still got lights disconnect them and you've not only obviated the need to worry about the bearings reaching their speed limit you've shed the weight of the alt, the belt and the front pulley. Shit, you can save a few grams by taking the belt cover off too if you like!

Pete

Plus they only take 10 minutes to charge to something like 80% capacity.

I'm a bit concerned about the voltage dropping to a point where the ECU says "no more"
I'm only out for about 15 minutes plus a couple minutes waiting time.
I Guess the only way to find out is to try it

2 x LiFePO4 batteries will give you ample capacity. Hook em up in parallel, after getting rid of the alternator. Less weight, more fasterer!

Generally speaking, the voltage doesn't drop that much. You'll get full juice, then...nothing. You'll just fail to proceed. The ECU won't know what hit it. Arse might be involved, so..Tony? Yay or nay? You know more about batteries than I.

When Rob and I were racing our old Tonti it had a constant loss system. LiFe batteries weren't around then or at least weren't available for any sort of price we could afford. Rob used a quite small Gel battery for racing and we used a bloody great booster pack to start it. Early in the piece we also removed the starter after the engine was going and fitted a plate over the hole. That saved us a bit more weight but meant you DIDN'T stall on the start line unless you wanted to be really embarrassed or run over when the flag fell

Races were ten-fifteen minute affairs, Rob never ran out of juice unless he fell off and the lanyard killed the ignition!

pete

Ok , let's do it, Alternator will do Zero rpm sitting on the bench
I'll do some test running and measure current draw.

The removed bits. Alternator wt 3.2 kg, pulley, belt and bits 452 grams. Mr Andersons plugs will help out to make a couple of quick change out Batteries.

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There be a hole now where bits came from. The cover will go back on for prettiness  
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I expect to hear of faster lap times.


Want a 10000 RPM limit?

Real, real world progress is made.

Just a warning with LiFePO4 batteries - if you completely discharge them they may not recover - that's why I suggested 2 in parallel.

Biggest killer of any battery after charging system fails (or is removed) is the headlight. 30 min max.
Remove all lights and you will have an hours riding plus.
If you use a jump pack for starting, a single battery could last you 8 sessions.

You can borrow my 1kg Shorai for testing purposes.

Oz1200Guzzi wrote:

Real, real world progress is made.

Just a warning with LiFePO4 batteries - if you completely discharge them they may not recover - that's why I suggested 2 in parallel.

Good to know Tony, researching sizes now.

[quote="ghezzi"]Biggest killer of any battery after charging system fails (or is removed) is the headlight. 30 min max.
Remove all lights and you will have an hours riding plus.
If you use a jump pack for starting, a single battery could last you 8 sessions.

I was thinking 2 batteries, one in the bike, one on charge between sessions
No lights on this one, but don't forget, we still have a Fuel pump, ECU, injectors etc. I have a volt/ammeter to connect up tomorrow to measure draw.
Fired it up this afternoon, after a bit of a warm up the throttle response is a bit sharper, can't wait to try it out

I use an SSB PowerSport battery from Batteries Direct, and a 14A/Hour version. This has heaps of CCAs (425 to be exact) which is way more than the 20 A/H lead acid that was originally in it. You could use a 14 A/H, 16 A/H or go all the way and use a 20 A/H battery.

From memory, you could possibly stack one over the other in the space allocated on the GRiSO (probably the 14 A/H).

A 20 A/H would see you through a 20 minute session quite easily, especially if you used another to boost it while starting... (read jumper leads , or as you already mentioned, Mr Anderson's plugs, one with a connection to the outside world to be used for starting and also for re-charging).

You will know when the battery voltage is getting low (it won't just cut out) by the irregular sparking and running of the track special, possibly even backfiring. Get it (the engine) hot enough and yo won't need a spark (kinda like a diesel...)

Let me know if I can add anything further on the battery front, the rest is bullshit from me

I called SSB powersport about a Lifepo for this , their response was that a 14 BS has loads of CCA but only around 4 amp/hours capacity, and over $300 each. , A AGM battery of 14 A/H is $88 each.
So , I'm going to run a couple of these , one on charge,  one on bike. The Li battery will be used for the starter only via a 175 amp Anderson plug mounted near the starter.
Peaves me to go back to these, they are about 2 kg heavier.
Ps: I think the rating they give the LiFePo batteries is to show what size lead acid battery they replace, not an actual A/H rating.

How much does the rest of it pull in the way of Amps, Ron - you need to put an ammeter in series with your battery and measure it once started. Unless you have a current clamp handy...

You may be surprised how little it all draws (since all you have a re ECU, dash, coils ?)

Engine on , not running. 0.72 amps

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Engine running, 5.55 amps. Revving to a few thousand doesn't seem to cause an increase in current load.

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So, technically speaking, 6A should do it...

Connected 4 indicator lamps in series to Load test the LiFePo battery, results as follows
2 minutes in....... Draw = 95 watts.      Amps = 7.27 amps.     13.0 volts
30 minutes in ....             90.5 watts.                7.23 amps.     12.51 volts
( remember the draw on the battery in the bike with no alternator is only 5.6 amps, testing with a higher load so as to have a bit of a reserve buffer )
Put battery straight back in bike, touched start button, success , started up normally , heaps of grunt left in it. Track sessions are only 15mins max plus a 2 minute warning/waiting time before going out. So I have a winner
This is only a size 12, the 14 has the same size case so I'll get 2 of those to swap out. Between sessions, 45 mins apart, one will be charging

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Weiner!

Like Mark says. and wot Pete says about dinner of the chook!

Remote starter wiring

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Ron, just in case, might be worth wiring an emergency start circuit in case you stall it on the circuit somewhere