My friend 'OWELLY' was thinking we might get the round the problem of having very little room in the engine bay, and not having an alternator, buy using a bike alternator.

Will it work ?

We were thinking about mounting the rotor on one of the pulleys, and fabricating a bracket to hold the stator.

What do you all think.

Saves room

very small

Low output

need for rectifier / regulator

has anyone thought of this or used this, or is it a stupid idea ?

will a small alternator (e.g. like one of the brise ones) not fit?

have a look at one from a yamaha they are a self contained discreate unit . the problem with doing as you sugest is the necesity of having very close tollerence between the rotor and the stator if you were to use the yamaha unit you could have a coupling from the crank to the alternator and it would tollerate being driven at engine speed .
best wishes
Iain

are not bike alternators fairly low output?

seems the common route is to use a small car / van unit from a daihatsu or similar.....

atb

steve

Trev,

As Steve says, Daihatsu or Bedford Rascal (and its other identical versions) have a lovely small alternator. It has a Pinto profile pulley which may or may not be of use to you.
The 2CV one is tinier still as it has a separater regulator. Unfortunately new regulators are quite expensive.

HTH,

James

Does the bike alternator give its small output at lowish revs or does it need to rev quite high? it would be awkward if it doesnt start to give reasonable outputs until (eg) 4 or 5K revs.

Bike alternator is a permanent magnet device so it's otput voltage is proportional to revs. The regulator is likely a "buck converter" that multiplies up the amps while dividing down the volts to 14V (ish).
So you'll get useful amps at whatever revs the output volts before the restifier/regulator goes over 14V - this is likely to be just under idling speed.
So you'll get a bit of juice at idle & serious amps at higher revs.
I'll have better info when I've got mine going in a few months time......
Cheers
Bob

Was just a thought.

I could most probably face it backwards in front of the engine, but was just trying to com up with alternatives. Space is tight

quote:

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Originally posted by James
Trev,

As Steve says, Daihatsu or Bedford Rascal (and its other identical versions) have a lovely small alternator. It has a Pinto profile pulley which may or may not be of use to you.
The 2CV one is tinier still as it has a separater regulator. Unfortunately new regulators are quite expensive.

HTH,

James

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I (and a few others on here) have got a denso alternator of ebay, cost me £40 but is brandnew and only 100mm diameter. Might be worth a look ?

bike alternators are fairly low output-only 20-30amps depending on types and they also rev to 12000rpm ish to may not be very suitable for car eng and yes you would need reg/rect

Low output 20 - 30 amps.

If that's the case then it would be plenty. We don't need a big alternator on a locost.

The alternator only needs to have an output that will ballance the loads. The loads on a locost are what???

Lights 55w each x 2 = 110w / Volts = amps used = aprox 10 Amps
Side Lamps 4 x 5w = approx 2 amps
Wipers Approx 8 amps
Heater blower approx 2 amps
Rad fan approx 10 amps

Total 32 amps with everything on (conservative figure)

You only need big alternators for large loads like electric windows, central locking, heated rear screens / windscreens etc etc.

Large output alternators are a waste of space and weight when not needed. Much better to get one that is about 10% more output than all your loads added up.

If you were to look at the current profile of an alternator when it is working you would see that the large outputs are only given for a very small amount of time (1 or 2 seconds) after starting. The current quickly drops off as the batter voltage comes up to 14v.

Contrary to popular belief, alternators do not fully charge a battery. They only bring it up to 14v. They never actually fully charge it.