Calculating pulley sizes. Assuming engine speed is as rated?

Hi guys,
I'm in the process of calculating pulley sizes and am having fun the all the formulas.
My Lister B is rated at 650 rpm. Do I make my calculations based upon this or do I need to know what speed my engine is rotating at in "real life."
It is to power a generator so rpm is fairly crucial.

Additionally, to complicate matters the generator is a metric shaft as far as I can tell. 35mm
Where can I source pulleys for this, does anyone know?

(Assuming I have a 6inch pulley (1.5inch bore.) on my 650 rpm engine I will need a 2.6 inch pulley (35mm bore) on my generator. Where would I get one?

If I'm off in the wrong direction with all of this please nudge me back on track.   

I would se what speed your engine is running at first, 650rpm can be a tad fast for rally purposes. My A used to run at around 500rpm and that sounded about right. I had a 8" pulley on the engine and a 3" pulley on the generator to achieve close to 1500rpm. As for a pulley you will probably need to have one machined out to 35mm, i'm sure if you put a wanted ad on here or keep your eye on ebay something suitable will turn up.

Ok. Thanks. That all makes sense.
How best to calculate RPM?
There's a laser device for the purpose on eBay for around a tenner. Is that the way to go?

I guess the best way to approach this is to get pulleys that are as close as possible and then make the fine adjustments with the governor mechanism. Correct?

I have a pillar drill and good clamps and vices. Could I machine out a pulley to 35mm at home with any ease does anyone think?

I have never used a laser tacho, I have an analogue version (probably 50+ years old). Yes once you have your engine running at a speed you are happy with i'd do the pulley calculations from that. You could have a go at machining a pulley but it would need to be machined central (you don't want a pulley @1500rpm wobbling) Better off having it done properly at a local engineering company, it shouldn't cost too much.

Handmade Matt wrote:Ok. Thanks. That all makes sense.
How best to calculate RPM?
There's a laser device for the purpose on eBay for around a tenner. Is that the way to go?

I guess the best way to approach this is to get pulleys that are as close as possible and then make the fine adjustments with the governor mechanism. Correct?

I have a pillar drill and good clamps and vices. Could I machine out a pulley to 35mm at home with any ease does anyone think?

Yep, for the alternator you'll need to see the rpm of the engine before calculating pulleys, this will give a start point you can then tweek the engine speed while measuring the rpm of the alternator. The Pulley center for the crank should be 1.5", you will have problems getting this right with a pillar drill and once the damage is done the pulley will be scrap. you would be best off buying a pulley with a 1.5" center.
You may also find this useful
http://www.csgnetwork.com/pulleybeltcalc.html
Did you get the email with the PDF for the AC1ZS and see the info I found?

Pulley speed...

http://www.blocklayer.com/pulley-belt.aspx

Pulley...

http://www.bearingboys.co.uk/V___Wedge_Pulleys-1038-c

Simples.  

i would use SPA section if i was you the more belts the better the drive you will put out ...

matt

Thanks again everyone.

blackvanman wrote:The Pulley center for the crank should be 1.5", you will have problems getting this right with a pillar drill and once the damage is done the pulley will  be scrap. you would be best off buying a pulley with a 1.5" center.

The engine crank shaft is 1.5" and I'm happy to buy this as a stock pulley.
It's the generator shaft that is 35mm. I will try to find a local chap who can machine it for me.

I don't really know what spa spb spc spz means. If anyone can point me towards some reading material that would be great.

(Am I OK to base all my pulley sizes on the RPM measured without a load?)

Incidentally, a friend has said that he has an old belt driven circular saw table in a shed in some woods that he has. He said I could have it for a bit of negotiation. I'm going to go and have a look at some point.

the spa spb spz reference is for belt cross sections....

Have a read here: http://www.speedcontrolinc.com/file/1294711695section1metricvbelts.pdf

I measured the RPM of the Lister today. At a slow tick over, firing every now and then it was running at around 430rpm. I experimented with the governor and managed to increase this to 500rpm. It fires more regularly and sounds stronger at this rate. I manually teased it to 650rpm to see it running at it rated speed and it's quite a rate for the old girl! I assume it's at this speed that the engine would theoretically output it's rated 5hp.

I'm thinking to purchase pulleys that would allow me to achieve the rated 1500rpm of my generator with the Lister running at around 500 to 550rpm. It's a 1.3kw generator so is well within the capability of the 5hp Lister without it straining. What are your thoughts?

Have looked at a taper lock pulley you buy taper lock centre to suit your shaft i e 35 mm or 13/8 imperial ? the type that uses 3allen screws to lock it to pulley and the pulley to suit your speed KRAMP UK - 01767 602 600 have these they are based Biggleswade not a lot of money

HOPE THIS HELPS

Thanks. That is helpful.