small fan

[seanbo]

i'm making an electric supercharger for a petrol chainsaw. i need to find a fan capable of the job. it must run at 24v, increase air pressure by 10-15psi, it doesn't need to move a great volume (normal intake is only about 1.25 litres per minute; less than 1/20th cfm). it does need to be small - a few inches in each direction only.

any ideas?

 

[cbarn24050]

Hi, a fan won't get you that kind of pressure, a turbine might but it would be cheaper to buy a bigger saw.

 

[seanbo]

i've got a husqvarna 3120xp - i don't think there is a bigger chainsaw (actually i know of a bigger american one, but it's an egrigate chainsaw, and really heavy). besides, i'm not actually using it as a chainsaw, i'm using it for an rc tank.

what uses a 24v turbine? model aircraft perhaps?

 

[stevenal]

Would this do it?

http://www.speakeasy.org/~rori/UltimateChainsaw.asf

 

[cbarn24050]

Hi. your flow rate doesn't look right either.

 

[seanbo]

that was pretty cool, but as you can see from

http://www.madsens1.com/graphics/ceder4.jpg

, that blade was still put to shame by this one in general production. that's the 3120xp in the picture (but i don't have a blade).

i was tinking about chopping up a portable vacuum cleaner for its motor and cantrifugal turbine. what are people's thoughts? does anybody know of a 24v model?

 

[seanbo]

cbarn - i didn't see your post until after i last posted

i know my flow rate doesn't seem right. my motor uses 1.25 litres of petrol in about 15 minutes. can somebody check my sums??

1.25 litres / 15 mins = 833 ml/min

883 ml*fuel x 14.7 = 1.225 litres*air

1.225 litres/m = 0.04325475 cfm

???

 

[cbarn24050]

Wow thats a lot of petrol, my car only uses that at 40 mph.

 

[seanbo]

but how much air does it use?

 

[nbucska]

Seanbo:
Your arithmetics is incorrect:
1.25 l /15 min = 83.33 ml assume 1g.ml (well, less but close)

I assume from your posting that the fuel to air weight ratio is 1 : 14.7. The sp.weight of air is 1.23kg/m3

83. * 14.7 = 1220 g air = .99 m3 ---> 1m3= 35.3 cf/min


<nbucska@pcperipherals.com>

 

[seanbo]

well that seems much more sensible nbucska, thanks. i think it'd be a little less, becuase the engine will only be about 80% efficient - but now i have an idea of how much air i need to move.

anybody got any good ideas for a fan/turbine suitable? it should probably move about 50cfm.