View Full Version : Does this sound right?

hovercad - n/a
1-May-06, 02:49 PM
Hello All,

Just thought I would see if im on the wrong track or not.

Duct size 850mm

max revs of engine 7000.approx 50hp max

Avaliable sizes of htd 8mm pulleys decided on 26/56

This gives a ratio of 2.15 = fan speed of 3250 rpm

Tip speed of 144.6 m/s

Driving a 9 5z hub with nine blades.

Just thought I would check as them pulleys arnt cheap if you get it wrong.



darwin - n/a
1-May-06, 04:36 PM
If your planing to race would use a 28 pulley on the bottom so to keep as many teeth in contact with the belt 58 top 150m/s or 30 bot 62 top 151m/s or if you want to run the fan at 167m/s use 28 bot 52 top but only use 6 blades in 9.If it's for a cruiser thats completly different.


hovercad - n/a
1-May-06, 05:28 PM
Hello Geoff,

Not too sure at the moment.Kids cant race with the engine .Robin ec44.

The hull Fenland flyer so not suited for cruising.

Engine was a drunken ebay buy 80.lol

Ive been trying to get of the ground for about 5 yrs now so thought go ahead with the robin then if an engine suited for f3/juniors comes along at the right price would put that in the fenland and the robin into a simple cyclone hull ive got as well.


darwin - n/a
2-May-06, 06:25 PM
Hi cadfly

A rotax should rev to 6500 so just in case you get an engine without a gearbox may be go conservative on ratio to use either engine as pullies cost about 1.50 a tooth maybe more as it's along time since i had one made.

I may have a 447 for sale soon with a gearbox ratio 2.24/1


hovercad - n/a
3-May-06, 04:12 PM
Hello Geoff,

MMMM another engine.

When you know give us a shout could sell one of the kids.

Damn would still have three left.lol