I suspect the answer to this question is a resounding no, but I thought I'd ask:
Have any detail drawings of the WH Allen motors on the ventilators ever surfaced?
I'm trying to establish a physical dimension logic - they are referred to as '30 BHP' and '15 BHP' etc depending on the vent that they are servicing, but would this translate to a variation of size in the casing?
#55518, "RE: Sirocco Motors." In response to Reply # 0
Hi Nick I don't know about resounding but no I'm not aware of any technical drawings of any aspect of the electric fans. When I drew them for my plans all aspects had to be sized based on surrounding structures and comparisons of many photos. Regards Bob Read
#55519, "RE: Sirocco Motors." In response to Reply # 1
Thanks, I thought as much. I 3D modelled and printed two different sizes based on what I cobbled together (before I purchased your plan! - probably should've done that first...) and have come to realise that there were probably a greater variety of sizes. At 1:100 it won't really matter, but at a larger scale it might come in to play.
On a side note, WH Allen archives are apparently quite comprehensive. If you can find which location they are housed in!
#55520, "RE: Sirocco Motors." In response to Reply # 2
As far as I'm aware Bob is correct that no detailed drawings of the motors have come to light. Generally speaking the size would be proportional to the horsepower, so there would be a considerable difference between the 10 b.h.p. motor for a warm air delivery fan and the 3/4 b.h.p. used for a lavatory extractor.
If you find anything in the W.H. Allen archives I'd be interested to hear of it, but I'd be very surprised if they kept engineering records to the level of detail that you're looking for.
#55521, "RE: Sirocco Motors." In response to Reply # 3
I suspect you're right - and the archive search has been unhelpful thus far. It feels like it's the sort of thing that might appear in a period catalogue, or if there was any operators manual for such a device.
#55522, "RE: Sirocco Motors." In response to Reply # 4
Hi Nick. Can I suggest that a motor of twice the power would be 1.414 times the physical size? The reasoning is that obviously putting 2 motors end to end would double the length and double the power. Likewise going to twice the diameter would double the circumference of the rotor, thus the surface area for the magnetic reaction between the rotor and the stator and so would also double the power. But as each of these offers poor proportions what would be more likely is to use 1.4x length times 1.4x diameter when one wants to get 2x power.
#55523, "RE: Sirocco Motors." In response to Reply # 5
just measured the sizes of my tin cast motors in 1/100: 20 inch sirocco fans: length 6,5 mm x 5,5 mm dia. 30/35 inch sirocco fans: length 9 mm x 8 mm dia.
My own estimations from my TTSM 1 book drawings (David Cotgreave, Bob Read), photographs, Andrews notebook, etc. copied by myself in scale 1/100: 10 inch sirocco fans, motor 0,75 BHP: length 4,5 mm x 4 mm dia. 20 inch sirocco fans, motor 2,5 BHP: length 6,5 mm x 5,5 mm dia. 30 inch sirocco fans, motor 6 BHP, some 7,5 BHP: length 8 mm x 7,5 mm dia. 35 inch sirocco fans, motor 10 BHP: length 9,5 mm x 8,5 mm dia.
As these are all estimations, I built the single 10 inch fan motor scratch, one tin cast for 20 inch fan motors and one tin cast mold size for both the 30 and 35 inch motors.
With same length to diameter proportions, I would say, the power in BHP should be about proportional to the volume or weight of the motor, that means 2 x length/dia. = 8 x power, so lets check the above estimations: 10 inch sirocco fans, motor 0,75 BHP: 42% size = length 4 mm x 3,6 mm dia. 20 inch sirocco fans, motor 2,5 BHP: 63% size = lengh 6 mm x 5,4 mm dia. 30 inch sirocco fans, motor 6 BHP: 84% size = length 8 mm x 7,2 mm dia. 35 inch sirocco fans, motor 10 BHP: 100% size = length 9,5 mm x 8,5 mm dia.
I hope, this site keeps alive in discussions, etc., so this is only my estimation on this subject.
#55526, "RE: Sirocco Motors." In response to Reply # 7
Hi Nick and Bill,
I thought about our above thoughts and some differences. There are two formulas:
Mine is: weight or volume of motor is proportional to power. For same proportions: dimension times three = proportional to power.
About Bill's thought: "The reasoning is that obviously putting 2 motors end to end would double the length and double the power." Agreed, double weight = double power.
But going twice the diameter with same length would be 4 x volume, weight and power. A motor of 1,4 x length and 1,4 x diameter = 1,4 times three = 2,744 x power. Or 2 x length and 2 x diameter = 8 x power.
With Bill's formula (dimension times two = proportional to power), a smaller motor would have a much better power to weight ratio, and I think, the power should be roughly about proportional to the weight.
I hope, this clarifies the different thoughts. It's not an exact formula, as different motor sizes could also be technically internally different, etc., etc., and I am no expert on electric motors.