Demon Blower

[ruzzie]

I am using Inventor to model the demon V8 blower so I can machine it using Inventor HSM on my CNC, but I have come noticed when I put the rotors into my cad model I notice that there is around .43mm (.017”) clearance between the lobe.
I haven’t seen a working version of the blower and was wondering if it works efficiently with that much clearance.

 

[Vixen]

What are the clearances when the lobes are rotated by a further 30 degrees and full meshed?

Mike

 

[mayhugh1]

Ruzzie,
I can't really answer your original question about what's rneeded to produce any actual boost, but you may want to give some thought to the amount of backlash that you are going to end up with for the gears that you make (or buy) to drive the rotors. When the engine speed is suddenly changed, any backlash is going reduce the distance between the tips of the rotors, and you might find that this ends up being the major limitation on how close together you can place them - Terry

 

[ruzzie]

The clearance when they are meshed is around .1mm (.004") it just at that point the clearance opens ups.
I don't think getting the backlash better than .4mm will be a issue.

 

[UnkleFuzzy]

In a real life blower, the lobe would not have that sharp edge at that point but would have a smooth transition between the concave and convex curves.

Here is an overhaul manual for a full sized blower. The tolerances can probably be extrapolated to the scale you need.....
http://www.gardnerdenverproducts.co.../370/c941af13-b64e-4212-aa95-4a50fdfb11f5.pdf

 

[Vixen]

Your illustration of the lobes, fully engaged, shows there is only a 0.1mm (0.004") separation between and surrounding the tip of the rotor lobes . Any backlash in the gears greater than 0.1mm (0.004") will cause metal to metal contact between the two lobes. It is essential to minimize and measure the extent of the gear backlash before you can set the clearance dimensions of the rotor lobes.

Mike

 

[Nick Hulme]

Is the blower designed to run dry or wet?
If it's wet then the oil film will make a difference.
Are the rotors lapped in using a jig or are they machined to assembly size?
Can you use an anti-backlash gear on one rotor?

- Nick