Hotrodding a 1980 Shopsmith 3300

[Bruce Seidner]

This fella had been active gathering dust until it was made redundant with a central system. Now it's just gathering dust. It's incredibly well built with a thick poly body and sturdy frame. It's just way underpowered.

I was noticing those industrial 55 gallon twin motor shop vacs that sell for $1k and wondered what they were about. Looking at schematics I see that someone had the clever idea of mounting a couple $60 3 stage vacuum motors on a drum lid and charging a whole lot.

I'm in the process of replacing the 3300's felt bag with a twin vacuum motor box. I've taken the blower assembly out of the 3300's carcass and will use that space for the separator. I have a 30 gallon car wash soap barrel that is going to be mounted below. It's pretty thick walled but may require external ribs for support against  the 130" H2O lift of the motors. They are rated 105cfm so it will ostensibly pull 210cfm. To my knowledge static lift is not additive and lift of two is the same spas the lift of one.

I welcome advise but I have a question about the size of the intake between the motor box head unit and the separator. Typically this is set by the size of the blower. Shop vacs typically 2.5", Harbor Freight collectors 4", etc. I plan on using this mostly for sanding tools and routers so my tool inlet will always be 1.5" .  I don't know and can't find information on what effect the inlet to the blower makes when the size is not related to an impeller size.

Like with most things Thien I have confidence there is a wide range of acceptable. But, because I have no idea if it would be better to use a large or a small diameter inlet to the vacuum motor box I would appreciate the support and advice of the forum.

Thank you and Happy Holidays.