Thread: The Generic 2HP DC

FYI: Larger sloping manometer I made years ago, tested against a digital manometer.



Digital unit if you don't want to make one.

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Originally Posted by MandJ

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That's the one I have.

Well there you go, I should have added to my post that it's the one I have as well

Does anyone know the shaft size for the genetic 2hp DC motors? Also, do you know if shafts are generally the same size for all the genetic 2hp Motors?
I would have to dismantle a shed etc to measure mine, so hoping someone knows

Cheers.

All the shafts I have seen for the generic 2HP DC motors have the same but I cannot say for sure what that is.

Standard shaft size for a 2HP induction motors (based on a 90S frame) motors is 24mm so if you look for that on the motor name plate that will be a useful cue.

Some 2HP motors (e.g. on bandsaws) do have their 24mm shafts turned down to 19 mm but that should be fair obvious by looking at the top of the impeller.

Thanks Bob. I may be able to get my hands on a 3hp motor cheap. It has a 25mm shaft and I was thinking I may be able to replace the 2hp DC motor with it.

Originally Posted by Lappa

Thanks Bob. I may be able to get my hands on a 3hp motor cheap. It has a 25mm shaft and I was thinking I may be able to replace the 2hp DC motor with it.

3HP motors usually have 24 or 28 mm shafts.

I assume you realise that a 3HP motor won't make any difference unless a larger impeller and impeller housing are used? Both the 2 and 3HP will spin at the same speed at 50Hz. If you install a 3P motor and a vid you can spin the existing impeller faster and get more flow.

Originally Posted by BobL

. If you install a 3P motor and a vid you can spin the existing impeller faster and get more flow.

That’s the idea. It definately has a 25mm shaft.

Originally Posted by Lappa

That’s the idea. It definately has a 25mm shaft.

If the impeller has a 24mm bore that's going to be tricky.
It cannot be bored out with just a drill bit as bits are too inaccurate so the impeller will need to be mounted on a lathe and the bored using a boring jig..
Spinning a 12" impeller on a lathe is a job for a large lathe and someone that knows what they are doing.

Lathe work is not a problem and neither is balancing. Maybe it would be easier to turn the armature shaft down if it hadn’t been hardened.

Originally Posted by BobL

3HP motors usually have 24 or 28 mm shafts.

I assume you realise that a 3HP motor won't make any difference unless a larger impeller and impeller housing are used? Both the 2 and 3HP will spin at the same speed at 50Hz. If you install a 3P motor and a vid you can spin the existing impeller faster and get more flow.

Don't forget that increasing rpm to get more flow is less efficient than increasing impeller size at the same rpm. However it also depends on the amount of resistance in your ducting system as you'll get a significantly higher max static pressure increasing rpm. But i would guess even a 2hp "modified dusty" is unlikely to produce 2hp at 60hz in a typical, connected system including a machine. Has anyone measured the amp draw of a modified 2hp when conncted to ductwork and a machine? I recall my 2hp unit only producing about 1.3hp (can't remember exactly off the top of my head but remember it was low) wide open with no ductwork and a new pleated filter.

I fabricated this 'Jonno' style adaptor out of plywood to modify a generic Carbatec 2hp DC and connect the bag ring directly to the impeller output.

In the end I've decided on a totally different way to do the mod so don't need this part any more.

If anybody reading this thread would like it for your own mod, you can have it for the cost of postage - just PM me.

Originally Posted by Ian Dobson

I fabricated this 'Jonno' style adaptor out of plywood to modify a generic Carbatec 2hp DC and connect the bag ring directly to the impeller output.

In the end I've decided on a totally different way to do the mod so don't need this part any more.

If anybody reading this thread would like it for your own mod, you can have it for the cost of postage - just PM me.

Hi Ian,

Any chance of telling us how you intend to do the mod ?

I'm starting to mod the intake for my Carbatec 2hp dusty. I have a 16mm melamine faced MDF disc to replace the metal impeller cover and a 25mm mdf backing plate to make a total of 41mm with which to form the reverse BMH. These both have a hole machined to the id of the 6 inch DWV pipe. I then have a further 2 25mm mdf plates with holes machined to the od of the pipe so the pipe will slip in and fit to the reverse BMH.
I have come to a standstill with regard to forming the reverse BMH. I don't have a lathe, or access to one, and a 38mm roundover bit is prohibitively expensive for what will possibly be a one time use.
Has anyone got any other suggestions, or even a router bit that I could borrow/hire?