Thread: Let's see what we can do.....

Originally Posted by Cal

We all know the specs that companies put on these things are exaggerated, supposedly 3hp with a 10amp plug!

Where's the problem with that?

Good price considering. It's interesting in that these various units look the same on the outside but are configured differently. If you look at the pictures I posted of mine you will note that the motor is rated @ 15A 240V and has a 15A plug and drives a bigger impeller. It would be interesting to see current consumption with the intake open on this unit. I'm wondering how the fan blades are shaped in a 12" impeller, could be one of the reasons for vastly differing noise levels between these units with different size impellers ranging from 12" to 14".

A smaller lower mass impeller could be how they get away with a 10A plug, startup current would still be relatively high though, are you sure someone hasn't just swapped the plug over for a 10A?

EDIT Looking at the pic it looks like a molded plug, either the lead was replaced or it's OEM and a light aggressive blade on a 12" is getting close to 3HP but with some extra noise to go with it, then we get into the area of fan curves. I guess as usual run one extraction point at a time, 150mm ducting and open up the machines ports. Look forward to see how it goes.

After seeing the post on your machine I was hoping this would have a 14" impeller MandJ, but it wasn't the case. I don't have any way of measuring the startup amp draw. May have to buy an ameter.

As for the plug, when I got it home I realised that the previous owner had bypassed the no volt switch. Opened up the box and so was the case. That is all better now. It maybe the case that the whole lead was replaced but I doubt it. You're suggestion about the impeller may be correct.

Are you planning on redesigning yours without the "y" piece? I was thinking if this only has a 12" impeller, would one bag be enough? With no means to measure air volume it is a bit of an unknown.

I think I'm starting to answer my own questions in my head, buy the tools to do the job.

Originally Posted by elanjacobs

Where's the problem with that?

The problem is, it's not going to be a true 3hp motor (which I already knew) drops the speed of the impeller down and also the size. It is never going to draw the volume of air that the manufacturer claims thus making the less knowledgeable believe that they are protecting their health by just banging a 4" or 6" hose on it and jobs done. It could almost be a case for a class action against all of the distributors and manufacturers of these units. It is people's health there dealing with.

Good question by the way [emoji1]

240 volts 9.6 amps best part of 2,300watts @ 750W per 1HP adds up to close to 3Hp.

Cheers Barry

Volume of air quoted as 2200 cfm would be as tested, no restrictions.

Only having one bag would increase the restrictions as opposed to two bags.

Cheers Barry

Originally Posted by mannum3

240 volts 9.6 amps best part of 2,300watts @ 750W per 1HP adds up to close to 3Hp.

Cheers Barry

Thanks for the correction Barry! Without an ameter, I am unable to verify that this unit is the claimed 3hp or 2200watt as stated on the sticker or motor. It may well be?

Why won't it be a 3HP motor?

240V x 9.6 A = 2304W = 3.1HP

OK, that's input power and output power will be slightly less to take motor efficiency into account.

The numbers on the sides of motors are nominal anyway. I have measured the output HP of several dozen motors - including cheap ones on DCs and none have been below spec
The 10A plug means nothing.

The problem (if there is one) is not the motor but the small impeller. size as this will affect the impeller curve.
But the only way you will slow down the speed or any motor is to put a too high a load on it but a 12" standard impeller is actually not too high a load on a 3HP motor so it should still spin at full RPM
To slow down a 3HP motor you would have to put a larger impeller on it.

I reckon that DC as is will serve a 6x4 shed reasonably well.

Recommendations
1) The only thing I would do to that DC initially is install a reverse Bell mouth hood on the inlet

2) Definitely leave the 2 bags on as this halves the filter resistance and it will take twice as long to clog as a single bag.

3) put the DC outside the shed

4) 6" ducting all the way to machines

5) Spend as much (or more) effort attending to machine ports and breathability.

6) Bell mouth hood on the sander like this
BSandernew.jpg

7) Small thicknessers are a PIT to fit 6" ducting to and will probably required a new machine port to be built - post some photos of what's on there now.

8) TS and other tools/machines look for ideas on this forum

Ok, my electrical knowledge is iffy! My father would not be proud of me (sparky by trade)

Thanks Bob, yes I am planning to do the bell mouth on the dc. Will do some measuring of the impeller, noticed that the fins internal diameter is smaller than the 6" inlet. Not sure if this will effect the radius on the bell mouth? I will attempt to replicate your mandrel on the lathe or make the bell mouth out of mdf. If I run into trouble does your offer of making some up still stand?

Will leave the twin bags as you and Barry have suggested.

Will be placing the DC outside in its own enclosure.

Will take some pics of the thicknesser, I will have to redesign the whole plastic exit duct though. That's ok.

This will be fun!

Originally Posted by Cal

Thanks Bob, yes I am planning to do the bell mouth on the dc. Will do some measuring of the impeller, noticed that the fins internal diameter is smaller than the 6" inlet. Not sure if this will effect the radius on the bell mouth?

If you remove the current inlet ports from the impeller and make a completely new one with the BMH attached you can always convert it back.

I will attempt to replicate your mandrel on the lathe or make the bell mouth out of mdf. If I run into trouble does your offer of making some up still stand?

Yep I still make them from time to time - PM me rather than discuss on the forum.

Yes was planning on making a whole new face and not wrecking the original one. Thanks, will pm you if needed.


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Originally Posted by Cal

Are you planning on redesigning yours without the "y" piece? I was thinking if this only has a 12" impeller, would one bag be enough? With no means to measure air volume it is a bit of an unknown.

The port and Y piece area is slightly larger than equivalent 150mm round on mine. I could not detect any real change in Open port static pressure or current with the Y removed - there is the slightest change between filter bags on and off - However I'll point this out again - I have FOUR (4) BIG filter bags - no plastic bottoms.

NOTE: If I make a small pen on the lathe - I can see a (slight) change in the Manometer from the effects of dust in the bags from that small amount of turning and sanding.

IMHO I don't think it's worth the effort of removing the Y piece - for almost no gain - unless you plan to change the orientation of the motor intake for ducting reasons.

I had NO need to line my fiber cement cabinet to get noise levels down - you may have to do that with a 12" fan moving a similar volume of air though. Apart from that it should leave a 2HP in it's dust so well worth the effort - and as others have said, absolutely leave ALL the bags on if possible as dirty bags are a flow killer and more surface area makes a big difference.

MandJ, thanks. Good to know. Mine has cloth bags along with the felt filters also. I will stick with everyone's suggestions about leaving it as is. As I have no measuring devices at the moment i have no way of knowing if I am improving flow or making things worse anyway.

The main issue I have is where the dusty will be enclosed, as I only have a metre behind the shed. The ducting is going to have a 90 degree bend as soon as it enters the shed. I can't see a way around this at the moment. I would have liked the duct to enter straight in and at the most have a 45 degree bend or less. I have a large shelf unit that will need to be moved and a sink that can't be moved from the corner of the shed where the duct will enter. I think I will need to empty the shed out (big job) to see how or if I can get around the problem (if it is one?)

As for the enclosure, still trying to work out what to make it out of that will be cost effective and reduce the noise level and I don't have much space to play with.


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Originally Posted by Cal

MandJ, thanks. Good to know. Mine has cloth bags along with the felt filters also. I will stick with everyone's suggestions about leaving it as is. As I have no measuring devices at the moment i have no way of knowing if I am improving flow or making things worse anyway.

The main issue I have is where the dusty will be enclosed, as I only have a metre behind the shed. The ducting is going to have a 90 degree bend as soon as it enters the shed. I can't see a way around this at the moment. I would have liked the duct to enter straight in and at the most have a 45 degree bend or less.

Get your self a large radius DWV bend. Its not sold as a "Large radius bend" It's a Male-female DVW bend shown in this thread
Air flow calibration measurements

It that thread I show a graph that shows that bend only loses 1% of the flow and is equal to a single 45º bend so it should work for you just fine.

As for the enclosure, still trying to work out what to make it out of that will be cost effective and reduce the noise level and I don't have much space to play with.

OK - looking at your setup it would be tempting to just string a roof between the shed and the fence and build a wooden shell under that to house the DC and stuff the gap between the shed and the fence with acoustic rock wool, but then how do you get to the DC to empty the bags. What about cutting a double doorway in the side of the workshop and accessing it from there. You could store gear or a mobile bench in front of the door as you won't need to access it very often. You just couldn't put a permanent cupboard or bench there.