Thread: The most annoying question(s) - What should I do?

Ideally I'd probably have the whole system sitting outside to save workshop space, but either way I was planning to at least vent outside.

Does the VFD take care of running a three phase motor on common single phase house power? I thought they just did the 50 to 60Hz magic but I'm no sparky by a long shot.

In terms of speeds, I'm after whatever will do the fine dust collection as well as chips, so the usual 1000/4000 thing is the target with only one machine connected at a time. I don't think I want or need anything greater.

So let me see if I'm understanding this from what you're saying...
- A single phase 3HP/2850 RPM motor will get about 1250 CFM through 6" ducting.
- A three phase 3HP motor with VFD will get me 3600 RPM with the same 1250 CFM through 6" ducting and 1500 CFM through 8" ducting.

- Therefore to reach my 1000/4000 target I can get away with using a single phase 3HP/2850 RPM motor with 6" ducting (?)

What sized impeller is used in these values?


It's newish information so I'll have a fiddle with the static calculator and fan table some more. At the moment, with some quick and dirty calculations with and without things like a cyclone: on 6" ducting, I'm seeing 5093 FPM and 7-9" WP total loss but with 8", only 2865 FPM (but says it's OK) and between 4-7" WP total loss. So how does that also figure in with what you're saying? I can see how the 8" ducting is helping with the static pressure and motor HP factors but also don't understand why 2865 FPM is deemed OK,

And just an FYI, I have been considering making my life easier (and everyone else's by not constantly asking questions ) and seeing if I could use either a FM-300 or more likely a FM-400 blower from Timbecon ( Catalogue - Safety - Dust Extractors ) on 6" ducts like mikm did here https://www.woodworkforums.com/f200/m...blower-101128/

Howzat grab you as a solution?

Ebay is a good source for bits. I watched and waited and got 15m of flexible hose for $25 and bought a 1Hp dust extractor for it from China. The extractor didnt work all that well because it couldnt take shavings, so clogged easily and was a bitch to empty. Overcame that with a plastic drum with the dust pulled into that to cyclone first. Only problem now is for some reason fine dust gets into the extractor switch and that has to be stripped and cleaned. If I was doing it again I think I would try to have the piping standard plastic and design my space for it. Reason flex hose with wire in it is rough and very noisy.

Originally Posted by RedShirtGuy

And just an FYI, I have been considering making my life easier (and everyone else's by not constantly asking questions ) and seeing if I could use either a FM-300 or more likely a FM-400 blower from Timbecon ( Catalogue - Safety - Dust Extractors ) on 6" ducts like mikm did here https://www.woodworkforums.com/f200/m...blower-101128/

Howzat grab you as a solution?

The FM 300 only has a 5" outlet so you would have to modify the impeller housing. The FM 400 has a 6" outlet which is better.

Kewlies. I was thinking the FM-400 anyway for the 3HP. It's something to keep in mind anyway.

I'll just keep looking at things until I can either put together or buy a decent blower. With the motor tweaking info you've given me I think my next course of action is to source a suitable impeller that isn't going to cost the world to have made. If I thought finding a motor was difficult, I think this is going to be even harder. Time to hassle some vendors for spare parts me thinks

Seen these?

Smiths Industrial Fans | Products | Portable Fans | Portable 150mm & 230mm Centrifugal Fans
Cast Ally impeller, 150 mm intake and 230 mm exit.

The 2 HP 230 mm diam says it pulls 2000 cfm - it will be interesting to see what pressure these can generator. There are several of these available locally sale second hand - I might buy one for fun and have a play with it. A 3 phase one with a VFD would be an interesting.

Cheers
Bob

Ooh. Would be interesting to see how they fare. If you ever get one and do some tests on it, let us know how it rates.


Edit: I had to look it up myself, but if anyone wants to know how BobL got 2000 CFM from the details on the website, it's a conversion of the "perf L/sec" column (litres per second)
2HP 230mm diam - 950 [liter/second] = 2012.935974 [1 cubic foot/minute]

http://www.onlineconversion.com/flow_rate_volume.htm

Originally Posted by RedShirtGuy

Ooh. Would be interesting to see how they fare. If you ever get one and do some tests on it, let us know how it rates.

I went and had a look at these used fans this morning. It turns out the place was an old mushroom farm in the Perth Hills and the blowers were used for climate control of the mushroom sheds.

The owner had about a dozen fans, mostly 1440 rpm with glass fibre housing impellers and stainless or plastic impellers. The plastic impellers were conventional design and had adjustable angle blades. The stainless impellers were light gauge squirrel cage type impellers and I doubt either these or the plastic ones would stand up to much if hit by a piece of wood. These were also all only 1HP.

There were several 2HP steel housing with impellers made with thick (10 mm?) ally blades that could probably handle a piece of but the housing were rusted beyond resurrection. The owner said they had a lot of trouble with the bearings on these unit.

So, all in all an unsuccessful trip into the Perth Hills, although not completely wasted because I managed to pick up a couple of trays of tree ripened fruit - pears, apricots and peaches.

Aww, now I'm jealous about your fruit too

For what it's worth...I've just gone a bought myself an FM-400 and plan to build a Bill Pentz cyclone to go with it next year.

There are a couple of reasons (not related to performance)...
- I spent a morning hassling every single local engineer about making an impeller but no-one was able to make a BALANCED one. [Your favourite deity] knows how much it was going to cost to get one made by a professional fan company (I had a couple in mind) but I doubt I was going to get much change out of $200-300 at least.

- And the big one...while talking with BobL about a 5hp 3phase motor I'd been dribbling over on eBay (older model, but brand new and it went for $39.70) and various VFDs/VSDs and their costs, I realised that I am never going to have at my current location the power requirements to be able to run the blasted thing.

Bugger.

So the FM-400 should do for the time being, and if/when I'm in a better location and able to go the full hog on a 5hp system I'll try to sell it off with the cyclone to recoup some of the "loss".

Still...a new toy is a new toy, and 'tis the season

Good luck RSG

Everyone appears to be hung up over the 5hp thing. The 5hp came about because in the US to drive a BP designed system took more than a nominal 3hp motor could comfortably do with any reliability and in the US there is nothing between 3 & 5hp while in Oz nothing that equals 5hp. A 3kw Australian sourced motor will drive a 15" impeller quite comfortably and the current draw is not as high as a 5hp, obviously. CV have used Leeson 5hp exclusively due to it being bullet proof and they being the only ones prepared to custom make a motor for the purpose.

Power is a function of speed, as US is 60Hz which means higher RPM 2 pole =3600 (no load) so US motors will be rated higher than here (for comparable motors given the same torque) a 5hp rated motor here should have more grunt than a US 5 hp motor


Pete

Originally Posted by pjt

Power is a function of speed, as US is 60Hz which means higher RPM 2 pole =3600 (no load) so US motors will be rated higher than here (for comparable motors given the same torque) a 5hp rated motor here should have more grunt than a US 5 hp motor


Pete

Pete, I have always been told that 2 pole motors on 60hz = 3450rpm, not so?