Supercharger

[DaveMcLain]

The problem that I see is that the blower is a 92 series blower, not a 71. The 71 series for whatever reason has become the standard for aftermarket blower hardware. I've been thinking that I don't think it would be very tough to make an adapter hub for the electric motor shaft that can accept a 6 bolt gilmer belt style pulley, either the 8mm or 1/2 inch pitch style would work ok. Then you could use a normal style blower drive on the super charger and this would allow you to have an incredible amount of choice when it comes to driving the blower at various speeds. You could vary the drive ratio by changing the pulleys to get yourself in the ballpark capacity wise.

[Tony]

That would be nice, but also expensive, and a fair bit of work and trouble, unless you already have most of the parts on hand.

A direct motor/blower coupling would be far simpler. Just a normal commercial shaft coupler would work fine.

One flange slips straight onto the motor, secured with a keyway and set screw in the usual way. The other flange can be suitably machined to pilot direct onto the blower drive gear, and be secured with the six original gear securing bolts. An oil seal in the original blower front plate will finish the job. That would be a very compact and simple solution.

A drive pulley will require a custom drive snout with an additional support bearing to handle the radial belt loads.

I believe we have established that this blower is probably going to have in the region of 700 CFM flow capacity when driven directly by a 60Hz four pole induction motor. There is probably no real need for a radical step up, or step down in Rpm.

A toothed belt is going to add additional noise, and will require a guard and some means of adjusting belt tension. Direct coupling only usually needs some shims, and once it is aligned, it will never move. The rubber in the coupling will be quite forgiving.

Over twenty years ago, I direct coupled my homemade 7.5Hp reciprocating air compressor with great success, and the drive coupling has never been touched. The multiple vee belt drive of my 10Hp belt driven air flow bench blower has been a constant nuisance with slip and belt stretch.

Drive belts are a curse, and if they can be eliminated, so much the better. A variable frequency drive can step up motor speed as well as reduce it by running the motor at higher than normal mains frequency. There is no loss of horsepower doing it that way either.

MY next flow bench blower will be another large centrifugal direct coupled to a 15Hp two pole induction motor. That motor will be driven at up to 6,000Rpm at around 110Hz maximum. No troublesome belts required, the blower rotor sits right on the end of the motor shaft, very compact, and the original motor bearings are already suitably rated.

I only mention this to illustrate that these days, doing it with electronics can sometimes be a more practical and viable alternative to using drive belts to match motor Rpm to load Rpm.

[2seater]

I do see advantages to an inline drive setup, as it is presently constructed it has no provision for a radial load, and that would not be a problem if inline. The downside would be the length of the entire setup with a motor inline. Even stripped down the blower is about two feet long. Folding or stacking the components would be more compact but more complex. Much to think about

[riga team]

HAI ! QUESTION To Tony : ON HOW MANY THIS COMPREX CAN be suitable TO SUCK ?
ON HOW MANY CFM CAN GIVE OUT ? Anatolij http://www.directautomotiveproducts.com ... class.html

[viper6383]

I am looking to build my bench with 240V small vacuum motors. They are 4.2A at 240V. I plan to use 14 of them. The specs per motor are 62in H2O sealed and 113 cfm open. I really have no idea what 14 will do but I am expecting 113*14 cfm not considering restriction and I have no idea on flow vs pressure.

The draw on this is 60A. That will also be one very loud rig! I am asking because you guys are refering to using a roots charger with only a 7.5HP motor that might do better than mine and much quieter. Is there some serious loss with these little motors I have?

I did build my own rotary phase converter for our CNC mill so I can support 7.5HP but might look to use the air bypass method rather than the VFD just because of costs.

So does anyone think I need to drop the use of 14 small motors and look for a roots charger or what? I would think the reversal of the three phase motor for exhaust testing would make life much easier anyway but this think will gain about 100lbs at least over my original design. Those small motors are easy to speed control with a rehostat though.

Brandon

[2seater]

I am using six of the cheap single stage Surplus Center vacuum motors now. Using a 2.68" orifice plate Bruce made for me, I max out @ 528 cfm @ 29.75" of H2O. The performance is satisfactory for my needs, although more is always better, LOL. Two reasons for investigating the roots blower, first, the blower was free, the second was heat buildup. In the suck mode, heat isn't a problem but I do a lot of blow testing and the heat requires a constant correction to the flow reading using simple water manometers. I am making the assumption that the heat buildup will be less of an issue with the big blower, or at least more constant. I suppose there is actually one other reason and that would be wet flow testing should also be possible. I finally stripped the blower of the extra parts and cleaned it up. It is surprising how little force is required to spin it over, but of course there is no resistance from pressure buildup.

[Tony]

Brandon,

I think just about everyone here started out using multiple vacuum cleaner motors for their first airflow bench project. It is a simple, low cost, and easy to understand way to get started, but it also has some disadvantages too.

While those motors may be able to easily pull 62 inches at zero flow, the pressure will drop off very quickly at even low flow numbers. 113 CFM open flow is irrelevant, because the motors will never see anything lower than the required test pressure.

Don't assume that you will be able to reach anything like 31 inches at half of 113 CFM either. That is the first problem. Vacuum motors can reach impressive pressures with completely blocked flow, and equally impressive open flow CFM. But they quite often fall flat on their face at mid flow and mid pressure. There can be a big difference between individual types of differently sourced motors.

That may still not be a problem if you have the electrical power available to support enough motors. Although tolerating the heat and noise for hours on end will be something else again.

The next step up is to use a large single blower, either some type of tired old supercharger, or a recycled junk yard industrial high pressure blower of some type. You can get a lot more air for a lot less electrical power, and it will be much more silent, and far easier to control. Significantly increased size and cost is the only real disadvantage to a big single blower.

[viper6383]

Yeah, I pretty much figured we were going to see some major efficiency problems with these motors and I am still trying to figure out both how to adapt our pressure transducers to the bench to all proper measurements, and how to reverse flow with my design. I am trying to stay compact. I realize that my flow numbers would not be linear from the motor specs but I don;t have anything else to go on right now.

The one major problem I am looking at is sealing off individual motors that are not used. I am just having second thoughts about this design. Can you tell me what the pro benches like Superflow use for there vac needs? I am thinking a centrifugal blower with a 3ph motor might work best for my needs. I really want about 800-1000 cfm at 28in if that helps. Thanks

Brandon

[Tony]

If staying compact is really an issue, and if you are serious about requiring 1,000 CFM, then the answer is a three phase motor of around 10 to 15 hp, and a centrifugal supercharger. The whole thing could be driven from a variable frequency drive, and as a pressure/vacuum source it would be excellent in every respect. Brand new it would be horribly expensive, but a bit of judicious scrounging here and there could do wonders.

Google "Vortron.com" to get the general idea about this and see what is possible, but a homemade version would work just as well.

An industrial air blower would be cheaper, but a lot larger, at two to three feet in diameter. Though it would still require around the same drive horsepower.

As a matter of interest 1,000 CFM at 28 inches is 4.37 hp if the blower was an impossible 100% efficient. Twenty five, to forty five percent is more realistic for a real blower.

The commercial airflow benches all use vacuum cleaner type motors, to keep down the size and cost (to them!).

[viper6383]

Well since my bench is pretty much fabbed at this point, I am thinking I should finish this one and plan for another later. Got any ideas what numbers I can get with my 14 motor setup? The reason for my big air numbers is I need to test carb flow and intake flow. We do CNC engine work and need to test intake parts.

I am just wondering how the Commercial benches like Superflow work in dialing in the flow. My design calls for switching of the motors with x2 or x1 configurations and one variable motor with a rehostat. If I don't have a motor running, it will have loss through it thus the need for a check valve of sort. Also, the exhaust testing just makes this even more of a pain to figure out.

Do you have some layouts of the commercial benches or know what they do?

[gofaster]

This is a thread about check valves.



So is this:




I was at my desk waiting for an "important" phone call, and was nosing around on the forum while waiting. It is a good way to get some value out of time that is otherwise squandered. A quick search of "check" and "valve", "All open forums", "from the beginning" yielded this info. Two very informative threads initiated by Mouse and 86Rocco.
Hope it helps.
This forum has a great search engine. I had to learn to remember to click on "from the beginning" to get the best results.

[2seater]

If I can achieve a little over 500 cfm @ 28" (or 250cfm @ 56")with six cheap motors, fourteen of them "should" get you what you are looking for, plus it will heat the shop in the dead of winter IMHO, a seperate motor box works very well, no matter what style test fixture/cabinet is used. mount it on wheels, and simply turn it around for suck or blow.

[RRBD]

Hey Fella's long time no talk.
Recently I have been under the assumption that 1 Hp Electric is equal to 2Hp Gas.
I think I read it somewhere in my little black pocket reference. Up to that point I thought 1Hp is 1Hp but have actually heard it elsewhere as well.
I have a SC from a 3.8l GM and a 2hp 3-phase motor I have wanted to do some testing with
but havent had the time. He!!, I havent even powered up my FP1 yet and bet its over a year since I bought it. Life seems to get in the way alot.

Scott