quandary: which type of flow bench to build?

[ron thorne]

I have researched the pts orifice and pitot style systems available. I will be testing at relatively low cfm (approx. 200 cfm), max lift .400", low cost (but want digital manometers), and would like to use my current shop vac, if possible. I don't really care about the actual cfm numbers, only repeatability. I make very small changes to the port(and manifold) The questions:
1. Why is the pts dm so much cheaper than the others ($325.00 compared to $600- $800)
2. Does it (the pts dm)automatically calculate cfm to 28" as actual depression diminishes similar to audies and flow performance systems (i.e. is it a digital manometer and a depression calculator)?
3. Can I use a shop vac (or 2) with your system?
4. Does depression(different orifice size) have to be changed during a normal flow test to .400"? If so, how is that accomplished?
5. Does barometric pressure, humidity, and temperature affect flow rate and need to be accounted for in testing with the pts system?
Awesome web site. Keep up the good work. Thanks, Ron.

[Brucepts]

1) Because I make less profit My DM gives you 3 sensors standard, most others upcharge you.

2) It can do static pressure conversion on-the-fly but it's best to test at a set depression and not convert. Lots to read about that theory here on the forum.

3) You could use a shopvac but you would be testing at some very low depression. See 2 above it's not a good thing to do conversion in my opinion. Take the money you are saving on the digital manometer and spend it on real motors in a PTS flowbench.

4) For the range you are working with on a PTS flowbench you would not have to change ranges you can work within a 0-450 range. Some are working with a 0-600cfm range but numbers are slow to respond at sub 50cfm

5) no need to worry about baro and temp on my orifice style flowbench, same air going through your part goes through the measuring orifice so temp and baro are not effected.

6) I know there was no 6 but had to add; I support my product

[ron thorne]

Thanks for reply, Bruce.

More questions.

You recommend to test at a set depression. My cheapy flow bench (which taught me a lot but was very tedious to operate) I built last year was patterned after an old CarCraft magazine article from the 70's using a toilet plunger and rubber stopper for depression adjustment. flow @.100 lift, adjust depression, flow .200, adjust depression with plunger/stopper, etc. (1)With your pts plans, do I have to adjust depression at each lift point? (2) If so, what type of valving in your bench does that? (3)What is the purpose of your orifice plates ( qualify the cfm numbers?)? If this is proprietary knowledge included with your plans, I apologize for asking. Trying to understand how a orifice type flow bench works. Thanks, Ron.

[Brucepts]

Depression is set with a motor control that speeds up or slows down the motors manually with a control pot. Various types of controls can be used from a simple router control to the solid state relay/phase angle control I supply. Less wear and tear on your motors as they are not being throttled while at full speed. It all comes down to how much testing you plan to do and your budget.

Each lift point requires an adjustment back to your test depression, testing at the same depression each time gives you a standard to work to. Comparison testing does exactly that compares but what happens at say 28" might not be what happens at 10" or 5" with your cfm if you are converting back to say 28"

The orifice style flowbench measures the differential pressure across the orifice plate. Take a look at the Flowbench 101 post on the forum. Plates are discussed on the forum so nothing is proprietary, I use a different spreadsheet to do my math from the one Rocco has posted here for everyone to use for calculations.

I'm not one for spending other people's money so I do not try and up-sell anything. I do not feel someone would need, my parts are priced fairly so most anyone can afford them and I can say I have alot of satisfied customers! Pricing on my digital manometers represent an agreement I have with a few forum members who helped design this product, I was to offer it at a price point so anyone could afford them and I make a profit. There are pictures here on the forum showing the inside of my DM compared to the more expensive product on the market and they speak for themselves on which is a better looking product

I think sometimes my lower price has people shying away thinking it's a lesser product due to cost??? I will say that the parts I use inside the box are not of cheap quality, I use 1% to 5% components as apposed to 10-15% quality which would still work.

[1960FL]

Ron, Welocme aboard.

I will be testing at relatively low cfm (approx. 200 cfm), max lift .400",

If this is in fact the case you could build a PTS bench with 4 motors in it and plug the other 4 and have plenty of power to test at 28" and maybe more.

Rick

[ron thorne]

Thanks again. I understand now and can make a decision. Ron.

[ron thorne]

Thanks for the input, Rick. Bruce what is the cost of the software for the DM? Also price of the motor control you offer? Cheap HF router controller could only be used for 1 or 2 motors, right? Lots of info on here to digest. Thanks, Ron.

[ron thorne]

Found the price of your motor control ($245.00).

[Tony]

Thanks for the input, Rick. Bruce what is the cost of the software for the DM? Also price of the motor control you offer? Cheap HF router controller could only be used for 1 or 2 motors, right? Lots of info on here to digest. Thanks, Ron.

Simplest and lowest cost way get started would be to control the speed of just two motors with a low cost HF router controller, and switch the other motors on or off individually with switches as required. This does require simple non return valves to be fitted to the unpowered motors.
This is an entirely practical system that many Forum members are using.

The next step up from that would be to control all the motors simultaneously with a single high power phase control module. These can control up to 100 Amps or more. You get a ten turn knob to directly control motor speed from zero to flat out, eliminating the need for the switches and non return valves.

Third upgrade would be to hook up the input of the high power phase control module to the fully automatic closed loop PID test pressure controller (available from Bruce). This is an absolute delight to use, and if you do a lot of testing, you will never go back to manually adjusting test pressure.

[ron thorne]

Thanks, Tony. You guys are very patient with my questions. Ordered plans today. Scrounging for used vacuum motors. If I can find the motors cheap enough, then I may spring for an automatic depression control.