Bench question................

[gavinator68]

If I were to use a variac for the depression control on a bench similar to the JDF bench built by blownalcohol, would I need the port that would not be used for an automatic valve. It seems to me that I could just put one hole at the bottom and run the tube to the plenum from there. Any thoughts?

Cheers,

David

[bruce]

Your thinking is correct if you use a motor control you do not need a manual/automatic bleed valve. But it would be nice to plan that into your bench so at a future time you can add automatic control if you see fit.

[gavinator68]

Very insightful Bruce......................

Thank You!

[racehead]

[color=#000000]Which way is the best for the depression control.
The motor speed control or the automatic bleed valve (PMW valve from Flow Performance)?
I do understand with the PMW valve the depression doesn

[bruce]

Well I can not personally speak for either since my current bench is mechanical control, but everything I have heard about the PMW is nothing but "GOOD". Just the idea of not even having to worry about adjusting your flow depression either manually or electrically is enough for me to go that route.

Yes you have the "cost factor" but I'm sure once you see how well it holds the depression you'd never think of doing any other way. How much testing you do also has a lot to do with the way you go to control your depression. It's the same discussion for digital/water gages, but once you go digital you'll wonder how you did it any other way.

Think about the cost factor a tad . . . years ago this was some "black art" and now people are building flowbenches at home that are more accurate than some of the commercial benches selling for $$$$'s. Most of those benches that were built were built for a serious savings. So you can spend the $$$'s on digital with all the bells and whistles as most people a few years ago never had thought of owning a flowbench till we all got together and demystified the "black art".

As for the noise factor . . . that's why they sell hearing protectors

[racehead]

[color=#000000]Bruce, like I said before" Thank god your forum exists". Yes it did demystified the "Black Art", it gave a chance to most of us including me (with your help)to build our flowbenches, years ago we could only hear to what other did and it was almost to impossible to get any infomation. In your forum there is very good thechnical infomation. I have heard of a system that speed controls the vacuum motors to your desired depression. I don

[gavinator68]

thanks for the help guys............

Now I am finalizing my plans for my bench really like the way Jeff set his up.

If you look at the JDF bench from blownalcohol



What would be the pros and cons of using the pitot tube vs. the orifice type in this set-up?

David

[bruce]

The pitot style allows an easier cabinet design since all the working pressures are inside a pipe. The orifice style allows a smaller cabinet foot print, but the cabinet has to be stronger as it holds the working pressures.

The design/plans I'm working on now started out to be a pitot style but I'm now converting them over to an orifice style and I hate to say this as I have always been a pitot guy . . . I'm going to build an orifice bench very soon. But again I feel the orifice style takes a stronger cabinet which you and I talked about on the phone.

[gavinator68]

So after all this reading and hanging around on this board........................ am I still getting the style requirements confused?

JDF's bench has a reletively small plenum............I was considering putting together a pitot style bench with a larger plenum. More along the size of 18" square by 36" tall thinking that it would be a larger area to settle the air either before it enters the tube or before it enters the bore adapter. Not to mention the ability to have a direct, srtaight line connection to the vacuum source without ANY type of bends or turns to disturb the flow. Is this unnecessarily over engineering the requirements of the pitot style bench or would it have some added benefit or reliability?

[bruce]

[86rocco]

Hey Bruce, I'm curious, what's behind your decision to build an orifice type bench?

[ThomasVaught]

Quote:

"I'm now converting them over to an orifice style and I hate to say this as I have always been a pitot guy . . . I'm going to build an orifice bench very soon."

Actually I think that now that Bruce is close on his Large blower it makes
a lotof sense to built a bench like Tony's with the blower inside. Due to
the packaging of the blower you now have a lot of room on one wall to
install a Orifice wheel like Tony has too.

(All that stuff aside, the "Orifice Guys" beat him into submission with our
far superior design!) Just kidding!

Tom V.

[bruce]

Well Tom you might be right on the "beating into submission" . . . actually it is a matter of economics the forum doesn't run for free so I have to keep adding products to support the forum. I keep machining orifice plates and selling them, but I keep thinking and have been told I need to come up with a set of plans to sell using the best ideas off the forum.

I've had a lot of requests from "lurkers" who basically don't want to spend the time searching through all the posts here and coming up with a plan. There are other plans being sold on the net (some guy is selling 2-3 sets of plans a week on ebay for $14.95 and he doesn't even have a pic of a bench) and after buying those plans they end up here for help anyways so why not let them start here with the best of all the ideas rolled into one?

The orifice bench lends itself to a simpler/smaller design with bi-directional being a plus with a swappable orifice plate. Now in order to verify my plans I need to build said bench and try it for myself. What I'm working on will still be based on blower motors and not a single blower style. For the average user the single blower is not required and to much work. That project is for the hardcore user, which most of the "regulars" have become.

My bench will be an all digital gage bench, if someone doesn't want to go digital they can come here and figure out the water gages for themselves (might add that at a later time or some forum member who wants to mess with water gages can come up with a plan). Going this route it will be a high-end home built bench. I'm trying to get the building costs down below $1000 and have a bench that rivals if not better than a commercially built bench for accuracy and repeatability at a fraction of the cost. Will this bench be for everyone? Probably not, but I feel my machined parts lend themselves to be used in the best bench someone can possibly build.

I feel there is a need out there for the home shop diy'er who wants a good quality bench and isn't being satisfied now. Hopefully that will be changing and by doing so the forum can continue to grow with the added "return on my investment" . . . hope that answered the questions?

(sorry for hijacking the original intent of this thread)

[ThomasVaught]

Well Bruce,

I am on Orifice Bench design number 316 so if you have any questions,
PM me and I will send you my e-mail info.

Since we found out our issue with the "electrician" wiring the one bench
with 208 volt vs the proper 110 volt power the flow capacity naturally
dropped in flow. It takes about 8 motors to get over 500 cfm.

Other members should be aware of that deal.

Are your plans to be geared for a guy using 220 volt power with 110 motors(Blue Bench) or the normal 110 volt power with 110 volt motors?

Tom V.

[gavinator68]

I just appreciate all the input and wisdom that is available here so................. if you feel the need to weigh in on any number of topics and veer off course a little Bruce I assure you. You have my support!!!

Lets hear it for the board!!!!!

Cheers,

David

Thanks again bruce.