Depression Control - How do you size for it?

[115-1172523331]

[color=#000000]I have been reading about 100 posts and redesigning my bench about as many times and have decided that it is time to

[bruce]

Look at the RV gate valves, I use that on my bench not as a a bypass valve but it does give good control and fine tuning of the flow depression.

I'm planning on trying the bleed valve in the very near future on my current bench instead of the a flow shutoff type. Eventually setting up to use a PWM valve with my FP1 as soon as I get one built.

[115-1172523331]

Thanks Bruce! My problem is trying to figure out what size the valve(s) should be. I am running small engines (100cc/6ci) and to date have had a max flow of 60cfm (using a friends Audie QuikFlo and my shop vac). I'm building a "proper" motor box bench and 1 motor should be pretty close to giving me all the flow I need (but I'm putting 2 in and planning for 2 more). With a 2 inch flow element, should a bypass valve be 2 inches? That is about the smallest RV gate valve I found, but I haven't looked too much!

My plans don't include blowing (having been convinced that sucking through the exhaust is a real option) so the plumbing should be simple. I'll try to make a readable sketch and post it later. -- Doug

[bruce]

Check Home Depot or Lowes they should have the same valves in the plumbing department in various sizes. I bought my valve at the local hardware store.

By using a threaded rod connected to the valve handle you can make a nice adjusting setup to give you fine adjustment so valve size is really not a problem.


Something I would like to change that I have not done yet is the threaded rod, I'd go with acme thread so it doesn't take as long to make adjustments. Not fond of blocking the flow either, I haven't had problems with it but it doesn't seem natural to me. A bleed valve I think would be a much better design.



Edited By bruce on 1174954338

[115-1172523331]

Hi Bruce, Thanks for the pics! This is sure a clean way to valve the bypass! I'll look at some sizes at the hardware store tomorrow (Lowes and Home Depot are over an hour away, so limited travel to them). I have to think that someone out there has a bypass system on their bench and could at least give me flow rates and bypass size. Then I can better guess what size I need. Thanks for your input!

Doug

[1960flh]

Doug;

If travel is an issue try these guy's, i got my valves from them with little effort.



Also have you thought of using a motor speed control you would only need to connect it to one motor?

Rick

[115-1172523331]

Thanks Rick, Even if I don't use the valves, I will be getting some of the flanges. I want to have a bolt-in flow element so I can change down to 1-1/2 from 2 inches and was going to make flanges for my pipe. I can just get a couple sets of these and use a reducer for 2 to 1-1/2 to attach to the plenum outlet and vac chamber inlet. I haven't considered motor speed control because I don't like "playing" with electricity. A mechanical control device is just my ticket and controlling bypass air doesn't change the load on the motors. I may try my stepped pipe "valves" just to see how it works. LOL -- Doug

[Thomas Vaught]

I have used "tongue valves"/ "slice valves"/
"toilet valves" in the past for air control applications (intake and exhaust).

What I did was get two valves for the intake and two valves for the exhaust. I mounted a pair of the valves flat to the side of the plenum box on the intake side (which fits inside the flow bench) and a pair on the exhaust side.

The valves were far enough apart that a threaded rod can pass between the two valves.

I had a rod support at the bottom and the support at the top. The valves were connected with a piece of flat stock using nuts and washers and had a large female acme thread nut in the center. The rod was solid stock (not threaded rod). A male acme threaded piece was pressed on the solid rod material at the right location. (All I had to do was buy a section of the acme rod and drill a hole down the center on the lathe).

A very few turns on the solid rod would move the pair of valves a good distance.

The exhaust was a duplicate of the intake side.

I have a drawing for the design at work (excel) and if I can find it I might have Bruce or Rocco post it for me.

For the bleed valve I normally used an automotive throttle body with a valve or valves.

I am looking for the valve for you Bruce.

Tom V.

[115-1172523331]

Tom, I have been trying to figure out what you are describing and having trouble. Did you find the drawing (or pics)? What airflow does your bench run and what are the valves sizes? Maybe my nomenclature is off, but you say you normally use a throttle body for bleed, what do the slice valves do? I am calling a secondary inlet to the vac chamber, not passing through the head being tested or the flow element, a "bleed". Is this right? Thanks for all the inputs! -- Doug

[1960flh]

Doug instead of emailing you I thought I would share this with everyone in the true low budget DIY mode like many of us are. If you are only trying to control the depression through one motor this will work great. I stopped by my local store and bought one last night and it is variable from 0 to full speed so it will work for you just fine. You will only have to switch between suck and blow mode if your bench is designed that way.

I ran the Surplus center motors and the new two stage GS/Ametek motor no load and full load with no issue. SO this is a good cheep option.

Rick

[115-1172523331]

Thanks Rick, I actually took a break from building the bench this week as I couldn't find half of my tools! :laugh: I have organized (again) and will be back to doing fun stuff tomorrow. I have friends going to El Paso (Harbor Freight there) on Wednesday so I will have them pickup one of the controllers. (Or this may be just the extra excuse I was looking for to hop on the bike and head for HF in Las Cruces!)

Hope to have some preliminary pics later this week, but then need to do some preseason preparation for the first race weekend (May 5-6) at El Mirage. This may be my only chance to tune prior to Bonneville (unless you count the runs down the street in front of the house). Thanks again for all the help! -- Doug