I've got a question for you guys. For Treaty combat, I need to restrict the flow of my pump to 1 GPM. I am using a BC pump atm, which is set up with a 1 unit restrictor for fast gun use. I'm looking for an easy way to regulate my flow, while making it easy to change back to fast gun format. What I have been thinking about is taking a small square piece of plywood, and drilling a hole in the center and attatching it to the base of my pump. I could enlarge this hole until the GPM is correct for treaty battling. I could then remove this "restrictor plate" when battling fast gun so I could have unlimited inlet flow. My main concern with this idea is that if I slow the amount of water coming INTO the pump, it will cause the pump to work incorrectly. I don't have enough experience myself to say for sure that there would be an impact, so I figured I'd ask you guys. Thanks for any help or other ideas you guys may have for regulating my flow easily. Mike D
Your concern is correct. For pumps, you need to restrict the outlet side, not the inlet. Restricting the inlet causes a low suction pressure, which causes cavitation, which damages the impeller. I'd use a replaceable restrictor, on the outlet side.
Personally, I'd buy a cheap forward only ESC & a servo tester so the whole thing is controlled electrically by a POT. Oh wait, that's what I am doing! [)] Here is the thread with more info on the servo tester: Visit this site You can also google them & there are a whole host of them available for around $20.
My suggestion follows: For flow regulated cases, remove the restrictor (this reduces the current draw of the pump). Pick an outlet size that fits your superstructure and minimizes the stream of water coming out. Use one of the ESC's with the pot controlled box like justin said. One note, some pumps may have trouble if they don't have enough back pressure (not generally in running mode but in spool up with vapor lock due to the decreased impeller speed). For these flow limited cases, my preferred way of dealing with it would be to have the pump spool up at max throttle for ~1-2 seconds and then spool down to the standard operating speed (will need to be repeated if pump sucks air) (although the legality of this alternative in the rules might be in doubt). The other option is to restrict the flow to the point at which one can run near full throttle. If one of our electronic guru's had some free time, it should not be too painful to design a controller circuit that monitors current draw of the pump and intelligently adjusts the esc based off some desired end condition settings. This would allow the pump to compensate for a cavication/air sucked in problem appropriately. You will find that a cavicating pump generally pulls significantly less current than the same pump operating properly. As some of you know, I make pumps and much of this comes from experimenting with my prototype, gen 1 and gen2 pumps at various different conditions. Other pieces of wisdom I found was that a motor that vibrates a bit more will tend to vapor lock less... at least in my experiments. not sure why, but I have some theories....
What I've done is to drill & tap a hole in the outlet tip (ref: Swampworks pumps) perpendicular to the flow & put a setscrew in there, It's pretty easy to tweak the rate down to whatever is needed. JM
I fitted a small plastic irrigation tap to the outlet of my pump to cut it back to the legal rate, the excess merely vents thru the priming hole in the pump.
