splais

My Feedback: (25)

I have this smoke pump on a 30cc plane. I have it working - sort of. But I'm having a little trouble adjusting the smoke fluid flow. Could someone answer the following questions.

I'mguessing that if you put too much fluid through it, it will reduce the smoke, sort of drowned it out. If you don't put enough smoke fluid through it you get the same effect. Am I correct?

I have smoke actuation on my gear switch. It looks like I want to have the ATV (end point) set at about 65% for smoke, but I'm thinking that is still too much. anyone want to comment on this?

I'm also question I should leave the end point at 100% when the gear switch is in the "off" position, am I correct?

Thanks.

Steve

My Feedback: (54)

I always like to put a mix in on the throtle, as well as have just an on switch. The mix is for flying and the on switch is for getting the pump primed. You will notice a LOT of fluid on the tail of the plane if you are running tooo much smoke fluid. I like to max out the smoke effect, then reduce it a bit to help keep the mess off of the plane. MOST important is HEAT!! If you don't have enough, you won't get the desired effect. Some people use a heat coil to help get the fluid hotter before it goes into the muffler or pipe. For 30cc, you may even need to add a restrictor in the line to keep the fluid low enough to burn, and the pump running enough to pump. Hope this helps.

wind junkie

My Feedback: (1)

I agree with Steve, heat is key, and putting the pump speed control on a switchable throttle mix is best. The shape of the mix will probably work best with a zero point until well into quarter throttle, and then a steep curve to mid throttle and a more or less flatter curve to max throttle. You need to experiment to see what your pump and flow rates are like. Much depends on the heat available, and how good you are at getting the fluid to the right places.

I've found that it's very difficult to actually get the smoke output to diminish with extra fluid being pumped into the muffler== normally you just waste fluid which shows up on the tail as Steve says. Basically for that to happen you'd need SO MUCH fluid that it just cools all the exhaust gas and hot surfaces inside the muffler before anything smoked at all. That would be a real waste. Normally more fluid still gives you more smoke, but you just waste so much it's very messy.

A pre-heater is ok but most of the mufflers that already come with the coils in the muffler (ie slimline) are much heavier. If you have a warbird that needs nose weight that would be a good use for the extra weight.

Another good trick to maximize efficiency is to try to get the fluid to spray in a pattern which maximizes the exposure of the fuel spray to the hot exhaust gasses. I get pretty good results by making a spray nozzle from a flattened piece of brass tube with some special attention to detail filing the edge to give a good spray.

I have made some spray nozzles which give a fine set of jets 8 or 9 of them in one single tube by first flattenting the end of a tube, then sanding almost all of the flattened area away, and then "slicing" crosswise across the knife edge filed area with an old hobby knife to give very tiny orafices which each then produce a fine jet of smoke fluid.

I install the tube into a pressure type fitting with appropriate ID to accept the tube (I think a DuBro 10-32 fitting if memory serves has a 1/8" dia inside, or can easily be drilled to fit) from the inside of the muffler, and then have the tube go into my neoprene tubing which attaches to the nipple also. I use wire ties to clamp the tube within the tubing to stop vibration from sliding my nozzle out and losing it (which has happened). Alternately you could just solder the tube to the fitting, but I like to be able to remove the tube to clean it if needed should carbon build up too much.

I put my pressure fitting very close to the exhaust output, but try to make sure the spray doesn't actually point into the cylinder. Once I tried that and I was getting carbon deposits on the spark plug! Luckily, the motor never quit, but it seemed like it should have!

One thing to note is if you restrict the flow to get a spray as I have described, the amperage will rise to your pump, so you need to strike a balance between your throttle program and the restriction while knowing the capability of your pump. I put an ammmeter on my pump, and set it for 300 to 500mA at full blast setting while testing the setup outside the plane (using the pump to spray the fuel back into the supply jug and admiring the spray pattern). If you don't do that, you are likely to burn out your pump.

On my P40, I have a Tee in the line with two of these fittings to try to get a better misting into the muffler. Both planes are DA 85 powered.

JASONB2323

Thanks for the detail! That will help get a good jump start for setup.

Wind Junkie, what did you decide to use for a smoke pump battery? I have not yet installed my sullivan skywriter but measured the pump's load current while experimenting with the pump setup outside the plane. Was thinking of using a 2-cell Lipo, like 1000 mAh to save some weight as the pump is only on for relatively small periods of time. But some of the guys at my field are using NiMH or NiCad.

Can you share your ideas on pump battery selection?

Thanks!

Jason

wind junkie

My Feedback: (1)

Hi Jason. That battery sounds perfect. I'm using an old 2 cell "Common Sense" 800 mAH lipo on my P40 right now. It is about the size of a pack of Trident gum and I just velcro it to a flat surface next to my pump. It's more than enough for several sessions, but I normally charge it when topping off my flight pack and ignition batteries anyway.

Joe