Nothing provides pleasure to your RC flights greater than a smoke system. Do a loop or a roll and add that dense, long-hanging smoke path and you’ve got an airshow! As an alternative of shelling out the coin for a industrial smoke muffler, save a couple of bucks and modify your inventory muffler. Then apply your financial savings to the price of a superb smoke pump and the required {hardware}. Right here’s how I made my smoke muffler for my Zenoah G20–powered Hangar 9 1/4-scale J-3 Piper Cub.

Picture above: A smoke system is an effective way so as to add quite a lot of enjoyable to your RC flying.
proper: The inventory muffler that comes with the Zenoah G20 engine makes an important smoke muffler.

Getting Began

Take away the inventory muffler from the engine, and clear it up with some acetone solvent to degrease it. I used a brand new single-edge razor blade to rigorously take away the outdated exhaust gasket. Right here, you may see the brand new one which will likely be used after the muffler has been modified.

For plumbing, you’ll want a mixture of Tygon gasoline gasoline line and heat-resistant silicone tubing that holds up effectively to the warmth of the muffler. To switch the muffler, all you want is a big brass tube that matches into the muffler’s exhaust pipe (used as a baffle tube) and a size of skinny 3/32-inch copper tube for the oil preheat and injection tube. I used Du-Bro and Okay&S instruments to bend and cleanly lower the steel tubes. For the smoke oil tank, I used a Sullivan 10-ounce tank with a regular two-tube setup. Be sure you use tie wraps to safe your tubing. A chunk of plywood together with double-sided foam tape or Velcro makes your tank and smoke system simple to take away for servicing.

Injector Tube

Begin by bending and making ready the tip of the injector tube. To make a superb atomized spray mist of oil contained in the muffler, I used a wire cutter to snip off the tip of the copper tube; this squeezes and seals the tip and provides it a fishtail form. Use a skinny cutoff disc together with your rotary device to make a small nick in the midst of the fishtail; this produces a gap about half the dimensions of the inventory tube. Bend the tube to form in order that it’s lengthy sufficient to enter the aspect of the muffler, cross by way of to the opposite aspect, and bend 180 levels to re-enter the muffler.

Drill three holes within the sides of the muffler. Relying in your muffler and engine set up, these holes need to be customized laid out. On mine, the one entry gap is on the muffler’s aft aspect, and the 2 others are on the entrance aspect. Drill the holes barely bigger than your injection tube’s diameter. I used a drill bit barely smaller than 1/8 inch (about 0.1 in.). Utilizing a grinding bit, take away the black end on the muffler exposing the naked steel. This offers a clear floor for the steel epoxy to stay to.

Right here, the injection tube has been put in and is able to be sealed with J-B Weld steel epoxy. Clear the injection tube in addition to the floor of the muffler with extra acetone, and when dry, combine up some epoxy and construct up neat fillets across the tube/gap areas. Clean the fillets with a moist finger after which set the muffler apart to totally treatment (about 24 hours).

Baffle Tube

Growing the steel space to assist switch the warmth to the smoke oil throughout the muffler produces denser smoke. The simplest approach to do that is so as to add a baffle tube. Slip a snug-fitting brass tube into the muffler’s exhaust pipe; the tube needs to be longer than the exhaust tube already throughout the muffler. Slip the baffle tube into place till it bottoms out in opposition to the within of the muffler, and mark the size. Use a Okay&S tubing cutter, and lower it to size.

To find out the size of the interior tube, bend a chunk of wire as proven and slide it into the exhaust pipe. Really feel for the tip of the interior tube, and together with your thumbnail, use the wire as a depth gauge. Switch the size to the brass tube.

This small space on the finish of the brass tube is the baffle part, and several other holes should be drilled by way of the tube. I used a 1/8-inch drill bit to drill eight holes across the finish of the tube. Take away any burrs from the holes after which sand easy.

Slip the baffle tube into the muffler till it bottoms out and is flush with the tip of the exhaust pipe. Drill a gap within the aspect of the pipe and thru the tube, and safe in place with a panhead sheet-metal screw. Loosen the screw barely, add a drop of pink thread-lock, and retighten.

Reattach your DIY smoke muffler to your engine, and if essential, trim the engine cowl in order that it doesn’t contact or intervene with the smoke plumbing.

Inside Setup

A detachable smoke system is an effective technique to go as you may take away the general system for servicing. It’s a lot simpler to work on all the things exterior of your mannequin than with it crammed into the fuselage. For my Piper Cub, I merely eliminated the cabin particulars and seats, and used the pilot space for the smoke-system set up.

That you must regulate your smoke-fluid movement. Injecting an excessive amount of smoke oil into your muffler is worse than utilizing too little. The surplus oil really cools your muffler, and this reduces the quantity of smoke it generates. This additionally shortens your “smoke-on” time by burning up the fluid quicker than wanted. I used an auxiliary needle-valve meeting from an outdated glow engine to fine-tune the quantity of oil getting into the muffler.

Be sure you use gasoline filters between your smoke tank and your switch pump. Strive to not swap in your smoke pump when your engine is at low throttle or at idle; this could trigger the engine to drown on the unburned oil, which will increase again stress. A good suggestion is to combine the smoke swap together with your throttle channel and set the “on” place to 1/4 to 1/3 throttle.

Remaining Set up

Drill a gap within the firewall, and route your smoke strains into the cabin space. A stiff size of wire fed by way of the outlet can be utilized to information tubing into the cabin. Connect the smoke line to the wire, and pull it into place. On the muffler finish of the smoke line, insert a brief size of aluminum tube and slip on a 1-inch-long piece of glow-fuel silicone. Connect the silicone tubing to the muffler’s injection tube. Silicone stands up effectively to the muffler’s warmth. Join the smoke line to the needle-valve meeting, and join the needle valve to the output becoming of your smoke-oil pump.

Connect the smoke-oil tank to the pump’s enter becoming, and plug the pump’s energy lead into your receiver. I take advantage of a T-fitting between the tank and the pump for filling and emptying the tank, and use a gasoline dot to seal the fill tube. Be sure you additionally connect a vent tube to your smoke tank, and route it out of the fuselage.

Try the smoke density! That is what it seems to be like when the oil movement is decreased (just one flip open). This provides an important “smoke-on” time, and my 10-ounce smoke tank lasts for greater than 10 minutes.

Give this system a strive! This DIY smoke muffler works simply in addition to any commercially accessible muffler. Smoke on, and have enjoyable.

TEXT & PHOTOS BY GERRY YARRISH