Rcpilot

My Feedback: (78)

I need to make an intake for a new engine I've been playing with. This is a piston ported engine, so the carb is on the side. It needs to bend 90 degrees and point the carb opening towards the back of the plane.

I have a bunch of 1/2" thick x 2" wide G-10 epoxy board. I am thinking about sandwiching 4 layers of this together to make a 2" x 2" x2" cube. This is how thick it needs to be in order to mount the carb on one end. There will be a hole drilled through it to match the venturi size on the carb. The hole would have to turn 90 degrees at the cylinder end.

I'll need to attach another piece of the 1/2" thick material on the cylinder side so that I can mount the brick to the cylinder.

I will need a gasket between each layer of the epoxy board to make it seal. And I think I'll have to run a bunch of 4-40 bolts through it to bolt all the layers together.

Think it'll work?

arobatx

"will it work?"........I freakin hope so   A 90 degree intake out of G10 would be cool!  Have you played with some of Toni Clark's 90 degree intakes?  Pretty nice, not G10, and not cheap!  I can see where you would want to try fabricating your own.

soarrich

My Feedback: (98)

I think it will work. I bought 3/8" phenolic board to make carb mounting blocks , and enough to do just what you are going to do. I'm going to build a speed plane using one of my MT62s, what are you planing?

Tony Hallo

Consider tuning the length for increased performance?I believe I read 7" is about the right length of runner.

Rcpilot

My Feedback: (78)

I've been wondering if a high quality epoxy could be used to laminate the 4 layers together instead of using all the little 4-40 bolts. I'm thinking I could scuff the surface of the G10 with some 80 grit and then use a West Systems epoxy to laminate them together.

I'd want to laminate 2 pieces together and make the top half. Then laminate 2 more pieces together to make the bottom half.

The 2 halves would be put together, but not glued. I'd need a couple alignment pins through the assembly during the drilling process. Run the alignment pins through the 2 halves and then drill the holes from the top and the sider to make my 90 degree turn.

Take the pins out and separate the top and bottom half. Radius the corners to smooth flow.

Now laminate the top and bottom half together so it's one solid block 2x2x2 with my hole through the inside.

soarrich

My Feedback: (98)

I think that would work.

You might want to form the channels with the G-10 rather than trying to carve them out of it. Just drilling a small hole through it might change your mind, and dull your drill bits. I got the Phenolic board because it will be easier to work with.

Rcpilot

My Feedback: (78)

Thats not a bad idea.

I have drilled the G10 before. It's not bad if you go slow and apply the right pressure so the bit cuts continuously and never gets a chance to just spin around in the hole without cutting. Thats when they get hot and ruined.

Rcpilot

My Feedback: (78)

It's just an aerobatic plane. I want the carb turned 90 degrees for ease of cowl installation, ease of engine tuning while it is running and also I don't want the hole in the metering diaphragm cover pointing at the prop blast. The 90 degree bend will solve all these issues.


I thought it had to be as short as possible? 7" length seams like a long ways to make the vaporized fuel travel. Seams like starting would be a pain in the butt. Is that 7" length a "universal" number for all engines? Or is that dependent on the engine displacement? I'd need to know the EXACT length to use in order to optimize it. It's not like I can adjust the length of a G10 epoxy intake very easily.

But consider this:
I have NEVER messed with tuning the intake, so I have no idea.

I HAVE used tuned pipes on a few engines and I know it works very well if you actually TUNE them.

soarrich

My Feedback: (98)

Ralph Cunningham sells a rotator block out of G-10 that leaves the carb in the same position, but rotates it 90*, I have one on my SD Extra 260 works great.

7" probably would be less than a 50cc gulp the engine takes so that wouldn't be a problem, it might help in having better fuel vaporization.

4 cycles tuning the intake like the exhaust, longer for lower RPM and shorter for high RPM, but I don't know if that translates into 2 cycles. I asked a guy with one of Tony's intake manifolds on a G62 if he got tuning effect, but he never responded.

Rcpilot

My Feedback: (78)

Ralph did the conversion on this engine. The carb has already been rotated so the throttle push rod is lined up. It's nice and it runs good, but for some reason he didn't provide enough of an insulator between the carb and the cylinder. The carb is actually seated against a gasket that is in direct contact with the metal on the cylinder. The carb is vapor locking due to heat transfer.

I want the 90 degree bend like the ones Toni-Clark sells. But I don't want to pay $60 odd dollars or more to have it shipped here. It wouldn't bolt up to my engine flange anyway. This is a different engine altogether.

I plan to attempt the G10 90 degree intake manifold this week. I'll take pictures of the process and post here.

EDIT:
Pics posted. The G10 block you see in the pics is not thick enough to space the carb away from the engine. Underneath that carb is a thin gasket and then there is direct contact with the aluminum cylinder. The G10 is only a ring used to capture the intake neck on the cylinder and provide holes for the threads to bolt up the carb. If it was 1/4" thicker it would probably insulate the carb and it wouldn't vapor lock.

But I can't blame Ralph. He custom built this engine for somebody else to THEIR specs. The guy had a REALLY narrow cowl and wanted the carb as close to the cylinder as possible. So thats how Ralph built it. The guy ended up selling the engine to me after he stored it in a box for a few years. He never used it, so I was happy to purchase it at a good price since it was basically a new engine.

I could send it to him and ask him to fix it. But I'm laid off and don't have any money to pay him for the additional work. [] I DO got a big block of G10 and a LOT of spare time right now though.

arobatx

.....maybe use solid carbon rod for alignment pins, and glue them in when the layers are laminated. It might help with vibration resistance.

Antique

My Feedback: (4)

I see the carb attached tothe G10 and the G10 attached to the engine block, but can't see where themetal of the carb is touching the metal of theengine block. ????

Rcpilot

My Feedback: (78)

On the flat mating surface where the carb is bolted to the engine. The spacer is flush with the engine metal, so when you bolt the carb on it's sitting right on metal.

Antique

My Feedback: (4)

Now I see ..........

dirtybird

My Feedback: (5)

You might want to glue the G10 together with silicon seal. It makes a good gasket as well. You just need to reinforce it with a couple of bolts.
Silicon Seal has a high temperature rating. I have used it for sealing exhaust systems.

Tony Hallo

While looking for tune information for a friends Quadra 35 I found this on the intake length [link]http://www.fly-imaa.org/imaa/hfarticles/engines/v1-1-16.html[/link].

soarrich

My Feedback: (98)

Tony

This may work, but.......



>>First, aiming the elbow mouth foward gives the carb some ram affect from the prop blast.

This will give problems with tuning. The 3W engines come with a snorkel, they always point backwards. I think you could put the snorkel pointed forwards, because it has a pressure line going to the diaphragm of the carb so it senses the pressure at the mouth of the carb, Ralph Cunnham does this on his race engines, but it is a special applacation.


>>Second, it adds a slight "tuning affect" to the carb intake to increase the breathing efficiency.

There is only one carb I ever heard of that you could tune across the venture, that is a Weber, very expensive used on the GT-40/Ferrari type cars in the '60s.

>>Third, the extra length of the carb throat, plus the 90-degree bend, tends to trap the fuel "spit-out" and re-feed it to the engine.

This I believe.

Tony Hallo

If I were building a model for maximum speed and power, the airlet would placed so that forward motion would increase the air inlet pressure and decrease the temperature to provide maximum power. In our case, it's simply easier to buy the next size larger engine, this was not an option in the early 80's. The Quardra 35 and 42 were it. Planes I flew in 1990 with a Q52 now have 100 twins. There's really no need to work for more power, just get a bigger engine.

Did you ever hear of tuned port fuel injection? Just about every automobile engine today has long tuned intake runners.

The larger engines with the check valve do not spit much anyway so that's not much of a problem.

My point, if RC Pilot is making a longer intake runner, why not get it the right length?

soarrich

My Feedback: (98)

Yea, I had a '63 fuelie Corvette.

The engines have fuel injection, or the long intake runners are after the carb.

If you mean reed valves, I agree.

I don't remember the formula, but the Vette's runners where about 15" long, the runners on a 413 where about 24" long, the carbs where out past the sides of the block. Unless he's willing to fit in a 24 inch intake, shorter is better, not to mention weight.