combatpigg

My Feedback: (3)

The backplate cover is too thin to tap threads into, but it is possible to attach a 3/16" thick disk of aluminum into the circular recess of the backplate. A pair of 2-56 countersunk screws and a smear of JB Weld will hold the disk to the backplate. I ran something similar to this idea for many years on Fox .36s [to mount pressure regulators] and never had a screw back out inside the running engine.
Once the extra material is added to the backplate, then drill and tap for your pressure fitting.
Within reason, the size of the pressure tap hole isn't critical......contrary to Urban Legend.....you don't need to do any solder backfill to make a pin hole sized orifice.

fit90

I am glad to learn the hole in the pressure fitting is not critical.  I can't tell you how many #65 and smaller bits I have broken trying to keep thst stupid hole small.

Thanks for the heads up, much appreciated.

Bob

phatboy

This thread is full of win!

CP you are helping me figure out a great deal about my upcoming build of my GLH.

Does the ASP not come with a needle valve that could be remotely mounted? Why did you have to modify it?

Also Im not sure what you meant by the venturi being round stock? Did you have to decrease the size of the hole in the intake?

Thanks for your awesome diagrams! You rock!

aspeed

We used to solder the hole up with a piece of waxed .010" wire in, and then pull the wire out.  I looked at the fitting coming from the lug and thought it was a lot of farting around. but a nice result.

combatpigg

My Feedback: (3)

PB, by roundstock I meant that the venturi was machined from a hunk of round aluminum bar stock [roundstock] that was laying around. I've also made them out of nylon. The venturi in my Cyclon I made from black nylon. In that case I wanted to try a taller venturi for a tuning effect.
The stock ASP carb could be dismantled and you could adapt that needle assembly for a remote mount, or mount it directly to a custom made venturi.
In my case I didn't want to mess with the brand new ASP carburetor.
I like how compact the Cox NVAs are when mounted back at the firewall.
Next time I'd like to plan it so that the needle doesn't hang out so far.
The problem is the discharge nipple has to point forward and it can't be jammed against the back of the engine.

phatboy

I am a bit confused. What part exactly is the ventury. I guess I was considering the area where the carb attaches as the ventury. Im trying to get caught up on the lingo.

phatboy

Double post sorry

smoknrv4

My Feedback: (11)

Tinkering with my Magnum 15 this week, to try in my Shark 15 plane.

combatpigg

My Feedback: (3)

Very nice...! Where did the brass fittings come from...?

You'll really like it. With a well padded fuel tank your fuel feed will be steadier than ever.
Prolonged dives will still be a problem, but the only cure I know for that are those troublesome latex bladder tanks.
Are you going to use a shutoff..?
I've used a servo to pull the fuel line back through a hole in the firewall to pinch the line.
A "fail safe" idea is a flood-off. You need to bypass the needlevalve and use a servo actuated valve to hold the bypass line closed until it is time to kill the engine with too much fuel.
It could even be used as inflight mixture control. I've never been able to find room for this idea in a cramped .40 sized plane, but someday I'd like to make it work.

combatpigg

My Feedback: (3)

The venturi is the piece that replaces the carburetor. Some RC engines are sold with an optional control line style, single speed fuel feed. Most control line planes run at a single speed until the fuel runs out.
For RC Speedplanes, this is superior to a bulky carburetor that is impossible to hide inside a cowl and carburetors restrict the maximum hole diameter that you can feed the engine with.

mikegordon10

Would that be a homemade venturi?

smoknrv4

My Feedback: (11)

I made the venturi on the lathe with some aluminum bar stock, and the throat diameter is 6mm, which is just a few thou smaller than the crank opening width.

CP the brass fittings are the ones off the muffler and the original carb....they were handy.

Now i just have to wait for the weather to warm up a bit to try it out. I've also have to steal a RNV assembly from another engine or something.

CP I'm using a 4oz JETT bubbleless tank in the Shark, so vibration usually doesn't bother them at all.

phatboy

Do you have a thread on the shark?

CP you are really helping me alot here, this thread is awesome.

smoknrv4

My Feedback: (11)

Here's Rain Daves build thread.

Pics of mine are in post # 125

http://www.rcuniverse.com/forum/m_79..._1/key_/tm.htm

Sorry CP for highjacking your thread.

phatboy

Speaking about the venturi for the ASP .12. I assume since you made one that it doesnt come with one. I have no way to make one of these myself. That poses a small problem for me. Can you buy them seperate?

Also, I understand the theory behind running with no muffler. Would it be possible to just run a short head pipe to get the exhaust a little farther from the plane or would it not be worth it? Its to easy to just wipe the plane down after a run I guess.

On the Magnum, Smokin...Did you just retap the threads for the back plate in order to screw the fitting in there. Were any other mods necessary?

combatpigg

My Feedback: (3)

Don't worry about it. That's why they call these topics threads...my threads are / should be open conversations.

The Magnum .15 should be at the top of the list for bang for the buck value. 6.5x5 prop on a small speed plane will get you 130 mph.

combatpigg

My Feedback: (3)

It's handy to pick up a $20 caliper at Harbor Freight.
With this tool, I could measure the opening on the Magnum case and then see if a C/L venturi off a OS .15 would fit.

You actually don't need a lathe to make a venturi, just a drill press or a drill motor and the shank of a hard steel screwdriver or wood chisel held against a solid tool rest as your cutting tool. The inside cuts can be done by grinding a profile on your chisel.

phatboy

Hey CP. Here is a picture of the new ASP .12. Notice the head? Its almost twice as tall as the one you are using on your plane. The nose on the Stock GLH is not as tall as the one on yours. With this engine it will stick up fairly high above the top of the nose. Do you think that would be a problem?

Also, I am pretty handy with a vice and a dremel tool. I imagine I could make a venturi with that!

combatpigg

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I used my drill press and a flat milling bit to mill some of the height off those fins.
I don't see it as a big deal on a 100 mph plane.
It would be way more of an issue at 150 mph and really critical at 200 mph.

phatboy

Cool I just ordered a .12

I will start my own build thread when its time. School takes priority tho!

Scota4570

Just food for thought....I made an airplane simmilar to yours in the 70s. It used a Cox medallion 15. It seemed pretty fast to me. I would bet a TD 15 could be had to beat for this application.

combatpigg

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I've never seen a TD .15 in person. I wonder how much they weigh...?

I've seen a few Conquest .15s, but never a TD.

aspeed

A friend of mine had a Tee Dee .09 on a GLH and said it went good.  I have one, it is pretty light.  I am on a holiday and can't weigh it right now.  The power was quite good for the time.  An AP .09 is only slightly more powerful with no muffler.  The .15 would be a bit better.  I haven't seen one for a long time.  I just picked up a Cox Olympic .15 at a swap meet here last week, that would weigh about the same, but would be down on power from the Tee Dee.  The Cox Conquest is in a different league but would be a bit heavier.  The AP .15 or .09 would be an ok candidate for the GLH.  They are fairly light, pretty much the same motor as the ASP.12. Almost exactly the same except for being a rear exhaust.

combatpigg

My Feedback: (3)

The .09 was a good engine to pep up any 1/2A design that ended up under powered.
I built a $19.99 Hobby Shack SST and it was pathetic with a TD .049 but flew nice with the .09

combatpigg

My Feedback: (3)

Got a flight in this morning with the 5x5 prop.
The engine seems to handle it on the ground about the same as the 6x4 MAS, but it doesn't unload in the air like the 6x4 [actually 5.75x4] did.
It was 38 degrees with a steady breeze. My recorded passes were in a 10-15 MPH wind so the numbers are inflated by that much. At any rate it is fun to see the plane whiz by that fast.
2 passes recorded 133 mph and a pass right before shutdown hit 142 mph.
This plane is about as fast as a delta I built for a ASP.12 and much easier to launch, that's for sure.
I'm inspired to build more of a special purpose speed plane for this engine now. It will still be focused on being cheap and simple to build.