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3D printed beam mount .049 backplate Empty 3D printed beam mount .049 backplate

Post  Jason_WI on Sun Oct 13, 2019 6:33 pm

Any interest in a 3D printed beam mount .049 backplate?

It should have the same crank shaft center and the drive washer placement as a  TD .049. The cylinder will be offset though. Can use a 128 or 80 TPI NVA assembly from a horseshoe/postage stamp  backplate.

Can start with a reedy then transition over to a TD without any modifications.

3D printed beam mount .049 backplate Beam_m12
3D printed beam mount .049 backplate Beam_m13
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Post  batjac on Mon Oct 14, 2019 12:35 am

I can see it having an interest for profile CL, not so sure about R/C. I'd buy one. Not sure that I'd buy more than one, as I have plenty of TDs/Medallions. Of course, I haven't seen the finished product either. With a TD piston and cylinder, I wonder how it would compare against a TD or a Medallion.

The Specualtive Mark
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Post  dckrsn on Mon Oct 14, 2019 10:37 am

bounce bounce bounce  
Definitely interested.
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Post  Levent Suberk on Mon Oct 14, 2019 11:37 am

Yes, it is easier to mount reed engines on profile fuselages.
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Post  944_Jim on Mon Oct 14, 2019 7:16 pm

Mmmmm. Interesting concept. I'd be in for at least one, if not a few.

Thanks for developing this!
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Post  Marleysky on Mon Oct 14, 2019 8:06 pm

OH sure! I'd be in for a couple. I've a couple more NV laying around!

Really looking forward for the Turbo Head's....Greg...Hint, hint, nudge, nudge...
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Post  dckrsn on Mon Oct 14, 2019 8:59 pm

Jason, I'd be in for at least 2.
Once again, the 128tpi will be the way to go.
Glad I started hoarding postage stamp plates
years ago.
Tnx,
  Bob
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Post  Jason_WI on Tue Oct 15, 2019 1:03 am

Here is one printed. Need to size the holes and polish the reed seal surface.

3D printed beam mount .049 backplate 70474110
3D printed beam mount .049 backplate 6f4fba10
3D printed beam mount .049 backplate 13155210
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Post  1/2A Nut on Tue Oct 15, 2019 1:58 am

Jason this is a great fix for profile planes in general eliminating
the flat plate firewall. I would consider moving the beam back
so you have maximum possible strength. Would be a bummer
to end the day from a prop strike which happens all the time
with CL planes. See pic for reference, think a ground smack
could sacrifice a prop blade rather than one of the beams or both.
3D printed beam mount .049 backplate 70474110
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Post  Jason_WI on Tue Oct 15, 2019 3:22 am

I was trying to keep the same drive plate position and crankshaft centerline as a TD .049. I can see where the unsupported ears can get broken easily.

3D printed beam mount .049 backplate Bd96ca10


I can certainly move the ears back and add support for the NVA like this.

3D printed beam mount .049 backplate 0d2a1010


If durability is more important than compatibility I can certainly have that option too.


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Post  1/2A Nut on Tue Oct 15, 2019 3:53 am

I like the updated drawing you can access the NV nipple for ease of refueling
without flooding the engine. But but but the shortest distance from venturi
to reed valve will yield the most influx / power. The long stem requirement
for integrated fuel tanks robs power. Think Sportsman series how the design
improved influx.

Yes knowing how brutal CL flying is on props for the 1/2A size planes
the break rate in levels leading to engine damage:
1st - prop
2nd level - bent 5-40 prop screw
3rd level or degree - beams
4th worse case  - crank or pin or ball socket

Note you have a chance to make a RC version for the Cox RC carb or for any aftermarket RC carb
that uses the TD carb body threads. Such as the Tarno RC carb.

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Post  Jason_WI on Tue Oct 15, 2019 7:38 pm

How's this? Added gussets and moved the NVA back.

3D printed beam mount .049 backplate Beam_210
3D printed beam mount .049 backplate Beam_110
3D printed beam mount .049 backplate Beam10
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Post  1/2A Nut on Tue Oct 15, 2019 9:47 pm

Yes Jason looks good!

You can improve strength as shown / no reason to keep curved surfaces on the outside.

3D printed beam mount .049 backplate Beam1010

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Post  Jason_WI on Wed Oct 16, 2019 1:52 am

It runs!

With the .2” intake it was hard to get started but once it ran it barked pretty good swinging the Cox grey 5x3 prop and 25% Cox super power fuel.




A few pictures of the latest design.

3D printed beam mount .049 backplate 2a37f510
3D printed beam mount .049 backplate C513df10
3D printed beam mount .049 backplate 14d89d10
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Post  1/2A Nut on Wed Oct 16, 2019 2:32 am

17, 684 - peak 17,845 good runner nice and steady.
They are always a bit fussy when gold and normally
have a bit of gravity flooding in the case till the engine
is running. I use a Hornet 1/2A starter run it up without
the glow plug hot to lean out the mix in the case tends
to start up the cold ones in short order after that.
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Post  aspeed on Wed Oct 16, 2019 5:19 am

Interesting idea there.  Is it the same bolt pattern as the TD?  Some guys would probably like it if there was a built in drum valve throttle/choke like the Cox one, except not sticking out so far. Maybe a horizontal hole across the back where you removed material. Even an air bleed hole provision.  Just thinking out loud. Just roughing out a rotor hole that could be reamed out later for a stock brass size like 1/4". The first design looks great with the forward beams but there would not be much room for a throttle behind. I think that would be a seller, not thousands?
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Post  Jason_WI on Wed Oct 16, 2019 3:11 pm

Basically a choke tube type throttle. I thought those didn’t work to well with SPI cylinders. Tarno carbs recommended the use of a muffler for best results.

I can certainly update the back of this current design to integrate a choke tube. Probably work best with non SPI cylinders like the #3 I think.

Here are pictures showing the support material and the cleanup of the current part.

3D printed beam mount .049 backplate 9fd77110
3D printed beam mount .049 backplate 4d878f10
3D printed beam mount .049 backplate 4bded510
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Post  NEW222 on Wed Oct 16, 2019 6:29 pm

Wow. That thing looks very strong! Another great job there! I really like the pictures of the backplate as it is being printed, or is that what it is? Regardless, the pictures are great. Thanks for sharing.
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Post  Jason_WI on Wed Oct 16, 2019 7:25 pm

Here is a version for a Tarno carb. Would need to drill part way in to 7/32" then tap with 1/4-32 bottom tap. Has to be flush as the carb is threaded on. Would not fit on a standard TD firewall mount as the carb would stick out the back too far.

I'm not going to move any further on a choke tube version. Too many critical fitting parts that would be ripe for air leaks using 3D printed parts. Bernie sells this choke tube throttle that could be removed form the sure start tube and fitted to the back of the tarno mount. Would need to drill the hole for the spraybar then too.

https://coxengines.ca/throttle-conversion-for-cox-049-engine.html

3D printed beam mount .049 backplate Beam_410
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Post  aspeed on Wed Oct 16, 2019 11:18 pm

I was thinking just the shaft that the horn bolts to and the c clip, not the whole housing that goes with it. It would take drilling a few holes for sure.
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Post  1/2A Nut on Thu Oct 17, 2019 1:14 am

I have removed and tested the Cox air choke on a project it does get the job done.

The benefit of the size of it makes it suitable for a compact presentation.
The Cox and Tornado RC Carbs extend the fuel metering further away from
the reed which begs the question which will produce more RPM out of the
three types.

Interesting tidbit of engine tinkering nirvana to test a threaded version and
smooth bore version could be done. I have used Loctite 638 with a TD .020
and a smooth bored aluminum carb body for a G-Mark .03 carb worked like
a champ to hold and seal with no degradation over time using high nitro.

Seen used here a past engine of the month winner 10/2014
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Post  getback on Thu Oct 17, 2019 7:55 am

That looks good Jason to incorporate a carb without a lot of hassle would be great , Are you going to put one together and run it ? This Site Rocks!
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Post  Jason_WI on Thu Oct 17, 2019 7:21 pm

I need to find my 1/4-32 tap or order a new one.

Used to be able to buy the AP .061 carburetors pretty cheap and run a 1/4-32 die on the mounting base to put threads on for use on a TD. The source for those has dried up. Not sure what the stock status of the TD RC 05 carburetor is at Cox International. If it's even worth the effort to change the design to mount the carburetor at a 45 degree angle kinda like a queen bee. Hopefully not turn it into a paper weight like the queen bee that is being anemic on power. This would shorten the design up a bit by doing this and would still allow the use of a TD venturi and spraybar for CL use.  There are lots of horseshoe and stamp backplates out there to rob the NVA assembly from for little cost VS a Tarno carb, TD RC 05 carb, or TD venturi assembly.

My main focus for the beam mount was for the profile CL plane use. If R/C was needed then use a throttle ring on the cylinder.

I have 4 of the standard NVA beam mounts available for testing. If you are willing to run one and report back the results with any issues good or bad I will send you one. First come first serve via a private message. You will need to install your own NVA assembly (80 or 128 TPI), reed, circlip, and gasket.

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Post  1/2A Nut on Thu Oct 17, 2019 7:53 pm

I will test one and report via a vid and performance results.
PM sent, look forward to it thank you Jason.

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Post  1/2A Nut on Thu Oct 17, 2019 8:05 pm

I have the Queen Beast that now makes more power then a TD .049 - .051
Truly between the .049's and the .09

Cox Queen Beast .074 / Kamtechnik Turbo Plug Adapter Test

With Muffler and pressure tap APC 6x3
Static Peak 19,783 rpm  / .214 hp - 158w / 56.2 mph pitch speed
Impressive 23.3 oz thrust!
OS P4 turbo plug / 25% nitro / 20% oil
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