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Glow Plug for the G-Mark 03

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Help! Re: Glow Plug for the G-Mark 03

Post  MauricioB on Sat Mar 10, 2018 9:14 pm

gkamysz wrote:Mauricio, if you can't see the image, it's your browser. It refers to an image in my google photos. https://photos.app.goo.gl/kIl9mNuOmqhSVydU2
I probably wouldn't make two types of heads for Gmark .03, only one. I could make one and sell it, but to make it worth my time it would cost a fortune.

Kris, It has three fins now and I was going to start with volume equal to stock. I should get to make a few for testing next week along with TD.020 heads.

Now with that link I can see it.
Do not worry, only those who can do it without complications and without taking your valuable time bucaba.
I appreciate all your goodwill .... time is something important, valuable, I believe ... I think so ... Thumbs Up
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Help! Re: Glow Plug for the G-Mark 03

Post  MauricioB on Sat Mar 10, 2018 9:18 pm

NEW222 wrote:Thanks for teh new picture Mauricio. I now see my 'thumbtack' was the needle. My bad, and now I feel stupid. Doh!  I should have known....

No friend, you are not stupid, do not feel this way, not everyone has the humility to ask ... that is a huge gesture on your part. Any question is always well received from me, asking is synonymous with learning.
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Help! Re: Glow Plug for the G-Mark 03

Post  getback on Sun Mar 11, 2018 9:31 am

Greg , did you make bird cages for the Space Hopper?? Small Cox Logo
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Help! Re: Glow Plug for the G-Mark 03

Post  gkamysz on Sun Mar 11, 2018 10:05 am

getback wrote:Greg , did you make bird cages for the Space Hopper??  Small Cox Logo

Still in design stage. I hope to offer various parts I design and make, not only Cox related. I realize this kind of stuff has been done before, so I'll try to make it unique somehow.
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Help! Re: Glow Plug for the G-Mark 03

Post  getback on Sun Mar 11, 2018 10:17 am

Sounds good and thanks again , Eric Babe Bee .049
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Help! Re: Glow Plug for the G-Mark 03

Post  Surfer_kris on Thu Mar 15, 2018 4:56 pm

I have been working on a new backplate for mine, the stock plastic tank is simply too soft for the vibrations that are produced by the engine. The threefold symmetry makes it a little tricky (or rather time consuming), but otherwise it is pretty straight forward. Below is the result, I made it slightly larger than the stock one inside the crank (this helps to reduce the dead crankcase volume a little), and used an o-ring seal rather than the very thin paper gasket that was on there before.



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Help! Re: Glow Plug for the G-Mark 03

Post  gkamysz on Thu Mar 15, 2018 5:37 pm

Kris, that looks nice! I haven't designed one yet. I may keep the trilobe theme, but not that big. Does that match the existing tank mount?
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Help! Re: Glow Plug for the G-Mark 03

Post  Surfer_kris on Thu Mar 15, 2018 5:50 pm

I made the mounting holes (or "foot-print") for the firewall the same size as the original (optional) non-tank mount. This is smaller than the foot-print of the tank mount, but could be made smaller still. I was thinking of using only two screws horizontally but finally went with the stock foot-print.

The two foot-prints are shown in the second page of the manual:
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Help! Re: Glow Plug for the G-Mark 03

Post  1/2A Nut on Thu Mar 15, 2018 8:49 pm

Great job as always Kris, if you make a aluminum carb body with a good fitting carb
the engine will for sure perform much better than stock. The backplate aluminum and
carb body aluminum will help wick away more heat. The engine runs very hot on the
bench and could do with cooling fins on the glow head. With all the above said the
potential heat reductions could be as much as a 25% improvement.

For those who don't own one here is what a stock G-Mark .030 sounds like:



AmpAbuser / 1/2A Nut
Published on Feb 6, 2016

G-Mark  .030 /Cox 4.5x2 /17.72k / 34mph / 5.64oz Thrust
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Help! Re: Glow Plug for the G-Mark 03

Post  Surfer_kris on Fri Mar 16, 2018 3:47 pm

It is an odd engine, don't know what to make of it.

Mine runs strong now, without the muffler I'm seeing around 21700rpm on the cox 4.5x2 prop and 10% nitro, but the throttle is pretty useless...

Perhaps it is all the SPI and the fact that the carb has no low end correction. It also runs hot to the touch but doesn't sag and the needle is not very sencitive (at a constant throttle setting). I tried shiming both the head and below the cylinder (head shims for the cox .049 are a nice fit) but it doesn't seem to help with the temperature or the throttling.

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Help! Re: Glow Plug for the G-Mark 03

Post  Surfer_kris on Sun Apr 15, 2018 2:00 pm

Well, now we just need a time machine, so that we can go back and bid on them too...? lol!

I have a few spare heads for mine, but I wanted to see if I could make a custom head that takes a turbo plug. In was not that difficult to make the parts, but even the hottest turbo plug from OS (the P3 one) seems a little colder compared to the stock plug. All out power is pretty similar but the stock head does not flame out as easily as the Turbo one near the "idle" at 10000-12000rpm...
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Help! Re: Glow Plug for the G-Mark 03

Post  coxaddict on Sun Apr 15, 2018 2:13 pm

What temperature is it running at? We used to use welding temp sticks that melted at different temperatures to approximate surface temps. Now there's laser equipped heat guns.
Running Nitro powered cars/trucks with large cooling heads with notches milled around the circumference increased the linear surface area increasing cooling as heat dissipates from the edges of the cooling fins.
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Help! Joy!

Post  MauricioB on Wed May 09, 2018 10:47 am

Thanks to the management of Mr. P. Ojeda I was able to access six units of Glow Plug for G-Mark .03
Now I am willing to try this engine !! Thumbs Up Thumbs Up Thumbs Up




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Help! Re: Glow Plug for the G-Mark 03

Post  ticomareado on Thu May 10, 2018 1:34 am

They are beautiful little pieces of fine machine work and I hope to find a sleeper example of one on the cheap one of these days at a swap meet or estate sale. Please advise though when somebody's bench test of one definitely beats a Tee Dee .020.
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Help! Re: Glow Plug for the G-Mark 03

Post  1/2A Nut on Thu May 10, 2018 2:43 am

Hi Tico, I have bench tested with the stock prop:



Published on Jan 20, 2018

G-Mark .030 stock prop 115Mx50M
Engine has  SPI. I removed the muffler / rare stock prop: 115M x 50M  / 4.53 x 1.97"
Static 17,280 Best Peak / 5.64oz thrust / .062hp / 46.3W / 66mph
Average: 16,818 per laser tachometer. New old stock engine was still a bit rich not quite holding a steady peak I would imagine best peak after some field flying around 17.4K  / 25% nitro / 20% castor. No effort was made to adjust for best low idle.
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Help! Re: Glow Plug for the G-Mark 03

Post  ticomareado on Thu May 10, 2018 10:14 am

This is a 1962 British test of Tee Dee .020. Note that prop selection was not very good on this test and it was a Limey test conducted with old tech measuring equipment and very questionable fuel. It's a mixed bag, but I suspect a Tee Dee .020 with that G mark stock prop will beat the .030 and might even equal it with a stock Cox throttle ring from a Pee Wee .020 and still have better throttling characteristics to boot.

http://sceptreflight.net/Model%20Engine%20Tests/Cox%20Tee%20Dee%20020.html
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Help! Re: Glow Plug for the G-Mark 03

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