Thermal Hopper Question.

Canso07 Tue Jan 19, 2021 10:27 pm

Hello everyone,

I was wondering if anyone could tell me if this is a real Thermal Hopper? or any information.

Thanks in advance.

**Cribbs74** Tue Jan 19, 2021 10:50 pm

Head looks correct as does backplate, externally the cylinder looks correct. Should be dual bypass, tapered grind with SPI.

Front end /crankcase is typical of most early cox engines. The front acorn nut has been ground down or damaged.

getback Wed Jan 20, 2021 5:25 am

Some reference https://en.wikipedia.org/wiki/Cox_model_engine#Early_engines and http://www.mh-aerotools.de/airfoils/index_centerframe.htm Very Happy

Canso07 Wed Jan 20, 2021 11:28 pm

Thanks Cribbs, it looked legit to me as well but wasn't to sure about the ridges on the side of the crankcase next to the backplate. I did purchase it so have to wait to inspect it more.

Thanks Canso07.

**Cribbs74** Thu Jan 21, 2021 10:39 am

I think what you are seeing is just a casting flaw.

**Cribbs74** Sun Jan 24, 2021 3:03 pm

I sent you a PM.

Nicu.Pac Sat Oct 23, 2021 7:14 am

Hello everyone,

my name is Nicu, I am from Romania and I am glad to be part of this forum.
I have a limited collection of cox engines at the moment, but I want to expand it. At the moment I am looking for a Thermal Hopper, if anyone has one for sale, I would be happy to discuss a sale price.

I look forward to relying on your support

Nicu

getback Sat Oct 23, 2021 7:37 am

Hello Nico !! Welcome to the Forum ! This is in my option a good /reasonable deal Free shipping Worldwide ! >> https://www.rcgroups.com/forums/showthread.php?1910064-Rare-cox-thermal-hopper-nip%21%21 And then there is https://www.ebay.com/itm/393642672616?hash=item5ba6ee81e8:g:8M8AAOSwv11hchQF This Site Rocks!

Nicu.Pac Sat Oct 23, 2021 8:32 am

thanks for the answer, the first option is much too expensive for me, I would like to fit in a maximum of $ 90.
I will follow the auction course on ebay.

thanks

GallopingGhostler Sat Apr 15, 2023 10:54 am

This is interesting. My Thermal Hopper is a pre 1956 engine, has very generous dual bypass ports but no SPI. Perhaps the later TH's had an SPI cylinder?

getback Sun Apr 16, 2023 10:25 am

mine seems to be a later version it has to look like the original head and SPI I think I got my cage from the same guy you got yours from he seems the only make a few of the year

GallopingGhostler Sun Apr 16, 2023 5:05 pm

Eric, in my other thread:

https://www.coxengineforum.com/t17211-cox-049-thermal-hopper-a-never-ending-story

I posted Mark Boesen's illustrated photo, so you can know whether you have the earlier or later Thermal Hopper:

From: https://www.coxengineforum.com/t11650-a-thermal-hopper-story-thanks-levent-suberk#148519

Mark Boesen on Mar 06, 2018 wrote:

Mine matches the cylinder on the right, because the outer cylinder wall before the cooling fins is stepped. Also interesting is it does not have SPI.

If yours is like the left, then you have the later. Regarding glow heads, if your cylinder can use the current heads, then yours is the later 1956+ model. Regarding glow heads, yours is even different than mine. Mine looks like the current Cox ones, but the fins are slightly thicker and the smaller aluminum head pin rim has a ridge around the middle of it. if I want to use a glow plug adapter head would require either redrilling out and retapping with a 1/4-32 tap or a special adapter head.

I don't know if my TH crankcase is threaded same as yours and could replace with a current cylinder and piston.

sosam117 Mon Apr 17, 2023 7:04 pm

GallopingGhostler wrote:Eric, in my other thread:

https://www.coxengineforum.com/t17211-cox-049-thermal-hopper-a-never-ending-story

I posted Mark Boesen's illustrated photo, so you can know whether you have the earlier or later Thermal Hopper:

From: https://www.coxengineforum.com/t11650-a-thermal-hopper-story-thanks-levent-suberk#148519
Mark Boesen on Mar 06, 2018 wrote:

Mine matches the cylinder on the right, because the outer cylinder wall before the cooling fins is stepped. Also interesting is it does not have SPI.

If yours is like the left, then you have the later. Regarding glow heads, if your cylinder can use the current heads, then yours is the later 1956+ model. Regarding glow heads, yours is even different than mine. Mine looks like the current Cox ones, but the fins are slightly thicker and the smaller aluminum head pin rim has a ridge around the middle of it. if I want to use a glow plug adapter head would require either redrilling out and retapping with a 1/4-32 tap or a special adapter head.

I don't know if my TH crankcase is threaded same as yours and could replace with a current cylinder and piston.

Took a good close-up of my Thermal Hopper's cylinder/piston and it seems to be pre-1956?

GallopingGhostler Mon Apr 17, 2023 10:25 pm

sosam117, based on @Mark Boesen's annotated photo, it does certainly appear that you have the earlier to 1955 version Thermal Hopper, also no SPI? Then congrats.

Although the later TH is still a fine specimen for a collector, personally, I am very happy

that I have the earlier one, because it is just that more unique. I'll find out later, but according to an earlier review, it was definitely a performer.

According to Aug. 1955 Model Aircraft Magazine, on 25% nitro 25% All Castor oil fuel, it put out 0.066 BHP at 17,200 RPM, well within the Babe Bee / Golden Bee limits, paralleling that of the QZ, forerunner to the Sure Starts.
http://sceptreflight.com/Model%20Engine%20Tests/Cox%20Thermal-Hopper%20%282%29.html

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