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by davidll1984 Wed Jun 07, 2023 9:22 am
Cox Engine of The Month
Thermal Hopper Question.
Page 1 of 1
Canso07- Gold Member
- Posts : 104
Join date : 2016-12-12
Age : 42
Location : Calgary, Canada
Re: Thermal Hopper Question.
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.
Front end /crankcase is typical of most early cox engines. The front acorn nut has been ground down or damaged.
Cribbs74- Moderator
Posts : 11885
Join date : 2011-10-24
Age : 49
Location : Tuttle, OK
getback- Top Poster
Posts : 9556
Join date : 2013-01-18
Age : 65
Location : julian , NC
Re: Thermal Hopper Question.
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.
Thanks Canso07.
Canso07- Gold Member
- Posts : 104
Join date : 2016-12-12
Age : 42
Location : Calgary, Canada
Re: Thermal Hopper Question.
I think what you are seeing is just a casting flaw.
Cribbs74- Moderator
Posts : 11885
Join date : 2011-10-24
Age : 49
Location : Tuttle, OK
Re: Thermal Hopper Question.
I sent you a PM.
Cribbs74- Moderator
Posts : 11885
Join date : 2011-10-24
Age : 49
Location : Tuttle, OK
Thermal Hopper
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
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
Nicu.Pac- New Member
- Posts : 2
Join date : 2021-10-23
Re: Thermal Hopper Question.
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

getback- Top Poster
Posts : 9556
Join date : 2013-01-18
Age : 65
Location : julian , NC
Re: Thermal Hopper Question.
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
I will follow the auction course on ebay.
thanks
Nicu.Pac- New Member
- Posts : 2
Join date : 2021-10-23
Re: Thermal Hopper Question.
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?
GallopingGhostler- Top Poster
Posts : 4452
Join date : 2013-07-13
Age : 69
Location : Clovis, NM, USA
getback- Top Poster
Posts : 9556
Join date : 2013-01-18
Age : 65
Location : julian , NC
Re: Thermal Hopper Question.
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
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.
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
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.
GallopingGhostler- Top Poster
Posts : 4452
Join date : 2013-07-13
Age : 69
Location : Clovis, NM, USA
Re: Thermal Hopper Question.
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
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?

sosam117- Platinum Member
- Posts : 1060
Join date : 2016-03-23
Location : Suburb of Chicago, Illinois
Re: Thermal Hopper Question.
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
Although the later TH is still a fine specimen for a collector, personally, I am very happy

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
GallopingGhostler- Top Poster
Posts : 4452
Join date : 2013-07-13
Age : 69
Location : Clovis, NM, USA

» Two new in package Pre 1955 glow heads Space hopper/ Thermal hopper etc
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» Space Hopper .049/Thermal Hopper .049
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