Thermal Hopper - Cylinder Fin Reduction.

KIRK1950 Sat Feb 21, 2015 7:40 am

I just purchased my first Cox engine since 1963, an early Thermal Hopper 0.049. I build vintage speed planes and the engine will be going into a 1953 Magna Models 1/2A speed ship. As some may know, the Magna's are an all-magnesium fuselage/cowl & stab with aluminum-skin wings. The model will be for display because of the rarity.

I will need to reduce the outside diameter of the cylinder /head in order for it to fit inside the magnesium engine cowl.
Questions:
1) Is there a recommended minimum-diameter dimension for this procedure, in order to eliminate over-heating?
2) Other than gingerly chucking-up the cylinder in the lathe and hoping not to distort it, does someone have an easier, yet accurate method of doing this?

Thanks!
Kirk

getback Sat Feb 21, 2015 7:56 am

WELCOME TO THE FORUM KIRK !! I am not familiar with the plane I am sure others on here are But it looks like over heating is not a problem if your not running it ? and if the head is sticking out of the cowl can you install the cyl. after it is put together ? I have never cut one down myself though , but you will need to refinish it after or will bee steel flavored .

KIRK1950 Sat Feb 21, 2015 8:17 am

The display planes I build are flight-ready and built per the period. I had a hip operation 5 years ago, so I can no longer fly C/L.

The engine on the Magna 1/2A is totally enclosed, just like a large speed ship, aside from a tiny hole for battery lead and a 3/16" x 7/8" vent slot in the front and rear of the enclosed cowl.

JPvelo Sat Feb 21, 2015 3:30 pm

Welcome to the forum Kirk!
Here's something you might be interested in:

https://www.coxengineforum.com/t5898-cef-profile-scale-speed-rules

It's a profile scale speed contest we do on the forum. The last two have been reed valve only but this years contest added a Tee Dee class.
We would love to have your participation as a builder, proxy flying is permitted.

Here are the previous runnings results:

https://www.coxengineforum.com/t7730-reed-speed-2014-results?highlight=Results

https://www.coxengineforum.com/t6798-reed-speed-results?highlight=Results

And a link to the design/discussion page:

https://www.coxengineforum.com/t7115-cef-speed-contest-design-discussions

Hope you join in the fun!
Jim

Ken Cook Sat Feb 21, 2015 4:08 pm

Kirk, does the Peanut use the same engine? I believe on the instructions of the Peanut it tells you how to do what your asking. I could be totally incorrect about this but my flying partner does indeed have the Peanut kit. I would ask him but he's at a show currently in another state. Ken

GWILLIEFOX Sat Feb 21, 2015 4:15 pm

June 1957 Flying Models:
Thermal Hopper - Cylinder Fin Reduction. Fm570610

getback Sat Feb 21, 2015 4:22 pm

Man I know the feeling about the hip , I am sorry to hear that I have been needing one for a few years but can still deal with it for now .... the pain can really S.... Back To Topic

yes what Jim said ... I would think NO more than 1/2 on the fins reblue / black ? and come build / prois. s flight with use !! Eric Babe Bee

Repost

getback Sat Feb 21, 2015 4:26 pm

KIRK1950 wrote:I just purchased my first Cox engine since 1963, an early Thermal Hopper 0.049. I build vintage speed planes and the engine will be going into a 1953 Magna Models 1/2A speed ship. As some may know, the Magna's are an all-magnesium fuselage/cowl & stab with aluminum-skin wings. The model will be for display because of the rarity.

I will need to reduce the outside diameter of the cylinder /head in order for it to fit inside the magnesium engine cowl.
Questions:
1) Is there a recommended minimum-diameter dimension for this procedure, in order to eliminate over-heating?
2) Other than gingerly chucking-up the cylinder in the lathe and hoping not to distort it, does someone have an easier, yet accurate method of doing this?

Thanks!
Kirk

.........Is it just the GLOW PLUG you are wanting to reduce ?????

**Admin** Sat Feb 21, 2015 4:39 pm

Welcome to the forum!

Are you planning on turning the fins off like on this Tee Dee?

Thermal Hopper - Cylinder Fin Reduction. Jason_10

Customized TD .049

If the cylinder uses a small diameter head, you may want to consider using an early #2 cylinder (as used on early Babe Bees). Finding replacement heads (if the engine is ever put into use) would be much easier and plus you could preserve the original parts if needed for other projects. In Feb of 1956, Cox switched over from the small dia. heads to the current heads.

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