Question for the Cracker builder

[jim_geib]

I have a question for you Cracker builders. I am making the piston and I ended up with 0.002 smaller than the bore. Is this going to be to loose?

Thank You
Jim geib

 

[vlmarshall]

It'll run! Add an oil groove or two to your piston, and think about making a displacement oiler, and you'll be quite happy... but it'll work like it is.
Post some pictures, there's no "Cracker Skunk Works"! ;D

 

[bearcar1]

there's no "Cracker Skunk Works"! ;D

Rof} Rof} Rof} Rof}

BC1
Jim

 

[shred]

I'd try it as-is. If it doesn't work well enough later on, put an o-ring groove in it and o-ring it.

 

[vlmarshall]

I'd try it as-is. If it doesn't work well enough later on, put an o-ring groove in it and o-ring it.

There ya go, the voice of experience. HIS is done. ;D

 

[jim_geib]

Thanks everyone, I am going to go with. If I have to make a new one I guess it doesn't matter when I make it.
This is what I have done sofar,

I wanted to wait and get a little farther alone before posting any photos. I am trying something a little different and adding a second cylinder on the other side. Don't know if it will work or not, but it is fun making the parts. I am making the piston out of stainless steel, this is the first time I have turned anything out of stainless and I just went a little to far.

Also what did you use for springs to hold the cylinder in place, did you start with a common spring, like from a ball point pen.

Thanks again everyone

Jim Geib

 

[vlmarshall]

Nice! I like the twin-cylinder idea, like the original Byers. I almost did the same, I would have cut the middle out of the footplate to make room for a long, but small-diameter, flywheel between the frames.

For the cylinder springs, I just dug through my spring bin until I found a pair that were suitable, mine are held in place with a nut, so I can adjust the tension a bit.



I know what you mean about photos; I waited a while myself. I can't compete with the modellers on here!

 

[bearcar1]

I'm likin' the twin idea. Day dreamed about doing that very same thing for a while but that's about as far as I got. I'll be watching, so not too many WTF's *knuppel2* :big:

BC1
Jim

 

[jim_geib]

Vernon,

I think I read somewhere on here that the cylinder should start to blow by the cylinder and the plate at about 25-30lbs, so that is what I was going to shot for.

I can only hope to for a project to look half as nice as the master work I see here, I look at what you'all have done and it gets me thinking that my work will get better. It is great to have someplace to pick the masters minds.

 

[vlmarshall]

I'm likin' the twin idea. Day dreamed about doing that very same thing for a while but that's about as far as I got.

Do it, Bearcar! Or go the other way, a single cylinder, double-acting Cracker. Reverse would be nice. If I ever repower one of mine I'll go that way.

Jim-Geib, the bit about wobblers blowing off the seat as a second safety seems to be a myth, several loco builders in the 16mm group have mentioned it, and something about an old commercial loco, possibly a Mamod, that started that rumor as a selling point. I guess it needs testing... not too difficult with a regulator.

 

[shred]

Looks interesting. If you offset the power strokes you may be able to get by without a flywheel; that would help a lot. IIRC one of the original 'Cricket's (a very similar design) was made with two cylinders and a bit of info on it is on the web.

 

[jim_geib]

Shred,

I was looking at the "Ideas" to build and did not like the overall look of it. the Cracker has more of the "Thomas The Tank Engine" look. I am going to quarter the the crank and hoope for a self starter. All the Cracker builds here has given me the inspration to give this a try, I am slow as I only get about one hour a night in the shop.

Jim

 

[bearcar1]

To carry the 'ideas' stage a bit further, and also to throw more fuel on the imagination fire, I had done some very rudimentary sketches of a twin Cracker engine in a 0-4-2 or a 0-6-2 configuration. ??? It would be a bit longer obviously th_confused0052 (yes, size DOES matter ;D) but would lend another dimension to the "interpretation" or variation of a theme to the model. Oh, isn't it fun to sit around and devise such contraptions? :big: A by product of having way too much available time on ones disposal.


BC1
Jim

 

[BMyers]

Very Cool. This engine sure is great for builder interpretation. I used a pen spring and socket head cap screw for my cylinder attachment.

 

[vlmarshall]

Very Cool. This engine sure is great for builder interpretation.

It sure is! I went through several ideas for modifications, before I realized that I'm going to be building a lot more locomotives... so I'll save the changes for those models. ;D

 

[itowbig]

im keeping my eye on this one. please keep posting pics of progress :bow: and thank you for showing us the pics :bow:

 

[jim_geib]

I finished the turning on the first rod, put two small groves in the piston end. Won't have to call it a ashtray(Bill Cosby)

Photo shows the stainless bolt I started with. If I'm lucky I'll get the turning on the second one done tomorrow night. Then I can setup the mill and do the conrod ends.

 

[vlmarshall]

Looks great so far, nice source of stainless steel!

Are they your own version of the plans I see?

 

[jim_geib]

I built it first in Autodesk Inventor first, or I guess I should say as I go along.


View attachment Cracker.bmp

View attachment Cracker.bmp