Goin' Crackers.

[vlmarshall]

Shred's build of the Cracker (April's Project Of The Month winner) has convinced me to build my own. I haven't wanted to start a thread on it, mainly because of the craftsmanship standards that I see on here. :bow:
Still, here's my progress so far.
The first thing I had to do was come up with the gears, as the pitch diameter would set the axle and crankshaft spacing. I followed Shred's advice, and used RC pinion gears from Robinson Racing, as I've used their products many times in my younger days.

For a lot of this build, I'm "cheating" and using a CNC Sherline mill at home, and a manual Hardinge lathe at work. Cutting out the side frames was simple enough, and I decided to build TWO locomotives, one for myself, and one for my dad.

Here's the first one being cut out on my little Sherline at home.

This is too easy, so far. The loco frames are 10mm longer, 5mm added to each end, to make room for a slightly longer boiler, and more room on the footplate as well. Originally I was going to add all 10mm to one end, and move the fuel tank under the footplate and between the frame rails, as I've read elsewhere online, but decided against it, at least for THIS build. ;D

I turned two sets of bushings, again diverting from the plans, and making all 8 bushings to the same dimensions.
Here they are in place.

 

[vlmarshall]

After reading a boiler post on here today, I wonder if I should have made my boiler end plates differently. The thread I saw today showed NO radius in the corner.
When I made my first set the radius I used was way too big...but at least it'll add extra water capacity. I'll use the big ends for the boiler backheads, but I turned a smaller radius on my mandrel, and made a second set.
Sorry for the blurry photo, the rest will be better. ;D

 

[vlmarshall]

The wheels were fun, so I made an extra set. I enjoyed the two angles, and by setting the tool to cut one angle, and the compound slide to move along the other, these were quick and easy...especially since I turned them from 12L.

I added a .200" boss to the back side, so I could use 4-40 setscrews to secure them to the axle. The only place I want to use Locktite on these locos is between the crank throw and the crankshaft.


The frame end beams were easy, and mostly featureless for now, other than a few holes.

 

[vlmarshall]

For the smokeboxes, I decided that using a pipe cap, with it's radius, would help give the Cracker a smaller, yard-loco appearance.

Here are both pipe caps, with a hole in one end for the smokebox doors.

They look more like engine cowlings for a radial. ;D

 

[vlmarshall]

The pistons were easy enough, but I made them .375" instead of the plan's .3149".

 

[vlmarshall]

Yesterday I made the cylinder backplates, and some quick-and-dirty banjo fittings, that need some more work before I'm happy with them.

Those giant hex nuts, and the locomotive's button-head Allen screws, are going to be really unpopular around here. ;D

 

[Shopguy]

Looking good, coming along real nice.
Don't worry too much about the screw heads at this point, get the loco running, you can fancy up the fasteners later.
Regards
Ernie J.

 

[shred]

Looks great... better than mine at the time ;D

My boiler plates have rounded corners, though not that much. I don't think it matters a lot at these sorts of pressures. According to one place, you could even use flat disks of copper, though I'd rather have the silver solder contact area of flanged end plates.

As I read elsewhere "It's a little unfair to a tiny model to show a big photograph of it..." I found 2-56 button-head cap screws looked enough like rivets when viewed normal size that's what I mostly used.

 

[tel]

Nice start! :bow: One of these days I'm going to 'crack' and build one meself.

 

[itowbig]

alright nice work i want to build one for the wify. but its going to have to wait im not that good yet.
yours is looking real nice. thank you for showing us the build.

 

[vlmarshall]

Thank you all for the encouraging comments, and Shred for the tips. The people here make an enjoyable project even more fun.
My newest progress is a few more pieces;
The boiler bushings, made from Phosphur Bronze...I made them all the same size instead of the plan's 10mm/8mm, tapping them all 5/16-24.

Cylinders for both machines... they're a bit bulky compared to some of the others I've seen. As I mentioned earlier, with the piston photo, I've enlarged the bore from the plan's .3125" up to .375". I just couldn't help myself. ;D

I wanted plenty of material at the contact face for future lapping, both of these locos are going to be runners, I'm planning for wear. I added brass bushings to the big-end of the pistons for the same reason.

...and a pair of flywheels. One of 'em is a day or two older than the other. ;D

I made them thicker than the plan (like everything else). I'm trying to get these engines to run as slowly as I can, and figured the extra mass couldn't hurt. Besides, the thicker flywheel offsets the look (and balance) of the cylinder hanging off the other side. ;D


Once again, I'm really happy with my little Sherline mill.

Thanks again to everyone for the comments. This is fun, I should have started sooner. ;D :bow:

 

[zeeprogrammer]

This is fun, I should have started sooner.

I have had that thought every day since Feb 12 when I started this great hobby.

It is fun and I was fortunate (as you) to find this site.

 

[vlmarshall]

:big: Test ran both engines on air today...no direct connection available, so I just used an airgun. One of them runs a LOT slower than the other, I've got more work to do. No new photos to post, yet.

 

[zeeprogrammer]

A test run and no pics? What are you thinking?
Can't wait to see.

 

[vlmarshall]

A test run and no pics? What are you thinking?
Can't wait to see.

I was at work! ;D Lunch break, using the only non-OSHA-compliant air nozzle in the place, fighting a coily air line, while trying to hold a loco frame without being eaten by gears.

I'll post a VIDEO when I cobble together a better test setup. I know I have a low-pressure regulator around here somewhere...

 

[zeeprogrammer]

I was at work! ;D Lunch break, using the only non-OSHA-compliant air nozzle in the place, fighting a coily air line, while trying to hold a loco frame without being eaten by gears.

Oh hey I understand. Really I do. I was just worried about what everyone else thought. Tough crowd here. (At work...yeah right.) :big:

Myself...I'm on HMEM nearly every day at lunch. Even when I'm Skyping with wife (don't no one tell her). Can't work on the engine though. She'd see me.

 

[BMyers]

The first thing I had to do was come up with the gears, as the pitch diameter would set the axle and crankshaft spacing. I followed Shred's advice, and used RC pinion gears from Robinson Racing, as I've used their products many times in my younger days.

Very Nice Job !

Does Robinson Racing have a web sight ? What are the P/N's of the gears ? This engine is on my list of projects.
First objective find a lathe to replace my monster P&W (see show off your lathe link)...

 

[shred]

Very Nice Job !

Does Robinson Racing have a web sight ? What are the P/N's of the gears ? This engine is on my list of projects.
First objective find a lathe to replace my monster P&W (see show off your lathe link)...

These are what I used: http://www.robinsonracing.com/catalog/48pitchpinion.html
The smallest and largest the hobby store had in 48P-- 12T and 35T. I suspect that being off a tooth or two either direction won't hurt as long as you get the axles located correctly. Interestingly the combination I arrived at almost completely by random is very close to the "original" full size Byers locomotive.

 

[vlmarshall]

Very Nice Job !

Does Robinson Racing have a web sight ? What are the P/N's of the gears ? This engine is on my list of projects.
First objective find a lathe to replace my monster P&W (see show off your lathe link)...

I used the same Robinson link that Shred used, and bought 41 and 12-tooth gears, running them on .125" shafts cut from drill blank. Smooth and straight stuff.
Anyway, I just meshed the gears and measured the spacing, although some people might find Marv Klotz's "GearSpur" utility more useful. http://www.myvirtualnetwork.com/mklotz/

As it was, I ended up running in the gears with lapping compound to get them free-running enough to spin over a few revolutions with a finger flip. I was going to check the profile on a comparator first, ( I suspect the profiles aren't exactly correct... it couldn't have been MY error. ;D : ) but I didn't get around to it before the lapping compound.


Interesting PW lathe, that IS a monster. I really like the looks of that little South Bend you've got... the first lathe I ran was an old open-belt head like that, and I've had a soft spot for them ever since.

Thanks for the compliment on the Crackers! I hope to have a photo update soon, but the little things I've been doing lately aren't very interesting.

I do have a question for Shred; What is the ID of the steam lines you used? The stuff I have is mostly .062", although i have some thinwall K&S stuff that's .097". If I have to, I'll make a line of each size, and try them both.

 

[shred]

I used the same Robinson link that Shred used, and bought 41 and 12-tooth gears, running them on .125" shafts cut from drill blank. Smooth and straight stuff.
Anyway, I just meshed the gears and measured the spacing, although some people might find Marv Klotz's "GearSpur" utility more useful. http://www.myvirtualnetwork.com/mklotz/

As it was, I ended up running in the gears with lapping compound to get them free-running enough to spin over a few revolutions with a finger flip. I was going to check the profile on a comparator first, ( I suspect the profiles aren't exactly correct... it couldn't have been MY error. ;D : ) but I didn't get around to it before the lapping compound.

I ran into a problem where I didn't leave enough play in the gear train when laying it out. I doubt these little guys are perfectly to spec either. Highly recommend computing the correct axle spacing.

I do have a question for Shred; What is the ID of the steam lines you used? The stuff I have is mostly .062", although i have some thinwall K&S stuff that's .097". If I have to, I'll make a line of each size, and try them both.

I don't remember the IDs. It was K&S copper tubing, and a quick slap with the calipers on the steam-dome-to-engine line shows it to be 3/32" OD, with the exhaust from engine-to-stack being 1/8" OD-- performance improved with the larger exhaust pipe but I never tried larger on the incoming line-- the engine port sizes will limit flow, so I'd guess anything somewhat larger than the ports will be ok.

[update: the 3/32" stuff appears to be pretty close to 1/16" ID, and the 1/8" is probably close to 3/32" ID]