MadModder

 

 

 

 

 

DIY Homemade Rat Steam Engine No.2

It’s the school holidays down here in Oz and we also had a recent Long Weekend (yes we’re the land of the Long Weekend here) and myself and my 13 y.o Grandson made RAT ENGINE #2. (RAT ENGINE #1 we made some time ago).I put out a call if anyone had some Mamod parts laying around and my friend Walter over Western Australia answered the call.

We had to make a new brass piston as the original was very worn. RAT ENGINE #2 is made out of 2” copper plumbers’ pipe and 2” copper end caps. One of the end caps we turned down in the lathe so that it sat on the burner part of 2” copper pipe and that was silver brazed on.

The Mamod engine bracket was copper riveted on and then silver brazed on the inside of the pipe over the copper rivet and a touch of silver braze on the outside.

The ˝” chimney stack we did something new, and silver brazed in some copper pipe cross sections (really made a difference to boil times).

Made up brass (yes only from brass) bushings for the safety valve and for the water level plug and tapped the safety valve bushing for a Jensen safety valve and the water level plug 6mm and turned up the water level plug out of some scrap brass. We had some fun lighting a fire under the boiler with some gumtree cut up branches and leaves mixed in with a fire starter to test the boiler for leaks with only the safety valve installed.

The chimney stack is silver brazed into the firebox and we did that on our brick hearth….the rest of boiler was soft soldered together. Also, silver brazed up the gas burner.

Turned the chimney cowl on the metal lathe from some scrap.

Brazed three (3) copper feet onto copper burner section of the boiler. Needed to turn up some brass risers under the feet for the gas burner to work better.

There are some brass risers under the 5mm steel plate to help keep the heat off the routed timber plinth.

Bent and soft soldered in the K&S copper piping and made a copper bucket (silver soldered) for the condensate and soft soldered on a small copper spike on the copper pipe for it to swing on.

Cut the 5mm mild steel plate on the bandsaw and drilled and tapped it for the brass bolts.

Pickled the boiler in a strong Citric Acid solution.

 All in all it was a GREAT time together, could it have been built better? Yes, but then my 13 y.o Grandson wouldn’t have had the fun and lessons of using all those tools and techniques. Instead of just watching, he was hands on building it.

We had some fun hours now the last couple of days steaming this together.


 

 

 

 

 

 

 

Nice work 

I wonder if you could use cheap angle grinder bevel gears ? 

I am fascinated with RC construction equipment.  Being a cheapskate somewhat frugal, I cannot justify paying way more for something I can play with, than I paid for my first car/s.  I don 't have the skills/talent to be able scratch-build, but I can kit-bash pretty well. (And I've got a couple of 3D printers.)  With that in mind I set about collecting Bruder construction toys for RC conversion, as retirement projects.  Why Bruder toys?  They're all 1/16 scale, reasonably accurate to scale, almost indestructible, and sorta cheap - at least when compared to their 1/14 scale cousins.  I have a set of shelves in the basement that would be the envy of many a kid.  Retirement arrived at the end of last month, so it's time to set things in motion.

In true MadModder tradition I decided to see what I could Frankenstein together from cheap Chinese clones of other RC car/truck parts.  I have 4-5 Bruder trucks, that will ALL require front axles, center differentials, rear differentials, wheels and tires.  I knew that the differentials would be a major road block.  I looked at what was available, drooled all over my chin because of the detail, then said - no flippin way am I paying $200 per axle.  I found a 1/12 scale Kong rear diff that looked like it MIGHT work.  Ebay to the rescue and for $40 I had one in my hands.  It would work, but only as the rear axle, as a center diff they are un-obtainium.  Thusly the Frankendiff was born.  I decided to start with a 1/10 scale crawler rear axle from WPL.  Why that axle?  Well they're cheap, about $20, and "mick thebass" used them in his RC conversion of Bruder's Ausa dumper.  I started 3D modeling an axle housing for the WPL axle that would at least sorta resemble the Kong axle.  This was the first working version, it only took 9-10 tries to get to this point.


Yeah, I know, it sorta looks like something you could build with Tinker-toys.  That led to this version:

At least it looks less like a Tinker-toy construction and more like the Kong axle - doesn't actually work though.  Although, neither do the WPL axles when you first get them.

This is the first version that actually works, almost correctly.  It still binds a little at one point, but I think that's in the spider gears.  The next image shows the metal Kong axle, my axle, and SOME of the various failures.  I took the rear cover off my axle to show a correction I had to make to the housing.  I had to create a place to add 2 more screws to hold the housing halves together.  The actual rear cover is the one with the shiny bit in the second row, (the shiny bit is the drain plug.)  Up in the upper RH corner is my first, and last, attempt at a 3 part front wheel - hub, wheel, and hub cover.  Those M2 screws are just too fiddly to install while trying to line up those itty-bitty holes in 3 parts.  You need a lot less hands when the wheel and hub are 1 piece.

This takes care of the differentials.  The center diff is the same as the rear diff, it's just got a pinion housing on both the front and rear halves of the diff.  I still need to shorten the axle shafts, re-dill for the drive  pins, and re-thread the ends M4.

I've already shown you the front wheels, on to the rear wheels.

The doo-dad on the right is the locknut cover, the screws that hold it on will simulate the lug nuts.  On each side of the wheel are parts that failed for one reason or another.  This wheel is actually also a failure, the gap between the tires was too wide.  The wheels in the next picture are also failures.  These measure 200mm from outside to outside.  I need to be at around 185mm, so I need to find a place where I can take 7-8mm out of each side.  I can take another 2mm out of the gap between the tires, and change the wheel offset by 5mm-ish and that should get me close enough.


The tires are Lesu 1/16 scale "narrow" tires, they're fairly cheap - about $15 a pair.  They are also close to the OD of the Bruder tires, about 2-3mm smaller and I can live with that.  The 1/14 scale tires are about 10-15mm larger, and cost significantly more.  I've only got 2 of the "narrow" tires now.  I've got 2 of the Lesu "wide" tires too, but they are only about 1-2mm wider, cost about $5 more a pair, and take a different wheel profile.  Nope, gonna stick with the the narrow tires for now, thank-you-very-much.

Don

Unlucky Jim! I have this problem on occasion, it is no fun at all!
Hope you feel better soon!
Phil