Rider-Ericsson 1/4 scale 2nd Time Around

[Bobsmodels]

Hi All

I decided to start a new thread on this topic rather than tack it on  Bill’s fine thread, which motivated me to build this model.   I  always try and find out every bit of information from other builders when I start a model and enjoy all the fine build articles so I hope adding this one will be of use to potential builders.   A lot of my setups are going to be different only because I choose to do them that way,  for the newbies—there is no “right way” it just depends on the machines you have.   Once the machine is picked then the “way” follows good practice on that machine.    Another question that gets asked often is “how long did it take? “, I will provide that for the build.  Of course the time I spend is based on my skill with the machines and my process for setup, checking drawings, etc.   Along the way I  will share my boo—boo’s, any special jigs when as needed,  and “others” which are usually things I should have made in the past to make the shop more useful.

The model was purchased at NAMES in 1992, so the castings are well aged!  This model was “started” 11/15/2013, which was the day I decided to do it rather than a 1/4 scale Stove Pipe Domestic.   After some interactions on the net I placed orders for materials on 12/16/2013.  I spent about 10 or so hours just planning and looking over the prints.   I also decided to spend time doing this build article.

I have no timeframe for the model, it will be done when it is done.  I am retired and spend most of my time in the shop.  I like to experiment a bit so there will be some side trips that are not necessary for building the model, I just may wish to try something different.   Again for the newbies there are many ways to go, the point is to enjoy yourself, learn something new, and end up with a model you built!    I encourage all the folks out there who hesitate to start, to just go ahead and  make chips.  My scrap pile is large with many “learning's”.  My granddaughters, when they were 8 and 10 made a “Finger Engine”, then a small oscillating steam engine each (you can see a picture of them in Model Engine Builder issue 25 under Readers Engines).  This summer they  are working on a Sterling engine—which was another reason for grandpa to build this one, don’t want them to get ahead of me!

Just a note, I will try and respond my best to questions.  I am not on line everyday so I am not ignoring anyone.   Not sure how others write these but I got a bit of the model finished before I started this thread. 

Bob

[fcheslop]

Hi Bob, good luck with the build its an engine I would love to build one day.The castings over here cost a kings ransom so my version will be bar stock been a tight wads.
Looking forward to the adventure.
cheers

[b.lindsey]

Looking forward to the adventure.

Me too!!  Me too!! Really looking forward to it Bob.

Bill

[zeeprogrammer]

Looking forward to the build and the stories that accompany!

[Don1966]

Bob, like the rest eager to see this one built.

Don

[Kim]

Hi Bob,
I looking forward to following your build! This engine is on my short list. I'm excited to see your progress.
Thanks,
Kim

[Bobsmodels]

Hi—just a few more preliminaries then off to building and photos

Bob
 

Material Choices and Design Changes

This is my first attempt at a Stirling Cycle engine.  Based on discussions with modelers who have built a number of these and others, as well as reading threads here and elsewhere I decided on a number of changes to the materials for the 1/4 Scale Rider Ericsson model.   One source for the changes is fellow modeler, Brad Smith,  who sold several kits years ago which are currently unavailable.  Brad wrote an article for Gas Engine Magazine in October 1988.  I am using most of his suggestions in that article.  I also spoke with him on several other issues to understand better some build specifics as related to Stirling Cycle engines.  As of now I am planning Stainless for the cylinders, copper for the bottom of the hot tube, stainless for all the bolts, use of a grill cleaning block for the displacer piston, using ball bearings rather than needle bearings, and all the rest of the bearing surfaces will be Oilite bearings.  One emphasis that was repeated by others was reducing friction.  During construction I may change my mind, point is to lay out a plan and go forward.

As a start in modifying the design I decided to remove the lip from around the casting, as pictures I see of 8 inch all have a non-lip base.  I also removed all the casting lettering associated with Keeley.   Next, as mentioned in Bill’s thread,  I noted that there were some issues with the furnace fit.  Since the drawings I have assumed a sheet metal furnace the OD of the displacer cylinder flange does not fit in the aluminum casting furnace.  I also wondered why the two bolt hole patterns for the two cylinders – 8 bolts on top and 6 bolts on the bottom.  These two bolt patterns seem like a lot of work.   I looked at photos of the full size and it appears they used eight bolts and that the same bolts were used to secure the two cylinders, gasket, and base all as a sandwich.  I also asked some questions on the Hot Air Engines (SMOKSTAK) site and they confirmed my observation.  I am not sure why the model is not made the same way. 

In order to confirm a working redesign, I modeled those parts (base, cylinder, displacer cylinder, gasket, and furnace) in my 3D CAD system – Alibre.  I made them all up with the same bolt pattern as the main cylinder flange.   I ended up with a slightly different bolt hole diameter.  I also took the furnace and bored a diameter slightly larger than the displacer cylinder flange which then fit nice in the furnace.  Using the assembly feature in Alibre I put them all together and they fit well.  When I machine each part I will see if it really works, although I have found if I start with the actual casting dimensions in the Alibre model everything seems to work OK.  I learned this when I modeled the 1/8 scale Galloway completely.   I will supply drawings as I get to each section so others can see what I did.  I spent 11 hours on the modeling. 
So I will now have at it and see where this all goes.


Bob

[fcheslop]

Hi Bob, is this the one in the Steam and Stirling book1 or2, just so I can follow along.
Have you seen Jerry Howells comments on the hot end  about a groove to help reduce heat transfer ? Iv not tried it yet.
I had thought of using ball bearings through out to reduce friction and my current long term build has a total of 20 ball bearing the whole lot just glides compared to the original Wiggers design.
I like to use Graphite for the power piston and use good quality as some of the cheaper stuff is very gritty/crumbly to say the least or a good close grained cast iron for both the cylinder and piston.
Roughly what are the dimensions for the base casting as theres no size in the book I have.
Cheers

[b.lindsey]

Sounds good to me Bob, I think you are wise to take your time and plan things out as you are doing. Looking forward to seeing some chips being made but only once you feel confident in doing so

Bill

[Dave Otto]

HI Bob

When I built my Essex hot air fan I also modified a couple of the castings and the shape of the blades based on a picture of an original fan that I had. These were also castings the came form the Keeley engine works patterns (Now Myers Model Engine Works). I also removed all the lettering that didn't belong and modified the cylinder casting to look more like the original in the photo.

Not making the hot end completely from copper is a good plan; my buddy made his from all copper (because that is what the print called out) and eventually re-made it from steel with a copper cap. He also turned a waist (ala Jerry Howell) near the top to slow the heat transfer. The all copper hot end transferred heat so well the engine required a large flame to make it run. The steel hot end with a copper cap made a whole new engine out of it.

Ball bearings were also used in place of the needle bearings.

I have a set of the original Keeley castings aging on the shelf; this is the one with the fabricated fire box. I have often wondered if maybe I should purchase a cast fire box if Myers has them available.

It appears that you are off to a great start and I will be watching for updates on your build.

Dave

[Bobsmodels]

This is the same engine as in Steam and Stirling the first book.   The base demensions are about 8.312  x 3.875.   
I am going to make some kind of heat "dam" ie a groove.  My wall thickness is.065, another approach would be
to turn it down to about .030.  Stainless was my choice as it is not the best heat conductor.
As to the piston of cast iron, one thing fellow builders mentioned is weight and friction is the enemy of these engines.
So my choice for the displacer piston of the grill block almost no weight, and aluminum for the piston again
light weight.  As for using graphite I had not considered that as I am not familar with its machining properties
and strength characteristics for a piston with the configuration in this engine.

Bob

[Bobsmodels]

Here we go!

Started by cleaning up castings, it took about 5 hours.  After all the castings were cleaned up they were bead blasted to a nice consistent surface and to clean out any remaining mold sand.    The photo shows all the castings ready to get a coat of aluminum primer.  I use a NAPCO 7222 product with zinc chromate in it.  The photo also shows some brass castings for the linkages that Paul Jacobs sold.  I bought them in 1993 according to sales sheet in the bag with them.  The Grill-Brick is also shown that will be used for the displacer piston. In addition, you can see the two stainless tubes to be used for the cylinder sleeve and the displacer hot tube cylinder.   The last several models I built did not get any paint until the model was running.  I decided to prime the Aluminum castings this time.   

[Jo]

  Nice looking castings 

Jo

[fcheslop]

Hi Bob , Thanks for the info. I dont think graphite would be suitable for this engine.It machines easily and can take a thread but I prefer to use two pack glue and fit inserts.Iv used it for linear no load bearings to good effect.
I have not come across the barbecue block so will keep an eye open for some as Im always on the look out for engine materials
Best wishes

[tvoght]

The choice of the grill cleaning brick for the displacer is interesting. A search shows it to be pumice stone. The adjectives "light-weight" and "non-porous" also appeared.

Any idea how it will machine? I'll be watching with interest.

--Tim