Model engines

[darryl]

Firstly, let me say that I appreciate all you engine builders, and the projects you come up with. My question is- and this is in no way critical of your projects- has anyone built an engine with high performance as a major criteria? I know some of you have worked with full size racing engines, but on a model scale it's only been manufacturers that have come out with 'pushing the limits' engines- at least from what I remember. You can buy them- 2 strokes, 4 strokes, nitro fuel, etc- but have any of you made one?

[sid pileski]

From my perspective, I like making steam, IC engines that have esthetic appeal, but that also run well.
High performance engines as you describe can be purchased by manufactures already. Let your wallet be your guide.

I also like the "monkey motion" of the things I build. That inherently means not pushing the envelope most likely.
But, given that, I guess pushing the envelope could mean super efficiency with steam or fuel(s).

My challenges are fit and finish for whatever I'm designing and building.

Sid

[darryl]

And you do some fine work, Sid. Art and function. The last 'engine' I built was before I left elementary school- and long lost as well. Mine was function and no art- it would run on my breath, but looked like crap. Should I take on an engine project today, it would probably be the same. Today I have the benefit of tools and machines, which would improve things- but still I don't think I would be making it beautiful. I'm of a different bend, I suppose. I wouldn't purposely make it ugly, but I seldom design a project with looks in mind. Different strokes.

In a partial answer to my own question, I did see a model of an Offy that looked good, and ran with authority to boot. I think what I'm missing is seeing the throttle response of a full size engine, but in a model. And again, I'm not knocking your engine, or any other- like Brian's engines. Just wondering if anyone has built their own for all-out performance.

[sid pileski]

To directly answer your question- I don't know of anyone specifically building for max performance.
I have seen on other sites, guys that race boats building for max performance.

Sid

[David Powell]

Hi, I only play with steam engines. I am disappointed if an engine does not perform well and will do a lot of work to improve the performance. Those I build myself run well and strongly but sometimes they do that at the expense of" Efficiency". Regards David Powell.

[DrMike]

I'll ask a similar, maybe related question, and with no disrespect whatsoever... what would it take to make a useful engine?

Let me explain....

I have various lawn and garden equipment - Stihl trimmer, chain saw, blower, Toro mower and snow blower, Craftsman edger - that have small engines that work amazingly well in fairly harsh conditions with minimal maintenance, both 2 and 4 stroke varieties. These engines seem no larger than the engines that are built here as models, but produce useful work year after year.

Is there a basic difference - materials, heat treatments, design, tolerances, construction - between these very common, hard-working engines and those built here as models?

I would very much like to build an engine, but have absolutely no interest in building one simply to put on a shelf as a trophy. I'm not sure at the moment what I'd power with it, but if I'm going to build an engine it has to have a purpose other than looking good and occasionally idling at a low rpm. How do I get there?

[Sparky_NY]

I'll ask a similar, maybe related question, and with no disrespect whatsoever... what would it take to make a useful engine?

Let me explain....

I have various lawn and garden equipment - Stihl trimmer, chain saw, blower, Toro mower and snow blower, Craftsman edger - that have small engines that work amazingly well in fairly harsh conditions with minimal maintenance, both 2 and 4 stroke varieties. These engines seem no larger than the engines that are built here as models, but produce useful work year after year.

Is there a basic difference - materials, heat treatments, design, tolerances, construction - between these very common, hard-working engines and those built here as models?

I would very much like to build an engine, but have absolutely no interest in building one simply to put on a shelf as a trophy. I'm not sure at the moment what I'd power with it, but if I'm going to build an engine it has to have a purpose other than looking good and occasionally idling at a low rpm. How do I get there?

The engines you cited are a LOT bigger than the ones seen built here. Pictures can be deceiving, the majority built here will fit in the palm of your hand. 3/4 inch bores are about the norm, one called "thumper" was around a inch. No doubt the stroke is also much smaller than the commercial engines cited resulting in a MUCH smaller displacement overall. Apples and oranges however, the engines built here on the forum are modeled more after old farm type engines that run at very low rpm.

Still, there is a lot of room for performance increases. Model airplane engines similar in size put out 1HP or more BUT rev much higher! Model airplane engines rev to 10-12K rpm as the norm. RPM's equate to power in this case. Those model engines however idle at rpm's quite a bit higher than the engines built here hit at their max rpm's.

To hot-rod the engines built here would mostly be a matter of design changes I would guess. Things that come to mind are increasing the compression ratio, rework the valves and guides for better flow (the valve stems fill most of the guide/port in the ones built here) and lastly camshaft design. Of course, fits and finish need to be addressed with much care as well.

[loose nut]

If you look through old Model Engineer magazines you will find quite a few "high Performance" model engines specifically built to drive something like a large model race car etc. As far as "useful" engines there is a reprinted book (Lindsay sold it) on building a 1/2 HP or larger gas engine that was designed for use on a farm or rural house. The whole point of building model engines is that they are NOT really useful for real world purposes, it is a hobby a way to escape the real world.,

[reggie_obe]

I would very much like to build an engine, but have absolutely no interest in building one simply to put on a shelf as a trophy. I'm not sure at the moment what I'd power with it, but if I'm going to build an engine it has to have a purpose other than looking good and occasionally idling at a low rpm. How do I get there?

Perhaps build a less than full sized Maytag engine?

https://classic-engines.com/engines-2/maytag/

[Rich Carlstedt]

If you want to produce peak performance, and use that as your objective, then you must have a Task.
Like build a better Weed Wacker motor, or a Silent Lawn Mower Engine
You can join a group like Boat Racers to compete against them or you can do a product not available and compete against yourself.
Your desire for improved Performance is an admirable goal. Model Builders have many similar goals such as improving one's skill level, or working in exact scale , or modeling something no one else has done--there are many individual goals in model work !
One big difference that should be noted.. when you take a "model" and modify it for a specific purpose, it is not longer a "Model"
Model are miniature replicas, or visual imitations of a engine and building a engine for a specific purpose ( or task) removes it from a model category.
For example , there are large models of the Aircraft engine -Merlin- used in a P51 and they are larger than a Weed wacker engine , but the Weed Wacker is not a model ! It is a performance engine with a task to power the Weed Wacker.
I hope the above explains the difference in the miniature engine field

As mentioned before by another poster, there are groups , like speed boat modelers , or car racer modelers who do race for fun,, but they are rare IMHO.
When I was a Kid, I modified stock model airplane engines for performance because I was in competition (1/2 A Speed) but did not have the skill to build a scratch built engine at that time
The big thing is.......Have Fun !

Rich

[Doozer]

I'll ask a similar, maybe related question, and with no disrespect whatsoever... what would it take to make a useful engine?

Let me explain....

I have various lawn and garden equipment - Stihl trimmer, chain saw, blower, Toro mower and snow blower, Craftsman edger - that have small engines that work amazingly well in fairly harsh conditions with minimal maintenance, both 2 and 4 stroke varieties. These engines seem no larger than the engines that are built here as models, but produce useful work year after year.

Is there a basic difference - materials, heat treatments, design, tolerances, construction - between these very common, hard-working engines and those built here as models?

I would very much like to build an engine, but have absolutely no interest in building one simply to put on a shelf as a trophy. I'm not sure at the moment what I'd power with it, but if I'm going to build an engine it has to have a purpose other than looking good and occasionally idling at a low rpm. How do I get there?

I am just shooting in the sky here,
but I think most home shop machinists
do not have the machines to make parts
to tight tolerance. Not a slam. Just a fact.
I have seen a few models at these engine
shows and those with pics posted here.
Lots of back yard methods. Real lack
of knowledge of machining and mechanical
design. All that is fine. You pee with the
wang that you brang. But to answer the
question of performance and efficiency?
It is all the things you mentioned in
Dr. Mike's post above. Dr. Mike said it
so hate on him. I reiterated it so hate on
me. I don't mind.
Take the brake cylinder reamer thread.
At work we make piston cylinders in
cast iron and aluminum. We finish ream
out cylinders with either a Dihart reamer
or a Maypal reamer. Yes a reamer.
They are not ground or honed, but the
surface finish is so fine, you might
think it was. These are very expensive
and high end reamers. Probably not
what you have ever seen. But we
turn out 1000 a day, sometimes more.
The piston to bore tolerance is .0002"
to .0004". To achieve that, the bore
size tolerance is half that. No joke.
We have machines to run these castings
and QC gauges to inspect these bores.
Air gages, Marposs gages, CMMs, the
whole works.
That is the difference. In production you
develop a method over years to get the
parts to the level of that engineering
and testing had determined what works.
The home shop money and mindset is
just not able to compare.
Now good work can be done in a home
shop. But it is the individuals intelligence
and experience that make top level work
possible. Not everyone is gifted or granted
with these on the same level. Fact of life.
Don't get offended. Face reality.
Even if it depresses you. And if it does,
ask yourself why you feel this way.
Maybe your ego will not allow you to accept
the answer, so you spew your own brew
of BS to yourself and other people as a
method to cope with your situation.
And this is the root of personal conflict.
Troubled individuals who can't own it.
Own who they are. And because of this
the rest of the world has to suffer them.
That is why some people have no friends.
And they grow more bitter, and the cycle
gets deeper. So it goes.
So it starts with being happy with one's self.
Something that is sometimes difficult because
of how some peoples parents treated them.
Many times the people who you love abuse
you, and the human brain can not comprehend
this. So you have angry and conflicted children
that become adults of the same caliber.
You can make a choice to treat the world like
your parents treated you, or realize what went
on, and make a choice to be the opposite.
And there you have it. The fork in the road to
being a well adjusted individual or being a
jerk that no one likes. Some people never
see it with clarity, so they plunder through life.
Hopefully we all walk the path that is best
for us.

-Doozer

[sid pileski]

Man Doozer!
So, what your saying is; if you design and machine like a hack, look in the mirror????

Sid

[Dan Dubeau]

That cut was very deep, and bound to cause some chatter.....

As to the original question....and Dr Mike's subsequent one, I'd love to see model engine powered tools, or other equipment. A scale v8 powered weed trimmer would be awesome. Would sure draw a crowd on Saturday morning trimming the lawn that's for sure. While I can personally appreciate the time and effort, as well as skill and patience that goes into making a running model engine that sits on a bench, I have no interest in doing so. I don't have that much free time to devote to something that will just sit there and do nothing but look pretty at this stage of my life. We all have different things that drive an motivate us.

I do love following the build thread and process. Seeing the various parts come to life along the way, and the finished product at the end is great, and I thank all you guys for posting them when you do.

[BCRider]

Over the years I've seen a number of fully made examples in magazines and even two full from scratch engines in person of custom built model projects. The ones done from scratch were in older vintage tether car engines that were all done by the owner's father and were raced for real back in the 50's. And I briefly saw a custom from scratch engine in a control line speed model back in the 70's at a contest I was at.

They end up being very functional looking and not really the stuff you see gracing model engineering magazines since the purpose of the engines was simply to make more power within the rules than the other options. The focus on the time making them being internal more than putting anything into the exterior. And of actually achieving an increase over what can be bought means that it is a lot of work over a number of development versions. So that's likely why it's not done very often compared to the "it just has to run and look good" examples.

Also folks that are looking for more power tend to produce "frankenengines" with custom internals inside commercially available crankcases. After all they are only after more power rather than worrying about a displayable model engineering exercise. And working with new internals in a stock case is one way to save a bucket load of machine hours.

An example of this is some local buddies that flew control line fast combat. One fellow did the machining and another the chrome plating to produce special pistons, liners and cylinder heads for use in Fox .36X combat model engines. These were very special made parts that gave the local team an extra thousand or so RPM and a precious couple of extra miles per hour during control line combat matches. The extra power led to breaking crankshafts at the inlet port in the shaft.... which led to my buddy making new crankshafts from better metal and with radiused corners in the openings to go with his new top end parts. But again all the many, MANY hours that went into producing a dozen or so sets of all these parts went into standard cases that left the engine looking essentially like a stock out of the box Fox engine other than for the cylinder heads.

[J Tiers]

Clearly home shops can produce very good parts and products. And do that with machines that are obviously sub-par. We've seen them here, and certainly in places like the Sherline museum.

The difference is that they are not going out the door at 1000 per day. Maybe 1 per week, more likely far less.

The other difference is technique and methods. When you want it very good, and you do not need it fast, there are all sorts of possibilities as to methods and techniques which are open to you even when the high production methods are not.

People made things decades ago with machines that make a round column mill look like a really good machine. Things like clocks that were accurate to 1 second per month, etc.

As usual, it is not the machine, but the operator. Don't like the result? Improve the operator.