Machining...Logical Starting Place for an Engine Build

[BronxFigs]

Drawings have arrived....now what?

After assembling all that's needed, metals, tools, etc, what would be the logical place to start the machining process. Crank, pistons/cylinders, crankcase? What's the most efficient way to build an engine? What parts would you make first?

In my way of thinking, the pistons/cylinder assemblies, camshafts, are probably critical. However, the crank, crankcase, and a few other things can be machined, and tweaked to fit the other parts if there is a screw-up. Of course, I would strive for accuracy, but there might be a way to save re-making a few parts if you approach the build in a logical manner.

I know there is a sequence to follow when machining an individual part, but I haven't read very much about the building of an engine in respect to WHERE the logical starting point might be. All engines have parts in common...so, how do you guys approach a new project?

You can't learn if you don't ask...so......I'm curious.



Frank

 

[Jasonb]

If I'm not mistaken this will be your first engine build in which case I would suggest rather than follow the more usual route that you get some of the small parts made that are not too critical or dependant on other parts to get their fits.

This will allow you to get used to working to the drawing tollerances and generally get you into the swing of things before tackling more critical parts.

I still quiet often take this approach as one engine is being test run, stripped and painted to feed my desire to machine something I just pick odd little items off the drawing that can be knocked out quickly in the odd spare moment. This also has the benifit of making teh engien come to gether quicker in the end as all the littel fiddly bits are ready to assemble as the large items are completed.

Normal approach for a small 4 stroke aero type engien would be would be something like

Crankcase
Cylinder
Head
crank
bearings
piston (& liner if needed)
conrod
Valves, rockers, pushrods
Timing gears & cam
Carb
Bits

J

 

[Anko]

Hi

Most of the people start with the engine block or the base/support (in case of a vertical steam engine type)

After that you make the inside pieces, but there is no order at all, start with the piece that you are more confident.

a tip: make first the cylinder bore, then a maching piston, because is more dificult to bore a precision hole than turn a outside diameter.

Saludos

 

[BronxFigs]

You guys are great. I knew if I asked you would help me think like a machinist. I am really psyched to start making chips, but I want to do the first build using some careful reflection about what needs to be done.

I will make mistakes. I don't care. I'll do it until it's right. If I get stuck, you guys will surely help.

I learned more in two months from you guys on the forum than all my years of reading. Reading = theory. Doing = reality with results.

Thanks for all the kind suggestions. ( I think either a V-2/V-4 Flamer will be the first build... no carbs. no fuel systems, wires, spark-plugs, etc....and, if machined correctly, the engine will turn. That's my goal. The engine should at least move. My standards are high). When I light the flames, and the engine actually runs....you'll hear the screaming and yelling. I can very easily revert to childhood in a split second.


Frank

 

[Tin Falcon]

Thanks for all the kind suggestions. ( I think either a V-2/V-4 Flamer will be the first build..

for a beginner the general consensus here is start with a simple single cylinder air/steam engine. then work from there. the LMS oscilator or the Mcabe runner are good starter engines. these engines are faily forgiving if the machining is not perfect. My second Mcabe runner runs on breath power.

There is a high level of interest in flame lickers and Stirling engines .
these engines produce little if any useable power and need to be leak free and virtual friction free in order to run. fit and finish of mating parts needs to be spot on.
So unless you are starting this hobby with years of machining experience to tight tolerance Keep it Simple to start.

As far as order of machining you can either start with the base and build part by part on top of it or start with the cylinder then build on that when all the mating parts are done mount it to the base. I am thinking a mill engine or flame licker here.
in a production shop or in an ideal situation you can just make all the parts to print then assemble. This is possible team build one parts all fit together. And the parts were made in 10 different shops.
But there is mothing wrong with making one part then making more and adding to it.


Tin

 

[Mosey]

A master said to me..."start with the scariest part first, then when you screw up, you can just redo it until it's right, and move on".
I find that the way to NOT screw up, is to make sketches of the part before starting machining. Too lazy? Yup, but it really works. It's really a shortcut.
Mosey

 

[Brian Rupnow]

Everybody approaches this from a different angle. I like to make the most difficult pieces first. That way, the job gets easier as you go along. There are a billion half finished models setting around the world, because people started with the easy parts, and when they got to the most difficult bits, they found that their skill level didn't extend to making such complex parts, the build stalled and got put up on a shelf or away in a box, never to be completed. Yes,--Do make the cylinder first. Its much easier to turn the piston to a diameter that matches the bore than the other way around. The most difficult part (for me anyways) is the crankshaft. The next most difficult part, if its an internal combustion engine, is getting the valves to seal.--Of course, you have to have 90% of the engine built before you can find out if your valves are going to seal properly or not. I don't recommend any stirling, flame licker, or other heat cycle engines for beginners in model engine building. As Tin pointed out, they develop such little power that they are extremely difficult to get running. internal combustion engines have their own set of difficulties. The easiest engines are the single cylinder engines which run on compressed air. They are very forgiving, their are a thousand free plans out there, and you don't need to buy any castings.----Brian

 

[Philjoe5]

I like to look at the drawings and decide which parts I'll have the most difficulty making. I make them first, then, feeling confident I start making the rest of the parts.

A few times though, some simple looking part gave me fits. But that's the beauty of a scratch built engine, go to the stock pile and start over....now wiser???

When I light the flames, and the engine actually runs....you'll hear the screaming and yelling. I can very easily revert to childhood in a split second.

Many of us have experienced this

Cheers,
Phil

 

[Septic]

My own preference for any build project is to choose parts according to the time available on the day, as I like to make sure that individual parts are finished in one go....

 

[BronxFigs]

Never considered the tight tolerances involved with the Stirlings and Flamers, nor the difficulty in getting them to run. Now, maybe a Compressed-Air single or V-Twin is probably a better choice.

I can see that there are many different ways to approach an engine-build. All have merit, and logic.

Thanks for the great advice.


Frank

 

[Tin Falcon]

Yep good advice . hardest scariest part first makes a lot of sense.
And i agree sketch each part on a 3x5 file card make notes hand or computer does not matter but sketching helps you machine it on paper.
It is the trained eye hand and mind that makes a craftsman. Drawing trains the eye hand and mind to work together.

tin

 

[gbritnell]

Personally I would start with the crankcase, or the head. My reasoning for this is that you make the holes first and then fit the shafts, bushings etc. to the existing holes. It's easier to turn up a part then to try and modify a hole that's already been bored or reamed.
The only exception to this would be the crank and connecting rods. You would want to make the crank first and then the rods as it's way easier to make a new rod if you mess up then having to redo the crankshaft.
Other than that just have fun.
gbritnell

 

[Briank]

Hi Frank,
With me, every engine is different, and sometimes complexity challenges me to take on the most difficult aspects first- seeking encouragement, I guess, for the other tasks! But in general, I like to begin with a buildable base so that I can see the engine develop as I add completed parts and assemblies. Once the base and standards and engine support are completed you usually can proceed in almost any direction, depending on your whim. I think you've arrived when you can survey a set of plans and say to yourself with some assurance, "I can build that!"

Have fun,
Brian

 

[cncjay]

whats your reccommendation for v twin, for beginners?

 

[Ed T]

A single cylinder one.

 

[BronxFigs]

All very interesting comments. I have been following the evolution of this thread, and I'm on the brink of finalizing negotiations that will allow me to 'rent' a shop and to use all the machinery in it. I will have a large lathe, milling machine, etc. plus a friend who has decades of experience building large-scale steam trains, engines, like the PEARL, and a triple expansion engine from Elliott Bay. Making some chips will be in my near future....I hope. I'm excited, just like a kid.

I probably will start with either a bar-stock, compressed-air engine, or, open column, steam-engine. I can run either engine off air, or, steam, if it's available. Engines will be made just for the sake of building something that will spin. I have plenty of bar-stock, plate, etc. that I have bought over the years, and finally, it will be good to turn this into something useful.

Thanks for all the suggestions and for the guidance that I had asked for.


Frank

 

[jwcnc1911]

Frank,

I'm excited for you too! After hearing what you're planning to build, I can't wait to see some progress pics!

Good luck, I hope everything works out!