Building an Oscillating Engine for my first engine

[malofix]

@methuselah1 I'm reluctant to try out the first option. For the second option i didn't quite understand it can you elaborate more?

@ShopShoe i can change the spindle speed(at the same time the feed) with a potentiometer. For the grinder i'm thinking buying a cheap one, see the attachment for the model i'm thinking. I hope it is suitable for grinding tool bits. It is 150watt, has 150mm diameter grinder and 2950rpm.

 

[ShopShoe]

malofix,

What I think methuselah1 is saying in option 2 is that you make the flywheel from more than one part and then put them together. You would use brass as it can be soldered together. For aluminum, you would secure the parts together in an assembly with loctite.

In my opinion, brass would provide more mass and better "act like a flywheel" than aluminum, which is too light. With the loctite option, you could also make the hub and inside part of the flywheel of aluminum, and make the outer rim out of brass. Many makers have done this as brass is more expensive than aluminum.

--

I might suggest that you could make a temporary flywheel with fewer features (just a "disk" with a hub, out of brass or steel) in order to move on with the project and not get stuck at this stage of the build. You could make the "real" flywheel later. You could also purchase a flywheel from various suppliers to the hobby, although that may be hard to do from your location.

--

That grinder may work for you. The main things to consider are whether the tool rests are sturdy enough and whether the wheels are perfectly round and run without vibration. You should get a wheel dressing tool to make sure the wheels are round and are also clean and dressed to grind a flat face into whatever you are grinding. You should be able to find many tutorials for toolbit grinding online. It takes practice to grind cutters, but once you learn it, you will probably enjoy being able to sharpen all kinds of things.

You should also have safety glasses or a face shield, which you should also use when using the lathe. I also recommend a bench stone for touching up your ground cutters after using the grinder: That can also be used to sharpen your knives and scissors.

--ShopShoe

 

[methuselah1]

Fot surface speeds, aluminium and brass (especially) are very forgiving. You can do it on those diameters without adjusting spindle speed.

 

[methuselah1]

Fot surface speeds, aluminium and brass (especially) are very forgiving. You can do it on those diameters without adjusting spindle speed.

 

[malofix]

I might suggest that you could make a temporary flywheel with fewer features (just a "disk" with a hub, out of brass or steel) in order to move on with the project and not get stuck at this stage of the build. You could make the "real" flywheel later. You could also purchase a flywheel from various suppliers to the hobby, although that may be hard to do from your location.

That is ideal, i dont really wanna stuck at a part since i've already made many mistakes that put me behind, my indicators on lathe arent the "real"ones, so if i take a cut that is 1mm it actually takes 2mm. It shows me the diameter that is to be cut and this led me to over cutting, i forget this all the time somehow.

I already started piling scraps

 

[Sprocket]

I have done that kind of section on a flywheel using regular turning cutters, one to cut left, the other to cut right. You work from near one side (center or rim)
and make facing cuts until you need to change cutters and go the other way. It's a little time consuming, but easy on the machine. Set the tool so the point is a little ahead of the shaft so it clears at the edges.
Hope that makes sense. I'll try to find a picture.
Doug

 

[malofix]

I have done that kind of section on a flywheel using regular turning cutters, one to cut left, the other to cut right. You work from near one side (center or rim)
and make facing cuts until you need to change cutters and go the other way. It's a little time consuming, but easy on the machine. Set the tool so the point is a little ahead of the shaft so it clears at the edges.
Hope that makes sense. I'll try to find a picture.
Doug

Yes that makes sense to me. I'll try it out.

 

[malofix]

Where would you start using a dead or live center? What is the minimum piece lenght and thickness i should start using one? Scrapped a thin piece while trying to cut it thinner, it bended like crazy. I think this might be the cause behind different measurements on my previous pieces.

 

[Sprocket]

Try cutting only short areas at a time on your thin shaft. There is a good picture of this in Terry Mayhugh's thread on the Ford 300 Inline Six, Page 7. I can't figure out how to link it here. He is cutting valves from 3/8" stock to 1/8" stems. He cuts it in short segments to minimize deflection. If you are using a three jaw chuck, maybe try to avoid turning it in the chuck as you move it out to keep it concentric. It may not matter, but three jaw chucks aren't always accurate.
If the part isn't too long, you won't have too move it.
Hope that helps,
Doug

 

[Steamchick]

Mal O'fix: I try to keep no more than "3 diameters" projecting from the chuck or a larger diameter. >4 diameters means deflection is too great. - tapers form.
- But it does depend on material, speeds and feeds and size of cut. to come down to size on a bit of brass, I may be removing metal at 0.02" cuts, then for the last 0.02" to size, a single cut at 0.01", 0.005",0.002" and finally a couple of cuts at 0.001". And I am in "no hurry to get it wrong and waste time re-making it". These last cuts are: "measure", cut 10%, check measure, finish cut: - Repeat.
You'll get the hang of it after ruining something that took a bit if time and effort.... - Learn once, improve if wrong, then don't make the mistake again! - We've all been there and done that!
Irish Quality assurance is the best, the way they measure twice: "to be sure to be sure!"
Enjoy!
K2

 

[malofix]

There are numbers in the plan like 6-32, 10-32, 1/4-28 threads. What does that mean? What metric size should i use instead?

And what does that mean(below picture)

 

[coulsea]

there is a thread chart in the downloads section of this forum
https://www.homemodelenginemachinist.com/attachments/thread-chart-doc.109767/if you look up 10-32 it is 4.8 mm so you could use 5mm or 4mm depending on clearance around it so it does not interfere with another part.
The R0.03 max is the radius of the corner, so how much of a curve it has. I think that the part is the flywheel and that corner does not interact with any other part so it doesn't really matter what shape it is.
when converting plans to metric try not to worry about things that don't matter, for example the flywheel is 63.5mm but anywhere from 60mm to 65mm will do, but things like cylinder pivot to port distance will affect at least two other measurements on other parts.

 

[Steamchick]

The radius in the corner is the minimum radius that you should have on the lathe tool that cuts into that corner. A bigger radius is MUCH stronger (stress concentration factor), so if you use a "sharp" pointed tool, the part of the flywheel can crack and break, but if you use something larger than specified, you never will have a breakage.
Without all the dimensions, I cannot deduce the stress concentration factor, but a "pointed" tool (the convergence of 2 ground flats) will have an SCF of maybe 10 to 100, but at 0.030" this is SCF reduced to 5.... at 0.060" this reduces further to 2.5 (Twice as strong). It is an Hyperbolic function - not linear - so don't try and "simply" extrapolate these things. Refer to a proper text book of stress concentration for a proper answer. Fatigue strength is also a non-linear function but someone may have defined such a min radius to increase the fatigue life by a factor of 2, or 5, or 10, or more?....?
Usually, these dimensions are specified only where someone has experienced real cracks and breakage! (The highest stressed zone always fails first).
Personally, I have always used larger radius tools (1mm or more) wherever possible, as I was taught as a lad, and having tuned various things to breakage (and failure is always at the highest stressed point), often at a machined "sharp" corner.
One example, when (professionally) designing components that were stressed "close to the limit" I experienced a part that had a radiius of 1mm (0.040") in the corner, but failed on durability test at only a couple of thousand operations (not good enough) and the solution was a min 3mm radius - when it never failed. (Stress concentration is THAT important, e.g. on stub axles of car front wheels, where on "correct" parts you'll find large radii used where needed, but can get "aftemarket parts" with sharp corners (!!!) that will fail prematurely.... - and while the material choice and control, and control of heat-treatment, are also critical, the stress raiser will still "break the best and all the rest"!
EVERY feature put on the drawing by the designer is there for a reason, so please keep asking and learning what they all do. Knowledge is a "gift of humanity" to be shared, not ignored, or denigrated (as seems to be the fashion amongst modern youth!). (There I go again, using words I can't spell, and as the spell checker didn't correct it I had to check my 1950s dictionary! Written by scholars, for all who can read to use..., and "the batteries have not run flat" on that paper book!).
Those that don't know/don't care will ignore stress concentration features at their peril, (Or someone else's peril? - !!!).
Enjoy modelling, it is usually safer in the workshop than "out there in the great wide world"!
K2

 

[malofix]

The radius in the corner is the minimum radius that you should have on the lathe tool that cuts into that corner. A bigger radius is MUCH stronger (stress concentration factor), so if you use a "sharp" pointed tool, the part of the flywheel can crack and break, but if you use something larger than specified, you never will have a breakage.
Without all the dimensions, I cannot deduce the stress concentration factor, but a "pointed" tool (the convergence of 2 ground flats) will have an SCF of maybe 10 to 100, but at 0.030" this is SCF reduced to 5.... at 0.060" this reduces further to 2.5 (Twice as strong). It is an Hyperbolic function - not linear - so don't try and "simply" extrapolate these things. Refer to a proper text book of stress concentration for a proper answer. Fatigue strength is also a non-linear function but someone may have defined such a min radius to increase the fatigue life by a factor of 2, or 5, or 10, or more?....?
Usually, these dimensions are specified only where someone has experienced real cracks and breakage! (The highest stressed zone always fails first).
Personally, I have always used larger radius tools (1mm or more) wherever possible, as I was taught as a lad, and having tuned various things to breakage (and failure is always at the highest stressed point), often at a machined "sharp" corner.
One example, when (professionally) designing components that were stressed "close to the limit" I experienced a part that had a radiius of 1mm (0.040") in the corner, but failed on durability test at only a couple of thousand operations (not good enough) and the solution was a min 3mm radius - when it never failed. (Stress concentration is THAT important, e.g. on stub axles of car front wheels, where on "correct" parts you'll find large radii used where needed, but can get "aftemarket parts" with sharp corners (!!!) that will fail prematurely.... - and while the material choice and control, and control of heat-treatment, are also critical, the stress raiser will still "break the best and all the rest"!
EVERY feature put on the drawing by the designer is there for a reason, so please keep asking and learning what they all do. Knowledge is a "gift of humanity" to be shared, not ignored, or denigrated (as seems to be the fashion amongst modern youth!). (There I go again, using words I can't spell, and as the spell checker didn't correct it I had to check my 1950s dictionary! Written by scholars, for all who can read to use..., and "the batteries have not run flat" on that paper book!).
Those that don't know/don't care will ignore stress concentration features at their peril, (Or someone else's peril? - !!!).
Enjoy modelling, it is usually safer in the workshop than "out there in the great wide world"!
K2

Then radius on that corner will be formed by the cutting tool naturally i suppose. It's good to learn such design features.
I hope i'll keep asking as long as someone answers.

Thanks.

 

[Steamchick]

Correct: Are you using a commercial tool, or home ground? Many carbide inserts (that I use) have calibrated radii for the cutting edge, but most "simple tools" are sharp cornered and you need to re-grind to the radius required (that I have done many times!).
K2

 

[Mike Ginn]

there is a thread chart in the downloads section of this forum
https://www.homemodelenginemachinist.com/attachments/thread-chart-doc.109767/if you look up 10-32 it is 4.8 mm so you could use 5mm or 4mm depending on clearance around it so it does not interfere with another part.
The R0.03 max is the radius of the corner, so how much of a curve it has. I think that the part is the flywheel and that corner does not interact with any other part so it doesn't really matter what shape it is.
when converting plans to metric try not to worry about things that don't matter, for example the flywheel is 63.5mm but anywhere from 60mm to 65mm will do, but things like cylinder pivot to port distance will affect at least two other measurements on other parts.

Thats a really useful chart. In the UK we also have what is known as ME threads which have 60, 40 and 32 TPI in sizes up to 1/2 inch in Whit form. Very useful for small models but missing from the chart. I don't know if these are available in the US.
Mike

 

[malofix]

Correct: Are you using a commercial tool, or home ground? Many carbide inserts (that I use) have calibrated radii for the cutting edge, but most "simple tools" are sharp cornered and you need to re-grind to the radius required (that I have done many times!).
K2

I'm using carbide insert tools. Carbide inserts don't seem to be too expensive for the sizes i'll be using. But i think i'll also use home ground tools since appearently they offer more customization. This will wait for the time being however.

 

[packrat]

Quote "There are numbers in the plan like 6-32, 10-32, 1/4-28 threads. What does that mean? What metric size should i use instead? "
You could change to BA threads and bolts and nuts, BA size chart

 

[Richard Hed]

Quote "There are numbers in the plan like 6-32, 10-32, 1/4-28 threads. What does that mean? What metric size should i use instead? "
You could change to BA threads and bolts and nuts, BA size chart

If you are from the US, I would not do that, that is, I would not use BA. I bought castings from UK but short of buying all the BA threading tools from Britain, I could not use the threaded bolts and studs that came with the kit. I switched to comparable sized nuts, bolts and studs from US.

 

[malofix]

But things like cylinder pivot to port distance will affect at least two other measurements on other parts.

Is there a precise way to locate and mark locations to be drilled? I'm using my digital caliper to make markings on the paper firts then mark the metal using paper. Or use a metal ruler by the way of approximation.