Author Topic: Four cylinder scale engine  (Read 22195 times)

Offline ThomasM

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Re: Four cylinder scale engine
« Reply #15 on: January 29, 2017, 09:07:16 PM »
Actually i wanted to work on the bottom end of the crankcase but i had to resist the wish to clamp it down on the front and the end. There would be two disadvantages when i would have done that.

First there would be much stress on the thin side walls of the part because the clamps would actually try to bend it. The risk of cracking it is to high. Bolting it down trough the cylinder holes would be possible but i have to machine the inner top surface to accept the middle camshaft bearing ( a split one) and every relocation of the clamps would make it necessary to re align the part and find x/y - zero. 

So i used my little time i had today to make a fixture that allows me to find the parts x-y zero repeatable and hold it in any position i need to reach all the surfaces not machined yet.

 First Picture shows the jig pushed against some stops on the milling table and the spindle is located on the marked x/y zero.
 X/y zero is between the cylinder bores 2 and 3. The red corners are the two i machined to an exact 90 degree angle. I will prefer this corners later for indicating.

 Picture two : After removing the jig from the table it is bolted to the crankcase through some of the head bolt threads . I use not all of them.

 Picture three shows the whole thing clamped down on the milling table ( again pushed against the stops ) .

 Now i have access tho all surfaces without relocating clamps or damage the casting.
 
 

Offline zeeprogrammer

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Re: Four cylinder scale engine
« Reply #16 on: January 29, 2017, 10:14:33 PM »
Looks very interesting.

You might have mentioned it, but I can't find it...what's the size?
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
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Offline Zephyrin

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Re: Four cylinder scale engine
« Reply #17 on: January 30, 2017, 08:50:25 AM »
This will be a interesting thread to follow, starting from home shop castings, nice.

Offline Chipswitheverything

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Re: Four cylinder scale engine
« Reply #18 on: January 30, 2017, 01:06:04 PM »
Thanks for a great build log and photo gallery on your interesting engine project , Thomas.  Huge admiration for your ability to make the complex patterns and do your own casting.   Dave

Offline tvoght

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Re: Four cylinder scale engine
« Reply #19 on: January 30, 2017, 04:06:44 PM »
I will enjoy this build, Thomas. You don't have to be a "Ford man" to appreciate the Model A engine.

--Tim

Offline ThomasM

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Re: Four cylinder scale engine
« Reply #20 on: January 31, 2017, 08:17:40 PM »
Thank you for all the comments.
I am on work and will not be at home until Friday. Normally i am at home every late evening so this is an exception.
I will progress on this Saturday.

@ zeeprogrammer : I have the drawing not with me so i have to wait to post detailed numbers on the engine. As an indication : The crankcase is 175 mm long and the engine will have 24 mm bore and 28 mm stroke. The displacement will be about 50 ccm.


Offline metalmad

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Re: Four cylinder scale engine
« Reply #21 on: January 31, 2017, 09:46:37 PM »
Hi Thomas
I currently don't get a lot of time but will be following along as I can.
Love The thin Wall casting!
Pete
A little bit every day, sometimes the same little bit

Offline ThomasM

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Re: Four cylinder scale engine
« Reply #22 on: February 05, 2017, 01:26:29 PM »
Hello,

I just want to keep you updated what i did yesterday.

The machining of the lower side of the crankcase is finished. I also machined the front and end of the case to the right angle to be able to use this surfaces as a reference when clamping to do the camshaft boring. The front and end is not machined to size because this surfaces had to be machined together with the oil pan to give a suitable sealing surface.

Also the crankshaft main journals are finished. The crankshaft will run at roller bearings at the front and end and a split bronze bearing in the middle.

The next thing i will do is the crankshaft. I need it to locate the exactly position where the crankshaft leaves the crankcase to bore the the journals for the camshaft. The camshaft will be driven by gears so the distance between them has to be precise.

 @ zeeprogrammer : The stroke of the engine will be 30 mm not 28 mm as i have posted a few days ago.
                                 I also posted a picture of the basic outer measurements of the engine without the gearbox.

I will keep you informed about the progress. Actually i see a few other topics in this forum with absolutely unbelievable engine projects. The V10 engine is in fact the best i have ever seen in model engine building and the 8 cylinder inline engine in the other just started topic will also become a masterpiece when finished.

Best regards,
Thomas

Offline ThomasM

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Crankshaft finished
« Reply #23 on: February 12, 2017, 04:14:59 PM »
Hello,

As i already told the next thing to do is the crankshaft and here it is.

On this crankshaft i had to use normal steel. I Europe this material is called St-37 ( S235 ) and it it is good for welding and general purpose.

Unfortunately it is not very good for turning. On my previous four cylinder engine i used leaded steel 9SMn28 ( SAE 1213 ? ) and this was a pleasure to machine but the crankshaft was based on a rod material not a flat material like this crankshaft.

Unfortunately i was not able to buy flat material optimized for turning or milling like 9SMn28 ( 1213 ) so i had to use what was available.

- Picture one shows the material cut to size and clamped to the tool support ( ? ) of my lathe. I had to use the lathe to machine the index bores
   because the z - axis of my mill is not high enough to do this on the mill.

 - Picture 2 : After that i machined the holes for fixing the material to the milling table to mill the shape of the crankshaft as best as possible. My
   plan is always do do as much work as possible on the mill and use the lathe only for turning ( or grinding ) the bearing pins.

 - Picture 3 and 4  show the crankshaft after the finishing pass and after i sandblasted it.

 - Picture 5 : I used my support grinder for machining all the bearings and crank pins while holding the crankshaft between centers whit the index
    holes. With this material the tool pressure while turning it would be to high and the surface finish would also not be usable.

 - Picture 6 : Finished crank pin.

 - Picture 7 : After rouging out the ends i also grind these.

 - Picture 8 : After i parted of the ends with the index holes on my band saw i had to use my steady support to face and chamfer the ends of the
   crankshaft.

 - Picture 8 : Finished crankshaft. I love it.

Now i am looking forward to do a bit of foundry work and pattern making . I need connecting rods and want to cast them because cnc machined rods would not look good in this engine.

Best regards,
Thomas

Offline ThomasM

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Crankshaft finished
« Reply #24 on: February 12, 2017, 04:18:11 PM »
Only 8 pictures where possible i one post. So here is the last picture...

Offline fumopuc

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Re: Four cylinder scale engine
« Reply #25 on: February 12, 2017, 05:26:59 PM »
Hi Thomas, thanks for showing your way to make the crank shaft.
Kind Regards
Achim

Offline gerritv

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Re: Four cylinder scale engine
« Reply #26 on: February 12, 2017, 06:24:36 PM »
The end result looks like it was drop forged.

Gerrit
Don't confuse activity with progress

Offline Roger B

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Re: Four cylinder scale engine
« Reply #27 on: February 14, 2017, 11:39:44 AM »
Excellent work on the crankshaft  :praise2:  :praise2:

I used C45k for the last two crankshafts I have made. What grinding wheel are you using and at what speed?
Best regards

Roger

Offline Art K

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Re: Four cylinder scale engine
« Reply #28 on: February 16, 2017, 03:51:00 AM »
Thomas,
I wanted to let you know that I'm following along. I have to make an effort in the evening after I get home from work to reply. When I start work at 6:00 am your build is still active on the side but not when I leave. Are you going to use a water pump? or thermo siphon? Great work on the castings by the way.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline ThomasM

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Re: Four cylinder scale engine
« Reply #29 on: February 18, 2017, 01:17:45 PM »
Hello,

Sorry for being a little late to answer but actually i am very busy from Monday to Friday on my job. Luckily this is only a temporary situation and will only last for the next about twenty to  years when i hopefully retire.....

@ Gerrit : Sandblasting was the easiest way to get rid of the different surface looks at the machined and unmachined surfaces of the part.

@ Roger : Now when you have told me i remember that i have used C45 steel in the past for a part i cant remember. I remember also that this
    was relatively easy to machine. For my next crankshaft i will look for this material because it should be available as flat material everywhere.
 
    The question about the grinding wheel is something i was a little afraid of ....
    Please dont laugh but i used a 1,5 mm parting disc ( diameter 125 mm ) for a hand grinder. The  rpm setting on the support grinder is about
    8.000 rpm which is the limit for this disc. The disc is specified for use on stainless steel, i think this type is a little finer.
    The rpm setting on the lathe was about 50 rpm the lowest i can reach with my  retro fitted frequency converter .
    I dont tell this is the way to go but for me there are a few advantages to use this disc in the support grinder. At first i dont have to mess with
    the condition of the grinding surface like flatness and the exact angle in relation to the part. The second point is that  i was able to remove
    much metal from the milled crankpins without the necessary to use a turning tool without the risk of ruin the part because of the heavy tool
    loads. I had to avoid side loads on the parting disc when i was removing the excess material by cutting into the steel the same way you do
    when using a hand grinder. Only the last ginding passes to the finished size where done by traveling in  the x axis direction whith only little
    removement of material. The surface i got after i was on finished size ( 12.00 mm on all bearings ) was nearly perfect and i only had to use
    a stripe of sanding paper for a few seconds to bring it to visually perfect condition.

    Again, i dont say this is the way to go but i was able to make the crankshaft by doing so and it gives me a very good result.
    Of course you have to make sure to protect your late from the grinding dust and clean it after the procedure.

@ Art : I will try it without a water pump like ford did on the original engine. I hope for stationary running without or with little loads it should be
             ok. Whe the engine will run at idle for a unlimited time without overheating i am happy. If not i will ad a water pump like many Model A
             owners also did.

Now i proceed with making the connecting rods.I decided not to cast them like i told because milling them with the cnc would take less time.
I hope i can finish them today and make another post.

Thomas
   
« Last Edit: February 18, 2017, 01:23:45 PM by ThomasM »