Author Topic: My Ordinary Little Hit & Miss Engine  (Read 26738 times)

Offline rudydubya

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My Ordinary Little Hit & Miss Engine
« on: September 22, 2015, 07:28:25 PM »
This is a small, horizontal, air-cooled, four-stroke hit & miss model engine of my own design.  There's nothing unique about it, it's very ordinary, just a little smaller than most.  It has 3" flywheels, a 1/2" bore, 3/4" stroke, and was built from bar stock.  It has a solid-state ignition triggered by a Hall effect sensor and runs on Coleman camp fuel.

It's finished already, but I thought some of you might be interested in seeing my build pictures before I show you the finished engine.  It took me a couple of years to complete, but a lot of that time was spent adding things to my machines (cheap digital readouts, a home-made power feed, etc. for the mini-mill, readouts to my mini-lathe, etc.) and other distractions.

This is what the engine will look like.


I did the work on my mini-lathe and mini-mill.


I made the flywheels first, so I'll show them next.

Rudy
« Last Edit: July 09, 2017, 07:39:15 PM by rudydubya »

Offline gbritnell

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Re: My Ordinary Little Hit & Miss Engine
« Reply #1 on: September 22, 2015, 07:31:34 PM »
Nice looking engine Rudy. I have one a touch smaller and it runs well so should yours.
gbritnell
Talent unshared is talent wasted.

Online fumopuc

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Re: My Ordinary Little Hit & Miss Engine
« Reply #2 on: September 22, 2015, 07:38:31 PM »
Hi Rudy, I will following along. I like bar stock engines of that style.
Kind Regards
Achim

Offline tvoght

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Re: My Ordinary Little Hit & Miss Engine
« Reply #3 on: September 22, 2015, 08:42:38 PM »
Looking forward to seeing it, Rudy.

--Tim

Offline Perry

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Re: My Ordinary Little Hit & Miss Engine
« Reply #4 on: September 22, 2015, 09:26:23 PM »
Oh yes pictures please  :popcorn:

Offline b.lindsey

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Re: My Ordinary Little Hit & Miss Engine
« Reply #5 on: September 22, 2015, 11:56:33 PM »
Nice looking engine Rudy, and I like the smaller size too!!

Bill

Offline rudydubya

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Re: My Ordinary Little Hit & Miss Engine
« Reply #6 on: September 23, 2015, 06:05:14 AM »
Thanks everybody for the interest and encouragement.  Much appreciated.

The flywheels have 6 spokes, are 3 inches in diameter and 0.3 inches thick at the rims and hubs.  The spokes are straight, 3/16" wide and 0.1 inch thick.  I planned to use setscrews through the hubs to lock the flywheels to their axles like I did on the Upshur I built a few years ago, but as I explain below, I changed my mind...


I started with 3" square plates of 3/8" thick 1018 cold-rolled steel, center-drilled and sawed off at the corners.


The pieces were too big to fit in my lathe chuck, so with the aid of some emery paper on the backs to improve friction, I used a live center to hold the plates against it (See John's tutorial here for more info). I took light cuts until the rims were rounded to size.  They now fit in my 4-jaw chuck.


I turned the flywheels down on both sides and recessed the centers.  I also drilled and reamed the holes for the axles.


I used my CAD program to get X-Y coordinates and angles for milling the spokes on my rotary table (symmetry is your friend).  Things went well, I only screwed up one flywheel that had to be re-made (an unfortunate loose clamp).


Here's what I ended up with.  I'll clean up some of the remaining machining marks later.


Some of you may have noticed that the plain hubs on these flywheels are not the tapered split hubs shown on the assembly drawing in my first post.  I changed the flywheels to tapered hubs after I had finished these.  There was considerable interest in tapered hubs on some of the forum builds while I was making these flywheels, so I decided to try my hand at making some.  I'll show those next.

Rudy
« Last Edit: July 11, 2017, 08:19:22 AM by rudydubya »

Offline Roger B

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Re: My Ordinary Little Hit & Miss Engine
« Reply #7 on: September 23, 2015, 10:17:38 AM »
Looks to be a nice little engine  :praise2: I will be following along  :wine1:

You've a nicely laid out workshop as well  :ThumbsUp: Was the picture before or after you made the engine  ;)
Best regards

Roger

Offline Dave Otto

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Re: My Ordinary Little Hit & Miss Engine
« Reply #8 on: September 23, 2015, 01:27:34 PM »
Nice work and design; I will be following along.

Dave

Offline NickG

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Re: My Ordinary Little Hit & Miss Engine
« Reply #9 on: September 23, 2015, 06:58:47 PM »
Hi Rudy,

I am in the process of designing an engine like this myself. It looks quite similar though as you say, there are that many variations on a theme it's difficult for them to be unique. I have tried to design mine as simple as I can to make to give me the best chance of getting a running engine!

This will be great for me to follow and I might learn a few things before I cut metal! Nice work.

Thanks,

Nick

Offline rudydubya

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Re: My Ordinary Little Hit & Miss Engine
« Reply #10 on: September 23, 2015, 07:47:33 PM »
Thanks again to everybody for following along and keeping me company.

Roger, if you're referring to the picture of the machines, I took that after the build was finished when I realized that someone might be interested in what I built the engine with.  Sadly, I have cleanup issues, and the area was never that neat and clean while the build was going on.

Nick, good luck on your project, I'll look forward to seeing it.  I made up a lot of things as I went along, and changed my plans several times.  The hubs were just the first of several changes and do-overs.  As for learning from my build, I hope I can contribute, but be forewarned that I'm still a novice machinist and what you see in the pictures might be only a bad example...

Regards,
Rudy

Offline rudydubya

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Re: My Ordinary Little Hit & Miss Engine
« Reply #11 on: September 23, 2015, 08:29:22 PM »
Now, as for the new hubs, they're like those Chuck is making for his 2-cylinder horizontal build.  Mine will be attached to the flywheels with three 0-80 screws, and I'll also drill and tap for three jackscrews.  I'll just put my existing flywheels back in the lathe and re-bore them at an angle, and then make the hubs at the same angle.
 
My design had the crank axles 1/4" diameter, and I didn't have a boring bar small enough to do a taper that small in the flywheels.  I ground a small cutter from some round HSS, but it didn't turn out very good, too much flex, maybe not sharp enough either, so I abandoned it.  I may never be very good at making or grinding lathe tools.  Anyway, I finally used a small end mill in a boring bar holder.  Here you see the setup.  The compound rest is set over (about) five degrees for the 10-degree included angle I wanted.  I tried it out first on the flywheel I had screwed up earlier to make sure everything was correct and it would work OK.  It worked OK.


I made matching hubs by running the lathe backwards and cutting on the back side, then drilled and reamed for the axles.  After I parted them off I put them on a piece of 1/4" drill rod and cut the slots with a hacksaw.  I used the ends of the clamps to guide my cuts.


I used some Loctite to help secure the hubs to the flywheels while I drilled and tapped them for their lug screws and jack screws.


Did I mention that I made things up as I went along?  The tapered hubs turned out OK, and they were a good learning experience, but I decided 1/4" axles were going to look too big for my model and changed to 3/16" instead.  I also decided to go with aluminum hubs instead of steel.  I didn't have to change the flywheels any, I just re-made the hubs out of aluminum with the smaller bore.  I don't have any pictures of doing that, but it was just a repeat of what I had already done.

Next time we'll get started on the upper half of the frame.

Rudy
« Last Edit: July 12, 2017, 07:39:43 AM by rudydubya »

Offline Don1966

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Re: My Ordinary Little Hit & Miss Engine
« Reply #12 on: September 23, 2015, 11:35:06 PM »
Outstanding work Rudy, I will be tagging along. I do like the design its very interesting. By the way I made this flywheel spreadsheet some time back and it calculates straight spoke flywheels for you.  http://www.modelenginemaker.com/index.php/topic,1271.0.html

Don

Offline rudydubya

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Re: My Ordinary Little Hit & Miss Engine
« Reply #13 on: September 24, 2015, 04:28:19 PM »
Don, thank you.  I remember your flywheel spreadsheet, looked like a nice tool for flywheel layout, I filed it with my other layout tools.  I didn't need one this time, the milling coordinates were a by-product of my CAD drawing.

The frame is in two sections, an upper part and a base, with bearing blocks for the main bearings.  I did the upper part and the bearing blocks first.  The recess at the front is for the rear end of the cylinder, and the stepped cutouts at the rear are seats for the bearing blocks.  I'll attach the bearing blocks to the frame with some 2-56 screws, and ream them out for some 3/16" ID bronze axle bearings.  The holes you see on the near side of the frame are for a pushrod guide and the cam-gear shaft (I made my gears a few years ago, so I knew where to locate the shaft).


I made the upper part of the frame from a solid block of 6061 aluminum, milled it to size, and drilled and tapped the side holes.  I also center-drilled at the center of the side curve.


The block was then turned on its end and center-drilled deep at the cylinder axis, along with the four clearance holes for the cylinder mounting screws.  The clearance holes were then drilled deeper than the recess depth plus the design thickness of the frame front.


I then moved the block to my 4-jaw chuck on the lathe, and centered it on the cylinder axis.


The chuck and block were then moved to my rotary table, already centered on the mill.  I used the rotary table to mill the cylinder recess and the top curve of the frame.


After I finished at the mill, I moved the chuck and block back to the lathe and drilled and bored out the clearance hole for the cylinder.  I bored it deep enough to clear what would be the back of the frame front plus some extra.


Next post we'll make the bearing blocks and shape the frame.

Rudy
« Last Edit: July 13, 2017, 07:16:42 AM by rudydubya »

Offline rudydubya

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Re: My Ordinary Little Hit & Miss Engine
« Reply #14 on: September 24, 2015, 05:04:11 PM »
After I had bored out for the cylinder, I removed the block from the lathe chuck and moved it to the mill vise.  I put some sacrificial aluminum spacers at its top and side so the cutters would clear the vise, and progressively drilled out and milled out material to rough out the top profile of the frame.


I set the frame on its bottom and finished milling the top flat, then milled the bearing block seats across the rear.
 

The bearing blocks were milled together as a single, long block and checked for fit with the frame.


I then clamped the block to the frame for drilling.  The block and frame were drilled, and the frame was tapped for 2-56 screws.


Continued...

Rudy
« Last Edit: July 13, 2017, 07:22:56 AM by rudydubya »

 

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