Little Demon V8 - helpful hints (hopefully)

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Carbuilder

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This will be sort of a build log, but hopefully with a difference.

Here is what I am hoping this thread will provide. This will not be a normal build thread with many pictures of my finished parts. This will be more of a show and tell as to how I made the parts; how they were set up in the machine and how I made them that may be different from how others did it. And most important, I’ll show the mistakes I made on some of the parts and how I repaired them without having to machine a new part.

I’ll put an introduction to myself and my shop here, so you can skip this part and get to the meat if you like.

I bought my first semi-serious piece of machine shop hardware many years ago. It is a 3-in-1. Yes, one of those machines that everyone hates, recommends you never buy, never use, and really should be replaced with a full-size mill, lathe, and drill press. This is a Busy Bee unit (me being in Canada); same thing as the Grizzly G9729. Over the years I added a DRO and recently replaced the lathe motor with one from a treadmill to give me variable speed on the fly. It was a pretty good unit before these mods and is a very good one now. I also added a windshield wiper motor with a variable speed control to the right end of the leadscrew. This way I can control the speed of the cutter independent to the speed of the spindle, and dial the speed up or down on the fly.

I bought a small CNC mill a few years ago. I think this was literally the last one Little Machine Shop sold of this type; a Sieg KX1. Great little machine.

The last addition was very recent when I decided the lathe part of the 3-in-1 was pretty nice, but swapping between the mill and lathe functions requires a bit of set up time, so a new mill it was. I bought a PM-728VT. Now that is a nice mill!

The first thing I made on the 3-in-1 years ago was a small pin ball valve engine. Looked pretty nice but of course didn’t work. I made a lot of parts for car projects and other things, and then tackled a low temperature stirling engine (the Miser). This was made almost exclusively on the 3-in-1 so it is capable of good precision. And the most surprizing thing was, the engine actually worked the first time I set it up on a cup of hot water! So with that mastered, time to move on to something more challenging….the Little Demon. This has been going on now for a few years but I’ve recently gotten more serious about working on it.

I try and do as much on the CNC as I can, and here is my reason for this. First, I don’t always feel like being in the shop, so working on the computer doing the modelling and programming is still working on the engine without being in the shop. Second, when machining something there is a decent chance of doing something wrong; at least with me there is. By modelling and programming first, I can see what is going to happen before doing the machining. This is important for parts with many holes. A bit more on this later. Also, I still get a kick out of watching the machine do the work.

Please feel free to contribute to this thread if you are making a Little Demon, or any engine with similar parts. Particularly if you have hints and tips that could be useful to others.

I’ll start it off now and give you an idea of what this will be about. Oh, first of all here are the parts I’ve made or partially made so far. Block, carb, air cleaner, distributor, bell housing and adapter, crankshaft, connecting rods, water pump, oil pan, flywheel, rocker covers. Heads are in-work.

Well, this has been a longer intro than I expected, so the more interesting stuff will start with the next posting.

Rick
 

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Carbuilder

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Now that the wordy introduction is done, on to the crankshaft.

I’ve never made a crankshaft like this before and from everything I’ve read, it was going to be a challenge. The issue, as far as I could see, was that the drag of a lathe tool against a fairly flimsy crank can easily lead to it bending, jamming, and being ruined. So how to minimise this?

Here is how I did it. I do have a rotary table for my CNC mill; the 4th axis. But the mill is not huge and there is not room for the 4th axis and a 6” length of material sticking out of it. Here is where things get weird.

My new mill, the PM728 is beside the CNC mill. So I bolted the 4th axis onto the table of the PM mill, but left it plugged into the CNC mill. So I wasn’t using the 4th axis under CNC control, but just using the software to rotate it as needed manually. Here is the setup:

setup.jpg

The idea was that I could use the mill to machine away most of the material. I figured a rotating cutter would put a lot less stress on the part compared with cutting it in the lathe. I roughed out the main journals first, as those didn’t require any offset of the crank. So far, so good.

crank1.jpg

A test cut at the right and then on to the main journals.

crank2.jpg

I’ve bought a number of kits from Hemingway Kits over the years and highly recommend them. Oh, if you do any threading on the lathe, their retracting tool holder is fantastic! But I digress. I had their Keats Angle Plate kit for a while but never got around to making it. So a time out while I made it. OK, now I’m back. This holder allows for a fairly easy setup for offset turning.

crank4.jpg

Hemingway .jpg

So what I did was to slowly lower the cutter in the mill spindle, while using the 4th axis control to very slowly rotate the crankshaft. I would allow it one complete rotation and then lower it another .010 or so. Of course the surface finish was not good enough for a finished journal, so I left them all oversize to finish on the lathe. This way I only had a few thou to clean up and with slow and careful work didn’t bother with putting any filler pieces between the journals to stiffen it up.

Did it come out perfect? No, but hopefully close enough. Once back on the lathe I cleaned up the main journals to get the runout near zero. I was a bit surprized how flexible it is.

on lathe.jpg

I decided not to push my luck and machine the crank offsets to look more like a real crankshaft. I considered myself a bit lucky to get this far with my first crankshaft.

So that is my multiple mill, semi CNC, rotary table, crankshaft production. Of course a normal rotary table would allow you to do the same thing, just with a lot of cranking. But if machining the crankshaft right from the start on the lathe frightens you, maybe consider this method.

Rick
 

Carbuilder

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Thank you Steve. And thank you very much for designing this amazing little engine and providing support when we need it.

While I'm here, how about a small repair I made. Those with good eyes no doubt noticed the picture of all the engine parts that shows the timing cover with a strange piece sticking out of it.

Screen Shot 2022-01-02 at 7.23.35 PM.png

I machined this part on the CNC. With parts like this I leave small tabs (to keep the part from coming loose) and cut about .020" below the material thickness between the tabs. So I started this one going and then remembered I forgot to put a scrap piece under it; the cutter is going to go right through and into the table otherwise. So I stopped it, added 1/16" aluminum scrap under it and started it again. But I forgot to re-zero the upper surface of the material, so the cutter went .062" too deep. I stopped it when I realized, but the one hole that wasn't supposed to go right through, did.

I took a small piece of scrap I had, turned it to fit about .040" into the part, and pressed it in with some locktite.

Screen Shot 2022-01-02 at 7.28.12 PM.jpg

Cut it off, machined it almost flush, and another part saved. I also put an extra hole in it for some reason; I blame the CNC for that one. I plugged that with a small countersunk screw (not shown here).

Screen Shot 2022-01-02 at 7.30.25 PM.jpg

So don't think you have scrapped a part without giving some thought as to possibly fixing it.

Rick
 

rrocky

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This will be sort of a build log, but hopefully with a difference.

Here is what I am hoping this thread will provide. This will not be a normal build thread with many pictures of my finished parts. This will be more of a show and tell as to how I made the parts; how they were set up in the machine and how I made them that may be different from how others did it. And most important, I’ll show the mistakes I made on some of the parts and how I repaired them without having to machine a new part.

I’ll put an introduction to myself and my shop here, so you can skip this part and get to the meat if you like.

I bought my first semi-serious piece of machine shop hardware many years ago. It is a 3-in-1. Yes, one of those machines that everyone hates, recommends you never buy, never use, and really should be replaced with a full-size mill, lathe, and drill press. This is a Busy Bee unit (me being in Canada); same thing as the Grizzly G9729. Over the years I added a DRO and recently replaced the lathe motor with one from a treadmill to give me variable speed on the fly. It was a pretty good unit before these mods and is a very good one now. I also added a windshield wiper motor with a variable speed control to the right end of the leadscrew. This way I can control the speed of the cutter independent to the speed of the spindle, and dial the speed up or down on the fly.

I bought a small CNC mill a few years ago. I think this was literally the last one Little Machine Shop sold of this type; a Sieg KX1. Great little machine.

The last addition was very recent when I decided the lathe part of the 3-in-1 was pretty nice, but swapping between the mill and lathe functions requires a bit of set up time, so a new mill it was. I bought a PM-728VT. Now that is a nice mill!

The first thing I made on the 3-in-1 years ago was a small pin ball valve engine. Looked pretty nice but of course didn’t work. I made a lot of parts for car projects and other things, and then tackled a low temperature stirling engine (the Miser). This was made almost exclusively on the 3-in-1 so it is capable of good precision. And the most surprizing thing was, the engine actually worked the first time I set it up on a cup of hot water! So with that mastered, time to move on to something more challenging….the Little Demon. This has been going on now for a few years but I’ve recently gotten more serious about working on it.

I try and do as much on the CNC as I can, and here is my reason for this. First, I don’t always feel like being in the shop, so working on the computer doing the modelling and programming is still working on the engine without being in the shop. Second, when machining something there is a decent chance of doing something wrong; at least with me there is. By modelling and programming first, I can see what is going to happen before doing the machining. This is important for parts with many holes. A bit more on this later. Also, I still get a kick out of watching the machine do the work.

Please feel free to contribute to this thread if you are making a Little Demon, or any engine with similar parts. Particularly if you have hints and tips that could be useful to others.

I’ll start it off now and give you an idea of what this will be about. Oh, first of all here are the parts I’ve made or partially made so far. Block, carb, air cleaner, distributor, bell housing and adapter, crankshaft, connecting rods, water pump, oil pan, flywheel, rocker covers. Heads are in-work.

Well, this has been a longer intro than I expected, so the more interesting stuff will start with the next posting.

Rick
Hullo, would you share the gcode for these parts I am making one also have put up some pics on here somewhere Cheers Peter
 

xpylonracer

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Hi Rick

Please advise which material code did you use for the crankshaft and what is the diameter of the main and offset journals ?

xpylonracer
 

Carbuilder

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I followed the plans and used 1144 steel for the crank. The main journals are .373 dia and the offset ones are .248 dia. The diameters are from the plans; mine are not exactly that, but I adjusted the bearing sizes to match what I ended up with.
 

Carbuilder

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Here's another one along the lines of not wasting material.

I thought the bell housing would be a cool piece to make with that nice curved profile. I needed a piece of aluminum 2.5" diameter. I had lots of 2.25" and lots of 6". Obviously one was too small and I really didn't feel like taking half a day to turn a 6" chunk into 2.5" with mountain of swarf. Kept looking and found this piece.

Screen Shot 2022-01-05 at 12.31.33 PM.jpg

I got this from work some time ago when they were cleaning out a lab. It's aluminum, but not sure what type. BUT...it obviously had a large hole in it. Since the rear of the bell housing is not structural, I used this piece, machined the hole to an accurate diameter (around 1" since it was almost there), pressed in a smaller piece, and finished machining it. I was thrilled how it came out. Almost Clickspring precision!

Screen Shot 2022-01-05 at 12.32.44 PM.jpg

Screen Shot 2022-01-05 at 12.33.09 PM.jpg

If it wasn't for the different colors on the outside at the seam it would be pretty much invisible.

So a little bit of thinking outside the box when choosing raw material to use on a project can save time and find a use for that piece you picked up a while ago and couldn't really see a use for.

Rick
 
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I followed the plans and used 1144 steel for the crank. The main journals are .373 dia and the offset ones are .248 dia. The diameters are from the plans; mine are not exactly that, but I adjusted the bearing sizes to match what I ended up with.

Rick
Did you find a supplier in Australia for the 1144 steel

Michael
 

Carbuilder

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Since I'm in Canada, I didn't look for a supplier in Australia. ;)

I see that I didn't have my location identified. I'll correct that.
 

Carbuilder

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Making split journal bearings.

I've read about the method of soldering 2 halves of brass together, then machining the bearing. I thought I would try it without soldering, since it looked like the ER collet I use would hold the material just fine. Well, it does.

Screen Shot 2022-01-13 at 8.08.36 PM.png

Screen Shot 2022-01-13 at 8.04.27 PM.png

But, it does waste a fair bit of material since you need a certain length to hold in the collet. So I tried the solder method and figured the best way was to also solder it onto the end of a longer bar for machining.

Screen Shot 2022-01-13 at 8.05.27 PM.png

This worked well, but there is the layer of solder to deal with, even though I clamped the parts together for soldering. So when it was done and I de-soldered them and ran the mating surfaces over some very fine wet/dry paper to smooth out the remaining solder, the ID was just a bit under what I machined. I "massaged" it a bit to get it to fit. So both methods worked, but I would not say they were ideal.

I'm thinking that since the crank is supported on both end by ball bearings the journal bearings are to account for any deflection in the crank. I probably have a bit more clearance than I should in those bearings, but hopefully it will be OK.

Rick
 

Carbuilder

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I managed to ruin a few heads by not reading the drawings properly. Steve straitened me out. I thought the ruined heads would not really be good for anything since they were so full of holes, so not much usable material left. But...

My angle vice takes up a fair bit of vertical room, so if I put that in the small CNC mill it doesn't give much Z axis clearance. The normal small machinists vice fits much better, but of course doesn't hold parts on angles....or does it...

I took 2 of the ruined heads and milled a groove in each at an 18 degree angle and that works perfectly to hold the heads for milling the rocker cover area.

Screen Shot 2022-01-15 at 7.28.36 PM.png

I do a lot of engraving on the CNC mill (making custom car badges and stuff like that) and some of the cutters I use work very well for spot drilling for small holes. This type not only works great for engraving, but also for spot drilling the many, many holes in the heads. This is 1/8" diameter shank, 60 degree point.

Screen Shot 2022-01-15 at 7.30.11 PM.png

I did finally get a pair of heads done. Only have to drill the intake and exhaust ports and they will be finished.

Screen Shot 2022-01-15 at 7.29.12 PM.png

Screen Shot 2022-01-15 at 7.29.43 PM.png

Starting on the intake manifold now.

Rick
 
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I managed to ruin a few heads by not reading the drawings properly. Steve straitened me out. I thought the ruined heads would not really be good for anything since they were so full of holes, so not much usable material left. But...

My angle vice takes up a fair bit of vertical room, so if I put that in the small CNC mill it doesn't give much Z axis clearance. The normal small machinists vice fits much better, but of course doesn't hold parts on angles....or does it...

I took 2 of the ruined heads and milled a groove in each at an 18 degree angle and that works perfectly to hold the heads for milling the rocker cover area.

View attachment 133053

I do a lot of engraving on the CNC mill (making custom car badges and stuff like that) and some of the cutters I use work very well for spot drilling for small holes. This type not only works great for engraving, but also for spot drilling the many, many holes in the heads. This is 1/8" diameter shank, 60 degree point.

View attachment 133054

I did finally get a pair of heads done. Only have to drill the intake and exhaust ports and they will be finished.

View attachment 133055

View attachment 133056

Starting on the intake manifold now.

Rick
Nice work on the heads
 

Carbuilder

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I made the intake manifold. It certainly looks complex from the drawings. I found that I had 3D modelled it in Fusion360 some time ago...forgot about that. So having that model I decided to CNC the upper surfaces of it.

I added rounded corners to the outside of the runners to give it a bit of a cast look. Most of my CNC work I do with VCarve. I also have Desk Proto which I haven't used much, but decided to give it a try here. I machined the blank with the angled sides before deciding to CNC the rest of it.

I used 2 future holes in it to secure it to a waste piece of aluminum. The holes are counterbored for screws that thread into the waste piece. The holes are undersized from what they will be in the finished intake, so it's not like they are something I have to fill later.

Screen Shot 2022-01-22 at 8.27.31 PM.png

I used an 1/8" flat end mill for the rough passes, and then an 1/8" ball nose end mill for the finish ones. I took slow cuts with a fair bit of overlap, so it took a long time. Really pleased with how it came out.

Screen Shot 2022-01-22 at 8.26.50 PM.png

I still have to go back to the heads and finish the drilling of the intake and exhaust ports.

Rick
 

Carbuilder

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I've got one of those cheap little all-in-one sand blasters but never tried it. A friend with one said it works very well. I really have to try it one of these days.
 
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