1/4 scale V8, first project.

[2CYL4STROKE]

This is so beautiful piece of art

 

[agmachado]

Hi Keith,

I understand you... Let me help you to document your project. My workshop is not complete yet... I have only a small lathe and some tools, gradually I will buy a small mill and other tools to build my first I.C. engine... but now I would like to make something and maybe I could create the models in a CAD system and after, the drawings of each part.

I can start from your sketches or drawings and slowly we go clarifying the possible doubts. I can use SolidWorks 2010, because I have more facility to use.

Would be a pleasure help on this project.

The posted pictures are very cool !!!

Cheers,

Alexandre

 

[LongRat]

Great to hear you are in the UK. Your engine is looking more incredible by the day. I really hope you are planning to exhibit it at some of the UK shows.
May I ask where you get the low melting point alloy?

 

[Brian Thomas]

This thread is just too much to take in. Very nice work.

 

[keith5700]

Sorry about my slow responses, I get sidetracked all the time with other jobs.
Longrat, I acquired the alloy from work years ago, no-one can remember where it came from. It is available on line, but it looks quite expensive.

I've made the flywheel and ring gear. As I couldn't fit my original flywheel design in, due to the closeness of the headers, I designed a smaller one. I want this engine to have a slow tickover, and have a realistic overrun, so I needed a heavy flywheel, which the original was. With the small diameter of this one I made it out of tungsten alloy, which is very heavy. I think it's about 2.5x heavier than steel.
Before anyone asks, I don't remember how I got it, but it's been sat around for years waiting for a use.

It was horrible to machine, blunting the carbide lathe tools, and snapping drills. But it feels great when spinning on the crank. The pattern in the middle is for a starter drive before I get the proper electric start made.

Next pic is my lash up to bore out the camshaft bearing/seal holders.

This is a pic from today showing it's not all shiney bits and glamour. I've got bits of stuff all over the place at the moment. I have no overall plan,so I'm going in all directions at the same time.

This shows pickup pipe from sump to oil filter.

I've finished the pistons and made 4 liners so far. Need to figure out how the finish bore the liners, my lathe won't hold a thou' over 1.5".

Today I've been 'o' ringing the heads as I hate gaskets. The only gaskets I will use will be the head to block joint, as there's too many holes to ring.

 

[suprspooky]

Hi Keith,

I'm a new member and just wanted to say how incredible the Engine is , I've done a little machine work with a Bridgeport and it is astonishing to see such intricate work being done on a non-CNC machine. Truly amazing!

Have you thought of using a Brake Wheel Cylinder Hone to finish your liner bores?

Your humble admirer,

Dave

 

[keith5700]

Time for an update I think...
Been trying to sort out the cams and valvegear, and it's been doing my head in.
Think I'll make a vee twin next time!

I hogged the cams out on the rotary table, using cuts at 5 degree intervals, then blended the flats in with a file.
They didn't look too bad but I wasn't 100% happy with them, so I decided to grind the profiles to get them spot on.

After hardening the cams I started making a makeshift copy grinder attachment for the lathe.
This seemed to take forever, but the results were worth it.

I made a full size cam lobe and then designed the linkage to move at 1/4 movement.

Some pics of the grinder, coplete with novel belt tensioner (weight hanging off a bearing race)

This is part of the full size cam follower, which is 4 x the diameter of the grinding wheel

Machining a valve

Valve components

Cams, before and after grinding

Fuel injector from Fiat Punto

 

[keith5700]

The valves may look a bit unusual. This is my solution to the problem of creating a hydraulic oil lock under a conventional bucket type follower. The valve stem is also the sliding part of the follower. The tops of the valves are screwed on after the springs are installed.

The fuel injector is quite small, and rated at about 20 hp per injector. I'm hoping one injector will run this engine. It came apart ok, and the coil is useable, if I can get some wires soldered onto it, after cutting the massive connector off.

The injector orifice is 18 thou' diameter.
Rather than trying to work out what orifice I needed, I decided to see what the smallest hole I could drill was.
I bought some solid carbide circuit board drills, and tried to drill some silver steel (drill rod)
The smallest practical hole on my slow spinning lathe was 10 thou'

The drills worked perfectly, and the holes were spot on.
Took about 1/2 hour to get 2mm depth though.

More pics to follow on injector design later...

Dave, yes I will get hold of a cylinder hone and have a play with it.

 

[Mosey]

Keith,
As I learn more and increase my skills, I like to think I'm making progress up the ladder. Your engine has just shown that I am apparently much lower on the ladder than I imagined. Your work is spectacular! Keep it coming. If this thing sounds like I expect from the pictures, they will take me away quietly.
Thanks for sharing.
Mosey

 

[gbritnell]

The extra work on the cam grinder paid off. The cam looks great and with it being hardened it should last forever. Novel idea on the valve setup. I'll keep that in mind.
gbritnell

 

[LongRat]

Yes, I love that valve idea. When you say you made a full-size cam lobe, how exactly did you do that? Normally when people make these scale reducing copy grinders they use a commercial cam to copy.

 

[keith5700]

Yes, I love that valve idea. When you say you made a full-size cam lobe, how exactly did you do that? Normally when people make these scale reducing copy grinders they use a commercial cam to copy.

My first idea was to copy a commercial cam, and I had a Chevy V8 cam cut up ready to mount in the machine.
Then it suddenly struck me that it wasn't going to work, because the Chevy cam goes through a 1.6:1 ratio increase, on the rocker arm, before it opens the valve.
My cam pushes straight on the tappet, so there is no increase.

So basically the lift from the Chevy cam is 1:1.6 too small, relative to it's base circle diameter.

I went back to the cam I'd drawn up, with the help of CamCalc, and just scaled that up 4x. This is a free online cam profile calculator, which gives lift figures at various angles.
The lift figures are of course the same figures which you would move the milling table when cutting a cam in a series of flats, using the rotary table method.

I will reserve judgement on the valve idea until I see it working, or not.
The only downside I can see at the moment is that there's no way to adjust the cam/follower clearance.
The initial setting will be fine as the tops of the valves will be cut to length. When/if the clearances increase, due to wear, etc. then it gets a bit tricky to reduce the gap.
I'm still pondering this bit, before I actually fit them.

 

[mu38&Bg#]

The tappet clearance will be adjusted just like any other bucket follower. Put shim washers between the follower and the valve stem, and reassemble. If you didn't see this as a option initially, it might not have been obvious to leave some extra clearance, so that a shim is required and allow you to enlarge the gap by fitting a thinner shim. I like the concept. Even though it makes for heavier valves, I doubt you'll be running fast enough to have problems with float. Camcalc from modelenginenews.org?

It will be interesting to see the injector.

Greg

 

[keith5700]

Greg, yes, the obvious method is to shim between the valve and follower. As I've been pondering it though I've been considering how I'm going to get small washers of, say, 1 and 2 thou' thickness.
The answer is, of course, set the valves to use a 20 thou' washer from the start, and then work from there in the future. Bit of brain fade on my part I'm afraid.

Yes, CamCalc was on that site, but I'm unable to open it now. Don't know if it still exists?

And as you say, the weight of the valve will not bother me. I want a low revving slogger. The top speed is of no interest to me really. My goal is to get it to tick over at a really stable 800-1000rpm?
Time will tell. That may be complete cobblers.

I'm starting the injector at the weekend. I'm also interested to see it evolve. I'll try and get a drawing up here, in case anyone has any thoughts before I start cutting metal.

Cheers, Keith

 

[crankshafter]

Keith.
If you need small dia. shims ask at a shop where they servicing dieselengine injectors ;D or I can send you some.
And here is a link to the CamCalk:http://modelenginenews.org/design/CamTable.html

CS.

 

[keith5700]

Thanks crankshafter, but I'll need the shims to be small washers, 6mm od by 3mm id by 20 thou' thick nominally.

Here is an assembly drawing of my proposed injector. The blue bit is the original coil, turned down a bit, and the red thing is the pintle. All the rest is new. It's about 28mm long overall.
Fuel will go in and under the coil, up inside the coil and through to the centre of the magnet, then down into the pintle.

The magnet thing is threaded into the outer cap so I can fine tune the gap between it and the pintle.
There is a spring, not shown, which pushes the pintle down to close the injector.

Second pic shows the pintle sealing end.

 

[keith5700]

Right, the injector is now finished.

The trickiest part was trying to get some wires soldered onto the coil.
The original coil was turned down a bit on the o/d, and this left 2 coil wire ends sitting flush to
the outer surface.
I had to cut away a bit of the plastic, under the microscope, to reveal enough wire to
solder to.
If I make any more injectors I will wind my own coil. It will be a lot easier, and smaller too.

As I only need one or two injectors, and they will be hidden, the size is not important, apart from the height.
This injector is about half the length of the original, but about the same on diameter.

The other hard bit was making the orifice plate. I managed to snap 4 x carbide drills, .010" dia.
My test drilling went straight through some 2mm plate, but this plate is 3mm. I got to 2.8mm then snapped the drills
trying to get deeper. I gave up in the end and thinned the plate a little.

The orifice plate was then hardened and polished flat, finishing with 3000 grit paper. Hopefully it will seal on the pintle ok.

The injector clicks away merrily under power, so I now need some high pressure pump setup to test the sealing, and the spray pattern.

I thought about using methylated spirit as the test liquid. Any better suggestions welcome.

 

[LongRat]

Being somwhat more polar than petrol I would think the surface tension properties of meths would be very different. I think it would be a safer bet to test with the actual fuel you will use. Very nice work on the injector by the way. I wonder though whether the injector will work properly passing such a small amount of fuel, I would have thought 1 of these injectors for the engine would have been more than enough?

 

[keith5700]

Not much to report.
Had a bit of time off to get some other jobs done.

Managed to get all the valve components done and sorted all the shim washers out for the tappet clearances.
Then I started some more machining on the valve covers, to get some clearance for the oil feed pipes, but managed to put the cutter through the side of one of them. That was when I decided to have a break.

I've now made 2 new covers, which look a lot better than the old ones, so everything turned out ok.

Here's a couple of up to date pics, taken in a small light cube, which look loads better than just sat on the bench with a flash gun.

 

[gadabout]

Oh My G0........!
You're not from this planet are you?

in awe
Mark