Poppin Engine build.

[ian_in_the_midlands]

Following people kind enough to answer my questions, and requesting I do a log of the build, here it is.

Be aware - this is not a "how to". I have no idea what I am doing as I have only owned a lathe for a couple of months, and the only engine I have built so far is the simple Elmer's wobbler.
I am using the poppin as a project to learn about machining, so any constructive comments will be welcomed.

First the pictures of where I am now.
The cylinder and cylinder head are finished, and the piston has been made.

My first attempt at lapping the cylinder by hand ended in disaster with the centre becoming a larger diameter that the two ends.
I used an adjustable reamer, taking very light cuts to get back to a cylinder. I then turned the piston to be a tight fit, and brought it down to size using very fine abrasive. It is now a lose but airtight fit. In the picture the cylinder looks quite rough, but I think this is an optical illusion. I will wait to see if the engine runs before trying any lapping again.

[ian_in_the_midlands]

This afternoon I started on the crank.
The plan calls for 7/32" x 1/4" steel.
I had some 1/4" key steel, so this was faced down in the lathe to the size required.
This was then sawn in half, and marked out.
The holes were then drilled in the lathe with the two parts held together in the chuck. The holes will be reamed to final size when my reamer arrives next week.

I plan to silver solder the crank parts together - something else I have never done before.

[dawesy]

Looking good. Must have a ho at something like this.
Keep up the good work ;)

[Stilldrillin]

Hi Ian.
Watching.... Reasonably quietly. 

How did you lap the cylinder? I often find mine are slightly small, in the middle...... 

David D

[ian_in_the_midlands]

For the attempt at lapping that failed I made an aluminium lap, and using fine grinding paste, held the lap in the drill at slow speed, and held the cylinder in my hand, trying to feel for tight spots.
I had read there is a danger of opening out the ends too much. That is probably why I concentrated too much in the middle.

After correcting the problem with an adjustable reamer, the piston feels a constant fit all the way through.

[dawesy]

Myfordboy on you tube did a video on lapping a cylinder.
If this one needs it (though it sounds like you've got it spot on) it could help.

[Stilldrillin]

This is my method.

Piece of dowel. Minus a thou or so, on bore size.......




Smear of fine grinding paste. Plus oil, as time goes on. Around 80rpm.......




The cylinder is oscillated backwards n forwards. Reversing occasionally on the lap. Until all feels smooth with no tight spots.

Works for me! 

David D

[ian_in_the_midlands]

I have seen the video from myforboy where he is lapping a cylinder. One of the few videoes I could find showing the lapping actually being done. I have watched and enjoyed alot of his videos. If I find I do need to lap the cylinder I will try your method David. Thanks. Before I do that though I may polish the cylinder a little using the piston. What abrasive,  if any would I use for this? I do not want to risk anything that might embed itself into the cast iron. Someone recommended tooth paste but that seems a little course.  I thought maybe just using oil or possibly powdered chalk?

[lordedmond]

Fine grade Time Saver powder is the bees knees for laping

It breaks down during use and becomes none abrasive , it can and is used in industry to bed in gear boxes the fact that it breakes down meand that the gear box will not need dismantling for cleaning

I will get a link

Here you go

http://www.steamsupplies.co.uk/category/engineering-supplies/sub,36/30/1/0

Stuart

[gmac]

And a booklet to go with it.....

http://www.newmantools.com/lapping/timesaver_booklet.pdf

You made me go looking.....

Cheers Garry

[ian_in_the_midlands]

A bit more progress today. The second pair of holes were drilled and reamed on the crank. I couldn't align the bars together in the lathe so had to use the drill press. Took ages to get everything right, but everything looks parallel and square. Back on the lathe to radius the ends and turn to length. I was careful to use very light cuts for this one.
Finally a quick rub on a coarse diamond stone to remove the chuck marks, and parts are put together while I decide how I am going to fix them.

[ian_in_the_midlands]

I now need to decide if I am going to threadlock and pin or silver solder the crank together.

If I go with threadlock and pins, is the grade of theadlock important, or will any do?

As I have not silver soldered before, I thought it prudent to do a practice bit first.

3 holes drilled and reamed in some key steel.
1 left like that, 1 chamfered, and the third chamfered with some grooves filed to help the solder to wick up.

I will see what I can do tomorrow

[Stilldrillin]

Ian.
I prefer Loctite 270, (any will do, I guess), plus 1mm dia cross pin.

Have a look here. About half way down the page....... http://madmodder.net/index.php/topic,8821.0.html

The m2 grub screw, locating into a dimple. Allows dismantling, and accurate re-assembly.

Still going strong! 

David D

[dawesy]

Coming along nicely

[ian_in_the_midlands]

My first attempt at silver soldering was not good.
I has trouble getting the solder to melt and flow.
I had carefully cleaned and degreased so suspect I had not used enough flux.
3 pictures below are the results after a rub on the diamond stone, the results after a savage attack with a hammer, and a shot from behind showing the solder had wicked through the filed slots.

Although the first two pins did fail eventually, they took some abuse before they gave. I can see little or no evidence of solder, but surely the oxide can not hold that hard?

The third joint held firm, but does not look very good as the solder had not flowed around the chamfer.

Loctite 2700 and 1mm steel for pins have been ordered.

[lordedmond]

Not hot enough
Or burner not big enough, you really do need propane butain is ok for small jobs

For the low melt SS you need a good 650 deg C or a dull red but it must be all up to temp.

Remember the SS will flow towards the heat , therefor you controll the flow

As a final point flux I use T5 it stays active longer in the heat and is more aggressive as a result when the joint is hot enough the flux will go clear and the joint will look clean, yes it's a bit harder to clean up but a soak in citric acid sorts it out

Stuart

[ian_in_the_midlands]

A bit more time in the garage this afternoon, making the cam washer and two flywheel hubs. I will have to wait for the die to arrive before I thread them. A good chance to try out my new collet chuck. Don't know how I managed without one before.

[ian_in_the_midlands]

More work on the crank.
Assembled with green threadlock yesterday. That stuff doesn't give you much of a handling time does it!
My plan today was to drill through and threadlock in some 1mm pins.

Confident this would be okay after doing a test piece, I managed to snap a drill off in third hole.

Managed to drill/bash the broken bit out, but it all looked a mess once I had finished.
A change of plan. The holes were opened out to 2mm and the both ends were countersunk by a small amount.
Panel pins were cut to length and peened to fill the holes.
The sides were then flattened off using a diamond stone.

Not perfect, but disaster avoided. A shame I am a poor shot with the hammer as I have left some small marks on the edges.

[lordedmond]

Ian
At the risk of telling you how to suck eggs , when you cross pin webs do not countersink or do any work on the hole edges that way when you press in the pin and dress it off it will not be seen .

Stuart

[ian_in_the_midlands]

That is the sort of advice I am on here for Stuart.
Too late for this one, but I will know next time. Thanks.

Centre now cut out and filed flush.
I think I have got away with it.

[ian_in_the_midlands]

Progress today: Hubs threaded, and two nuts made.
Picture added of parts assembled.

I also made a guide that will hopefully allow me to drill holes that match in the cylinder head and the standard.
My method of determining the placement of the 4 holes was to used a punch mounted in the tool holder, making a mark horizontal with the centre then and rotating the piece 90degrees. The correct rotation was determined using a square. This was repeated 3 times.

When the holes were drilled they aligned with holes already drilled in the top of the cylinder head, so my strange method must work.

Any suggestions for a better method I could have used?

[ian_in_the_midlands]

What bearings should I be using?
As the shafts are 4mm, I was looking for 4x8x4, but can't find any.
I could use the bearings in the picture?
They are slightly larger diameter at 4x9x4, but I can increase the size of the standard to cater for this.
Would these be good enough quality?
Would I have to remove the shields to lubricate them?
Will they work with the shields removed or would they simply collapse?

[Stilldrillin]

Ian.

I would use the 4x9x4, with the steel shield in place.

Occasional lubing with light oil, will penetrate. No problem!

This is what I use, for this kind of purpose..... http://www.ebay.co.uk/itm/50ml-Ballistol-Universal-Lubricating-Maintenance-Oil-for-Shooting-Fishing-DIY-/380659885378?pt=UK_SportingGoods_Hunting_ShootingSports_ET&hash=item58a118e542

David D

[ian_in_the_midlands]

I moved onto making the cam today. I started off with a mild steel bar of 28mm diameter.
The end was faced off, then I cut off 1.5mm. This was turned around in the chuck and an 8mm hole was drilled and reamed in the centre.
An 8mm mandrel was turned and my new "washer" was threadlocked onto it.
This allowed me to face to width and turn it to 1" diameter.

I then made a guide of 0.6" diameter into which I could screw the cam. Using a grinder/file/diamond stone, a flat was made that just met the guide.

I had no way of measuring angles directly, so I measured a chord of 20.81mm from the end of the first flat, and ground/filed/stoned a second flat up to that mark. This gave me the angle I needed (if my maths is correct).

The waste was then removed all the way around up to the guide. I then finished off with some emery paper.
I don't think the results look too bad.

[ian_in_the_midlands]

Today I made a start on the flywheels.
I turned some 2 1/2" brass down to 2 1/4" - leaving it 1/4" oversize. Two disks were cut off and faced to width.
The centre recesses were bored, but left a little under diameter. A centre hole was then drilled and reamed to 8mm in both wheels.

I made a mandrel out of aluminium. The plan is to keep the mandrel in the chuck to ensure concentricity, and use this to hold the flywheels, take them to the to final dimensions.
I used aluminium in the hope that it will mark the brass less than steel would, but I have some concerns that it may not be strong enough.
I will make up my mind if I use it or not tomorrow.