25 cc Horizontal Engine

[Don1966]

Still following Roger and I know about breaking the tip of center drill into my projects. It can cause a lot of grief. Nice save bud and nice work. 

Don

[Roger B]

Thank you Don 

Next I made a simple carburettor adaptor so I can use one of my dodgy selection of carbs for the first trials. This was turned from a piece of 12mm dia. brass set eccentric to give little more thickness for the grub screw. I was a little concerned about the eccentric parting off but it seemed to go ok.

[Roger B]

I cut some gaskets for the inlet and exhaust and then moved on to finishing off the valve seats. Unfortunately I had a 'Poying' moment and an E clip, valve spring collar and valve spring departed to the land of the swarf gnomes    I actually found the E clip but no signs of the other parts  I have ordered some new valve springs and decided to make two new collars, just in case.

[Roger B]

The next bit was an M8 x 1mm plug for the waterways in the cylinder head. Having looked at the price of an die I decided to cut the thread in the lathe (I also needed a length of M8 x 1 brass for another project). I first made a steel test nut and then turned the plug from 12mm dia brass. The threading, under power, was a bit dubious  but I found that if I pressed the stop button as soon as the tool contacted the work piece it stopped before hitting the end.

I don't have a dividing head or spin indexer so I tapped a bit of hex bar M8 x 1 and used this to index the hexagon. As long as the milling forces tighten the thread it should be ok. As it was a little job I used my Proxxon drill to mill the flats rather than converting the lathe.

[mike mott]

but I found that if I pressed the stop button as soon as the tool contacted the work piece it stopped before hitting the end.

Wow that sounds scary, Roger is it not possible to cut the thread by turning the headstock by hand? I have had great success working the threads by hand on my Myford I just make sure I unplug the lathe first, those automatic reaches for the on/off switch have caught me off guard a few times over the years, so now i always unplug the lathe when rotating the headstock by hand. The other advantage would be an even speed.

Mike

[Don1966]

Nice going Roger, she sure looks the part and thinking outside the box. 

Don

[Doc]

Unfortunately, possibly due my laziness in not increasing the speed the centre drill broke on the second hole 

I kept going, planning that if I kept the two weights in alignment I could realign them from the other side and drill through, pushing out the broken tip of the centre drill.

The slot was carefully opened either side up in small steps, always conventional milling, to keep everything square. I had an offcut from the crankshaft to use as a gauge.

Luckily I was able to successfully drill through from the outside and remove the broken bit of centre drill    The two hole were then counter bored for cap head screws.

Here is a simple way to remove a broken center drill tip. Take the cdrill that broke and grind half of it away and then use it to simply treepan it out.  Attached is a photo of what I'm talking about. I have use this a few times and it works like a charm. It will cut a groove around the broken tip and it will just kick it out.

[Roger B]

Thank you all for your interest    I think that a handle for the headstock must move up the list of things to make, there is quite a lot of run on after the stop is pressed.

I like the idea of the trepanning tool for broken centre drills    I hope I don't need it again but it's definitely good to know 

[Roger B]

The next step was to make some nuts and studs for the inlet and exhaust. The nuts are M3 made from 5mm hex brass and are 4mm high.
I got some good quality 12mm diameter M3 dies in a sale a while ago but did not have a suitable stock so had to make a quick adaptor for my tailstock die holder.
The studs are made from 3mm stainless steel and the new dies cut it as though it was brass (just as well as the straight section in the middle is only 3mm long).
I decided to make a spare stud and nut just in case the swarf gnomes were active today.

[Roger B]

And assembled 

[fumopuc]

Hi Roger, looking good. First pops are not far away anymore.

[Roger B]

You were right Achim 

As the sun was shining I fitted it to the baseplate from the original, wired up the ignition and took it outside.

It fired as soon as I opened the needle valve enough  but the exhaust valve started leaking a little so it would not run properly. Not bad considering I haven't made and fitted the piston rings yet 

<a href="https://www.youtube.com/watch?v=hXk1ADS2zLQ" target="_blank">http://www.youtube.com/watch?v=hXk1ADS2zLQ</a>

[Jo]

  Well done Roger.

Jo

[Stilldrillin]

Very nicely done, Roger. 

Congratulations on the first signs of healthy life.

Where would we be, without a few teething problems! 

David D

[Admiral_dk]

And we have the first pop's  it can't be far from sustained runs