WT2527 15cc Glow Engine

Hi Neil,

Thanks for the comment. I did think about bearing lubrication when ordering but came to the following conclusion, these are sealed units (for life), life expectancy standards (without going into the full calcs that seem to be available) could be 300hours at a minimum, ranging at to the thousands of hours.

IF I do get this engine to work and put it in a plane, I would on average have the engine running for 15hours per year.

So taking worst case I would still get 10-20 years out of it. I'd be very happy if that was the case.

Do you have a drawing that shows the principle you describe above? Even though the part is finished now I reckon I could still get a lubrication channel behind the back bearing, and I'd be keen to understand for other engines.

Here is a sketch of the added seal area. The gap is showing the small clearance, and will be a solid fill, I just drew an out line.

Neil

Thanks for that Neil, if I understand correctly the lubricant wicks to the front bearing via the annular gap between the shaft and clearance made (0.03mm). As you say obviously too late to have that arrangement on this model, but would a fully open inner seal work, i.e. if I just remove the inner seal on the front bearing and make a small channel or two behind the rear bearing?

also made a bit of progress on the main crankcase today. Was a lot of work to get the 70x70mm stock down to size (45x46, plus the mounts), but got there in the end, ankle deep in swarf. Now starting to work on the mounts.

a bit more progress today. Turned the cylinder, cut the fins (1mm fins/2mm spaces), and bored out ready for liner.

Nice work - looks like you are making good progress!

Good progress Craig​ ,neat finning , what do you plan to put it in for its first flight? Trevor

Thanks guys. Trevor, after bench running I'll throw it in a trainer until I'm sure of its reliability. Then it's for a 1/7th scale scratch Spitfire I'm building. Failing that I have a Laser 100 in the cupboard ready.

Had a few sneaky days off while I built a kit set radio control car for the kids (well me actually).

Next on the engine was onto the rotary table to mark and drill out and tap the four 4 mm fixing holes front and rear.(I did use a centre drill first).

Using a piece of scrap I made a holding jig so that I could put it back in the lathe to bore the tangential hole.

Then back onto the rotary table to trim a few corners. I think what I'm finding now is that I'd wish I spent a little more on the next size up mill. Mine is a WM14 with 280mm spindle to table distance. Even with the smallest rotary table I could find I do struggle for space with some of the setups.

Crankcase pretty much finished with exception of trimming the rear corners once I make the rear crank housing.

Very nice work. Amazing what you find hiding inside blocks of metal isn't it.

Well it's been a while, been spending the summer with the radio control planes and also working on the spitfire.

With the wet weather decided to make a start again. Something simple and small to get back into the swing of working with metal rather than balsa. The rocker cover seemed like a good place to start.

Edited By Craig Booth 1 on 26/08/2018 21:14:19

Made the cylinder liner. Had some problems with boring the cylinder and getting a nice finish which I suspect was down to my lack of experience but possibly also the EN16M material which I understand is slightly less machinable than EN8. Perhaps I could have just used EN8 for the liner?

Anyway seem to corrected the problem with a lap and now all seems ok.

I also have EN16 for the crank, but if it is going to be that hard to machine then may look to change. Any opinions? Would EN8 suffice?

Also started making the blank for the cylinder head. That is going to be the hardest part for me to date. Plans look pretty complicated with plenty of angles and different steps. Trying to break it down into the right sequence.

I have made the block and cut the part that sit in the top of the cylinder liner. I have then made a mirror jig of that out of aluminium 40mm bar. This should locate the jig exactly centre. Next I will drill the head bolt pattern using the mill and use those to fix securely to the jig. All other steps can then be carried out using the jig to hold it.

I am relying on a new Mill I have on order to help me. I currently have the WM14 but have been struggling for vertical space once i get the rotary table on, so have decided to upgrade to the WM16 and have also ordered a DRO set. I am hoping this will give me some better accuracy on my mill work.

(PS if anyone wants a WM14, 7 months old, little use, let me know)

Here she is so far side by side with a Laser 100 which is currently destined for my Spitfire which is currently competing for my time.

Edited By Craig Booth 1 on 30/08/2018 12:49:53

Had a new toy to play with today. A new WM16 mill with DRO. What a difference having a DRO makes.

Used it for the first time to to do some more work on the cylinder head.

Learnt two lessons today. One - spend more time reading the plans, two - use lubricant with a slitting saw.

You can see the mistake on the first fin at the bottom of the cylinder head. Was supposed to be a 1mm fin at bottom, not 2mm. And the second fin is less than 1mm due to the slitting saw ripping.

Fortunately these are only cosmetic, but a bit annoyed with myself.

Edited By Craig Booth 1 on 08/09/2018 21:15:54

and today milled the cylinder head slots for the rockers.

That all looks brilliant. I shall be watching for updates

Very Good Work Craig! A lot of intricate work on the cyl-head - very nice indeed. I seem to only ever make tooling or machines or parts for machines or upgrades for machines.... Am very much in awe of the type of work accomplished by chaps like you!

Very keen to 'hear' a video of it running! Nice going.

Joe

Great that you can take pictures as you go, I always forget, or don't have my phone handy etc. Don't have my phone in the shed when making parts, that way I don't get distracted. Looks really nice and coming along well. Looking forward to the video of it running. That will be real music to me.

Neil

Agree with everyone, great craftsmanship. You appear to have a very wide range of skills, the spitfire looks superb. Keep posting Craig, really interesting topic.

If I was betting man I'd say you probably laid that patio as well......?

Geoff

Hi all, thanks for all the comments, much appreciated.

Over the past couple of days I've been working on the exhaust valve (SS316) and valve liner (Colphos).

The plans call for an OD on the valve liner of 13.5mm, and therefore obviously the same size hole to fit in the head. I looked at a 13.5mm end mill but to be honest was scared away by the cost for something I will probably never use again, so have reduced the OD to 13mm. Hopefully it does not make too much difference to the performance. If my maths is correct it is a 7% reduction in area. Might be able to make up for it a bit by some port and polishing.

The valve liner will be an interference fit in the head.

My other cheat was the valve shaft hole in the liner at 3.5mm. Again I do not have a 3.5mm reamer and looked at prices and decided just to drill. Although the valve feels smooth in the liner, I'm just not sure. Any slop here and the exhaust gases will pass. Of course I did not think of a hand reamer which are much cheaper. So I think this set I've made will be put down as learning curve and practice and I'll re-do it properly once I get a reamer.

Edited By Craig Booth 1 on 12/09/2018 21:55:46

Wow. The match stick really sets things in perspective! Nice work.

For future reference, cheap but quite reasonable quality reamers are readily available, like this one here

**LINK**

two for $8.95 including shipping.

I have found them quite good enough for home hobby shop use.

Edited By Hopper on 13/09/2018 01:16:42