PeterE Tries to Build a Trojan ...

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PeterE:
Hi Nick,

The Trojan is supposed to be easy and as far as I see it will not be difficult by being complicated, just that I am still not very much experienced with metal machines and different materials. I hope it will turn out good in the end.

I have actually seen both setups, the angle plate on the face plate, as well as the 4-jaw setup. I have tried both and the first time I used the 4-jaw it just came out good. The risk of marking the faces with the chuck jaws is of course present, but I don´t force the jaw screws that much nowadays as I did in the beginning, it works well anyway.

Using two angle plates on the face plate like a vice-type setup would of course be even more rigid.

Doing it in the mill instead would probably be just as good. I will use that kind of setup when milling the ports so then we will see where it goes.

Time to read the next section and proceed with the machining ...

BR

/Peter

Rob.Wilson:
Following along Peter :thumbup:

Looks like your making good steady progress :clap: :clap:

Rob

PeterE:
Good and steady progress, well I do not know really, I definately feel like a beginner with this.

First I made the top end cap from the supplied casting. It had a cast-in spigot so it could be gripped in the chuck and that way the "inside" towards the cylinder bore was made. Carefully approaching the fit diameter of the cylinder I succeeded to achieve an easy fit without slop. :D

Turned the cap round to remove the spigot and take down the thickness to drawing measure. Succeeded with this as well but "re-designed" the cap to become domed instead of just "cut off". Worked out fine so far. :D

Then marked out for the six fasteners and now I got into problems. The marking out was OK but after drilling the first guidance holes, one of them was misplaced as the tip of the drill decided to walk outside of the punch mark :bang: OK It was a pilot hole and as this is the first engine I can live with it :doh: When then trying to chamfer the holes using a countersink bit, the bit grabbed the cap and threw it out from my vice = one hole destroyed :bang:

Heavy sigh, :Doh: if I shall save this I have to think a bit. Will be back on this. Perhapsd I decide to redo the cap as I have a 10 mm thick brass flat bar.

Well I turned my attention to the bottom cap instead. It also had a cast-in spigot to use, which I did. The same first stage went fine and I managed to achieve the same nice fit in the cylinder with this cap. When it all was set up I drilled all the way through for the piston with a 4 mm drill. Now the casting is made for the bottom cap Mk 1 which means that it is necessary to remove some of the casting to make room for the Mk 2 piston guide (tube). Also this went fine even if it was thight for space.

I made use of my newly made tailstock support using the smallest center in the 4 mm hole, worked well. I also found that well sharpened and honed HSS tools were actually better for this soft gunmetal than the usual triangular carbide inserts. It should probably be those aluminium tips instead, they look sharper than the ordinary CCMT bits.

Anyway, it went fine and I could come to measure and cut off the spigot as intended. Time to open up the 4 mm hole to 5 mm to make the packing gland nut thread. As I work in metric I went for M6x1 which was OK up to the point where I tried a screw for fit, new disaster :bang:
It turned out that the cap had tipped in the vice when opening up the 4 mm hole and becoming angled instead if straight along the center axis. I did do the other holes in the bottom cap and they went fine all of them.

So, after today I have two half-ruined bits :bang:

Now I am thinking of how to save these errors so I don´t have to get new bits. :scratch: I can of course make plugs from the left over spigots and solder them into the respective holes and then re-drill and tap as required, but I am not sure this is the best way forward.

BR

/Peter

saw:
Peter, wellcome to my world. I have done this a couple of times and it is not so fun, but the fun part is to calcylate how to cheat it together so it looks really out.
If I was you, I would use my lathe and turn some piceses that fits that holes and solder them together, and then do a fresh start.
About the bottom cap, why diden't you use youre lathe to drill the hole. If you set it up correctly you are garanti that the hole and the threading will be in the correct line
Otherwize I think that you are doing well. :D

PeterE:
Hi Saw/Benni,

Thanks for comforting words, I guess I am not the first to goof it. When it comes to the holes in the top cap it is really a question of whether I want to keep the gun metal casting or make a new cap from brass. If I decide to keep the gunmetal one, I will go the way you describe by making plugs and solder them in place.

The bottom one is trickier actually as the supportive spigot is not possible to use as this is where the hole and thread shall be placed. My first thought is to use one of the left-over spigots and turn a short piece of spigot and thread with M6 and solder it in place. Then re-drill the 4 mm hole properly in line and then in some way try to turn the cap and open up and thread again. Another way to do it is to set it up in the lathe and open the bad hole to a plain 6 mm hole for threading using a "french" M7x1 thread instead. This is for the gland nut so it is a one-off anyway and the odd thread does not matter.

Coming to think about threads, All the drawings state imperial ME threads typically 1/4"-40. Normally I would happily translate them into metric, but a -40 thread would translate into 0,5 mm which is not a common one = expensive. Just because of that I wonder if I shall go for the stated ME threads instead?

BR

/Peter

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