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发动机建造 Kiwi Mk2(绝对精华)

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 楼主| 发表于 2014-4-24 05:23:44 | 显示全部楼层
This evening was spent thinking how to do the hole in the rear crankcase casting keeping it lined up with the hole in the front crankcase casting . Eventually I came up with an idea.
I located the aluminium I used to machine the timing cover and bolted it to the rear casting with the timing cover in place. I bolted on the front casting and did a trial setup on the rotary table to see if I have enough headroom under the mill chuck. Well there is enough headroom but I did not like the setup. I need to simplify it by removing the 1-2-3 blocks. I think I know how to do that.
The idea is to do the hole and mill the bearing housing in the same setup.

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 楼主| 发表于 2014-4-24 05:24:09 | 显示全部楼层
This morning I simplified the setup on the rotary table by removing the 1-2-3 blocks. I put them there yesterday for two particular reasons. The first one was that the screws I was using where not flush to the aluminium and secondly because that I thought that if the drill passed through it would hit the rotary table. Well both problems were solved. Bought new screws which fitted better the counterbore so the heads were flush and also realised that even if the drill went through it, it would still be in the centre of the rotary table hole.
I usually setup the rotary table using a MT2 taper tool (it is also used to hold things on the rotary table) that I made some time ago (first photo). I never bothered to check how accurate this method was, but out of curiosity I checked it with a dial and it was spot-on. I put the crankcase (with the aluminium plate) on the rotary table, and using the previously used homemade punch in a 10mm collet, I centered the crankcase and clamped it to the rotary table. I took the quill down into the crankcase and spotted the bottom part of the crankcase (where the hole needs to be drilled). Unbolted the front part off the crankcase and took it off and checked again that I am still lined up with the mark I just made.
Then I had a break. Snooze time.

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 楼主| 发表于 2014-4-24 05:25:12 | 显示全部楼层
This evening continued work on the casting. I am happy to say that everything went to plan.
Started off by centre drilling, drilling 6mm, 8mm and 9.8mm and then reaming 10mm. I did not use the drill chuck for these operations but used collets. Then I used 12mm, 15mm and 18mm slot drills to widen part of the hole for the bearing housing. Continued milling the bearing housing using an 8mm carbide endmill and the rotary table to get 18.995mm diameter for the ballrace. It was a bit of a pain retracting the endmill and checking diameter but it was worth it.
Now for the moment of truth. Took it off the rotary table, inserted the bearing, assembled the cranckcase and checked if a 10mm silver steel bar would pass from one side to the other. It passed and it turns.
What a relief. I think I have passed what in my opinion was the biggest hurdle in this build. Now to go back to Westbury's instructions.

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 楼主| 发表于 2014-4-24 05:25:39 | 显示全部楼层
Yesterday I went shopping for a pair of V-Blocks with clamps from a local guy. It's not a shop but a garage so i never know what's available. Well I was in luck he had what I needed and in two sizes. I got the large size and also bought a centre drill set (what I had was on its last legs) and an ER32 collet all for the princely sum of 70 Euros. Went to my shop and tried a trial setup for the next operation using the V-blocks on my granite surface plate.
Today, after work, I had another look at the setup and it looked sound and did some mesurements and markings. The next operation is to mill the cylinder platform. It has to be parallel to the crankshaft and 1.5" (38.1mm) above the crankshaft centreline. Using the 10mm silver steel rod going through the crankcase supported on the V-blocks I marked the 38.1mm line. Put everything on the mill table and clamped everything (v-blocks and crankcase).
I will do the milling tomorrow. This will at least give me a flat surface to continue work on the crankcase.

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 楼主| 发表于 2014-4-24 05:26:22 | 显示全部楼层
Today I milled the cylinder platform, but instead of 38.1mm above crankshaft centerline I did it 39.1mm above the centerline. Yesterday, I was re-reading Westbury's article and at one point he says:
"The distance of the cylinder platform from the crankshaft centre influences the compression ratio, in conjunction with the dimensions of other components. Some constructors may wish to produce an engine to run under load at relatively low speed-not more than 2,000 to 3,000 r.p.m., for instance-and if so, the compression ratio may be reduced, either by leaving more metal on the platform surface, or by fitting packings under the cylinder platform, which is more adautable but less positive.
Low compression is recommended if the engine is to be used for driving a heavy boat such as a tug or cargo liner; the beginner may find it easier to deal with, as it promotes docility and easy starting, and all adjustments are less critical than when the compression is high."
Problem is that he does not say how much more metal to leave, so I left 1mm more. I can always bring it down to 38.1mm at a later stage.
After that operation was finished, I inverted the crankcase and making sure it was parallel to the table, I milled the engine bearers (supports).

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 楼主| 发表于 2014-4-24 05:26:41 | 显示全部楼层
Just for fun I put the unmachined cylinder casting and cylinder head casting on top of the crankcase just to have an idea of how it looks.

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 楼主| 发表于 2014-4-24 05:27:23 | 显示全部楼层
I haven't been idle these last couple of days. I was making the engine supports so that it can stand on its own feet. I used a piece of aluminium flat bar that I had and milled it to size.
Yesterday I was looking at the two engine supports and was thinking that they look bland. I need to spruce them up a bit. Various ideas came to mind but the one which I sort of liked was to engrave the name of the engine on each support. Just one problem, actually BIG problem. I don't have CNC.
So I kept thinking about it and came up with a plan. I still do not know if it's going to work. Well if I do not like the end result I can face it off.
I went on the computer and wrote the name of the engine in a Word textbox roughly the size of the support. I used Arial as a font and played around with a font size till I got what I needed. I also made sure that all the letters used staight lines. Printed them, cut them and glued them to the aluminium (secondphoto).
Today, after work, went to do some experimenting with a piece of scrap aluminium. I used a 3mm ball nose mill and the groove on the left in the third photo is 0.5mm deep (for the large font size) and the one on the right is 0.25m deep for the smaller font size.
I did the straight vertical lines on one of them (forth photo). I had to take into account the thickness of the paper and glue. So for the large font I went to a depth of 0.6mm and for the other one 0.35mm. Tomorrow I hope to finish the grooving. The plan is to paint the grooves ( I was thinking red ) and then mill the face. At least that's the plan. We'll see if it works out.

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 楼主| 发表于 2014-4-24 05:27:56 | 显示全部楼层
Continued milling the supports with the 3mm ball nose and spent all morning doing both. Removed the paper from the supports and painted the grooves red. I'll give it 24 hours to dry and tomorrow I'll face it off and see what's the end result.

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Faced off both supports and this is the result. Not perfect but passable. I think I can live with it for now. Would I do it again? Don't think so.

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 楼主| 发表于 2014-4-24 05:28:16 | 显示全部楼层
Finished the two supports and fitted to the crankcase. Now it can stand on its two feet.

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 楼主| 发表于 2014-4-24 05:28:38 | 显示全部楼层
Today I spotted the holes for the crankcase bearing. I then inverted the crankcase and skimmed the bottom of the supports so that they will be parallel with the cylinder platform (photo 1). I then put the crankcase on the granite surface plate and with the help of a 10mm silver steel rod I marked the position of the camshaft hole (photos 2, 3 and 4). I also marked the centreline on the cylinder platform.

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