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发动机建造 Kiwi Mk2(绝对精华)

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 楼主| 发表于 2014-4-22 04:36:26 | 显示全部楼层
First part finished.
Maybe tommorrow I will polish it with a Dremel (at least the visible outside part). This week I do not think I will be doing anything else on the Kiwi as I have a day course (hate it) and then I am off to Munich (Germany) for some sim sessions (love it).

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 楼主| 发表于 2014-4-22 04:37:15 | 显示全部楼层
So here am I in Munich in the hotel room pouring over the Kiwi plans. Its too cold outside (at least for me) to go running around the city.Having finished the tappet guide, my next item in the build is going to be the tappets, and I noticed a mistake (I was warned to watch out for these). Actually it's not a mistake but a difference between the diagram of the tappet on the 1960 magazine article and the diagram on the large plans. On the magazine, the bottom of the tappet, the cam follower (is this the correct terminology??) is drawn as semicircular (having the same radius as the tappet guide), whilst on the plans, the same part is rectangular. I suspect that on the article it was semicircular more for aesthetic than practical reasons. At the moment I am leaning more on doing the rectangular version for obvious reasons.
I was looking at the recess on the tappet where the pushrod fits and also the same recess on the rocker arm where the other side of the pushrod fits. They are both 3/32" and 1/8" deep but have a slight taper so that the pushrod does not bind at its maximum angularity.
Finally back home where the temperature is more decent (18C). Whilst I was abroad I kept thinking about the above post (tapered holes for the pushrods) and finally came to the the conclusion that I need to trywhat happens if I use a slightly wider untapered hole (3mm ball nose mill). So tommorrow I intend to experiment on a scrap piece of steel and see what happens.Also tommorrow I need to figure out, with the plans in front of me, the intended use of all the pieces of bar stock that came with the castings.


Today I drilled a 3mm hole in brass to the specified depth of 1/8" using a ball nose and tried the pushrod to see at what angle it touches the side of the hole. For sure the tappet will not be at this angle and I do not think the rocker will also need this angle. So unless I think of a better way I will use this method instead of the tapered hole.

发动机建造

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 楼主| 发表于 2014-4-22 04:38:05 | 显示全部楼层
Today I tried solving the jigsaw puzzle of the bar stock that came with the kit. I tried to match the pieces of raw material to parts of the engine. I was never good at jigsaw puzzles and did not match everything. At least the pieces of silver steel and bronze which are hard to source locally I managed to match.I also sourced from my stock the pieces of BMS I will be using for the tappets and rocker arms. Did not do any machining today as the lathe was doing a funny noise which was due to a spindle belt soaked in oil. Could not change it today as it's a holiday.Spent the rest of the day mostly looking at my youngest daughter playing Assasin's Creed online.

OK. Today I changed the belt for the lathe and this evening started work on the two tappets. Started with a 12mm round section BMS and faced it. I then centre drilled the face and drilled the tappet hole with a 3mm ball nose end mill. I then reduced the 12mm section to 5mm. During the final cuts all the time checking with the tappet guide. Brought it down to a slip fit with 280 and 400 grit sandpaper. I then parted off the piece. I did not part it off right through but hacksawed the last part.
Next operation will be on the mill with a dividing head to give the cam follower the rectangular section as per plans.

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 楼主| 发表于 2014-4-22 04:38:29 | 显示全部楼层
This morning I continued work on the tappets. The original plan was to put it in a dividing head on the mill and face the cam follower and give the rectangular shape in one setup. But that means I have to true up the dividing head on the mill table and I hate doing that. So, new plan. Put the milling vice on the table and faced both tappets. Then removed the vice and put the dividing head on the mill table and gave the tappet heads their rectangular shape without needing to true up neither the vice or dividing head.

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 楼主| 发表于 2014-4-22 04:38:54 | 显示全部楼层
I then cleaned up the tappets and hand fitted the tappets in the tappet guide.

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 楼主| 发表于 2014-4-22 04:39:48 | 显示全部楼层
This evening decided to start work on the rocker arms. Using a lenght of 10mm x 10mm BMS to cater for both rocker arms. Started milling the bar to dimension. Finished three sides only. Tommorrow will continue on the fourth side and hacksaw it in the middle.

I see now that I am an advanced member. Must be something to do with the number of posts. I also see that somebody gave me a karma point. For what I don't know. Whoever it was thanks.
Today I continued milling the fourth side. I then marked the lenghts of the rockers and hacksawed the excess. Filled the parts a little closer to the line and then milled off the sides. Ended with two pieces of BMS for the rockers ready for further machining.

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 楼主| 发表于 2014-4-22 04:41:05 | 显示全部楼层
Shucks guys, another two karmas. Thanks to the karma givers but I haven't done anything special up till now. Guess I am doing something right.
This evening continued on the rocker arms. First I drilled the oil hole for the shaft by using a 1.6mm centre drill. That means I drilled the holes and coutersunk them in one operation. Next I drilled the 3mm holes for the pushrods using a 3mm ball nosed mill. As these holes are off the centreline it will help me keep track of which is the front and back of the rocker arm.
Spent nearly 2 hours on these 4 holes. Good thing I am not on a production line!

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 楼主| 发表于 2014-4-22 04:45:35 | 显示全部楼层
This morning continued work on the rocker arms. At first I was thinking of drilling the 6mm hole for the shaft that goes through the rockers but then I thought that when clamping the rockers for further work I might bend or squash the hole. So no holes for now and decidedm to start reducing the side faces as per plans. The plans also show the cuts to end with a radius but no radius dimensions a given. Using a radius gauge I estimated that 1.5mm radius should be close enough. I could have opted to do with without a radius but decided that as this part was visible, a radius cut would be nicer.
At first I thought I would use the faceplate and use a profile tool that I have but when I checked the tool it had a diameter of 6mm. Too large. Faceplate method went out of the window. My other option was the rotary table and use a 3mm ball nose mill. Out came the rotary table and it was located on the table. New problem. How am I going to clamp that small piece of steel to the rotary table. After a bit of head scratching I remembered I have a small 25mm pin vice. Would this work? There only one way of knowing and that is by trying it out.
Marked the centre of where the hole should be and clamped it in the pin vice. Put the vice on the table, located the crosshair (a bit fiddly) and clamped the vice on the rotary table. Reset the DRO x and y to zero so that I do not need to locate the rotary table again and with a scriber in the collet marked the sides of the cuts by displacing the y axis the required amount.

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 楼主| 发表于 2014-4-22 04:46:06 | 显示全部楼层
Started the outer cut and brought it down to required depth using light cuts (0.1mm). The plan was that then I would do the inner cut and then clean up the middle with an end mill. But as usual this plan changed. When I finished the outer cut I started going inwards slowly in 0.1mm increments using the same 3mm ball nose cutter. Don't ask because I can't remember how many times I turned that hand wheel. Eventually I finished. Three sides still to go. Maybe this evening I will do the opposite side. The cut has to be twice as deep as the centreline is offset.

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 楼主| 发表于 2014-4-22 04:46:34 | 显示全部楼层
This evening I did the other side and now I can't feel my arm. Maybe tommorrow I will start on the other rocker arm but I doubt that I will do both sides.

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