设为首页收藏本站

科技网

发动机建造 Kiwi Mk2(绝对精华)

[复制链接]
 楼主| 发表于 2014-4-25 08:55:08 | 显示全部楼层
The cast iron you got in the kit is quite likely a piece of continuous-cast normalized and annealed cast iron barstock. That stuff almost guaranteed to have better machining qualities than the c.i. that Westbury had to deal with 75 years ago or whatever it was. It shouldn't have any internal stresses or hard skin to speak of.You may want to consider making "small pattern" nuts. I don't know if the metric system has an equivalent, but here in the U.S. there are "large pattern" and "small pattern" nuts. You'll need to translate this concept into metric if you decide to pay attention to it, but that shouldn't be difficult.Large pattern nuts are the type commonly available for machine screws, so if you scale a 1" diameter bolt down to 1/8" (0.125") diameter (which happens to be #5 machine screw), the commonly available nuts for #5 machine screws won't be correctly scaled to correspond. The nuts you typically buy for #5 machine screws are large pattern and 5/16" (0.3125") across the flats. A standard nut for a 1" diameter bolt, however, is "small pattern" and is 1.5" a/f. Scale that down to 1/8 and the scale nut should be small pattern and only 3/16" (0.1875") a/f. Of course you could be modeling a "heavy pattern" nut for a 1" bolt, which is 1 5/8" (1.625" a/f), in which case a 1/8 scale nut wold be 13/64" (0.203125") a.f....When I made the bolts and nuts for Kiwi, I guessed that Kiwi was about 1/4" scale of a comparable prototype, so with the aid of Machinery's Handbook and some guesses I figured out the scale bolt and nut head sizes for Kiwi's bolts and nuts and made them based on that.As a side issue, if the 1" diameter bolt one is scaling down is 8 threads per inch, at 1/8 scale the bolt ought to be 64 tpi, and a #5 machine screw is only 40 tpi. The thread pitch, however, is not anywhere near as noticeable as the nut proportions when making it look "right." Using fine instead of coarse threads helps.
 楼主| 发表于 2014-4-25 08:56:12 | 显示全部楼层
Nothing to do today, so I invented something to do for the Kiwi. The flywheel on the engine uses a split tapered collet to hold it in place. So today I did a trial run of doing this tapered collet and it's mating hole. Used some left over BMS and drilled and reamed to the appropriate dimension. In photo 1, the one on the left is representing the hole in the flywheel, whilst the one on the right will eventually be the collet.
Started first with the imaginary flywheel hole. Set the topslide to 5 deg and using my smallest boring tool, turned the taper (photo 2). Next, I did the taper on the collet (photo 3), using exactly the same topslide setting and same tool. Obviously, I had to change the direction of turning of the chuck with this setup. As usual in my boring operations, the surface finish is not something to write home about.
Parted off the collet, used a hacksaw to create the split and the two finished products (photo 4).

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

 楼主| 发表于 2014-4-25 08:56:41 | 显示全部楼层
And the two parts lightly mated together (photo 2). When the flywheel is bolted on, it should draw the split collet into the flywheel hole until it becomes flush in the hole. Photo 1 is depicting the same two parts on the crankshaft. This setup is also showing me to where I need to take the crankshaft thread next time.
At least now when I actually do the flywheel and collet I know exactly how to do it.

发动机建造

发动机建造

发动机建造

发动机建造

 楼主| 发表于 2014-4-25 08:57:44 | 显示全部楼层
Today I was thinking of making the special nut for the other side of the crankshaft which holds the pinion in place. Should be an easy job but then I remembered that I don't have an 8mm fine tap set. So that's that. The nut is not going to happen in the next two days. Then for no particular reason I took the timing gears out to look at them. I decided to measure the thickness of the pinion, which goes on the crankshaft, and horror of horrors, it's too thin. Measured again and it's too thin. Measured the spur wheel and it's too thick!!
I have a suspicion that the thicknesses of the gears were by mistake interchanged when they were made. I guess I can thin out the spur wheel but I can't do anything about the pinion (actually there could be something done but I am going to leave that as a last resort).
So I need to email Kirk at Hemingways and see what he says, but I guess I'll do that when I come back from Paris. These gears have been giving me problems from day one. First they were out of stock and now they are of the wrong size.
Finally back home from abroad. Really missed my Kiwi. Whilst away managed to get in contact with Kirk at Hemingway and he agreed with me that the pinion was undersize and he would be sending me another one. I hope that he measures it before sending it.

This morning I went to buy an 8mm fine tap set for the special nut of the crankshaft. Arrived at this shop, asked for the taps and the guy asked me which one!!
"What do you mean?" I said. Well it seems that there are two pitch sizes for 8mm fine, 8 x 1mm or 8 x 0.75mm.
Obviously I did not know which pitch size I used for the thread so had to return home empty handed.
Back home I checked and I used the 8 x 1mm die to make the thread. Hopefully I will get the taps next Monday.
 楼主| 发表于 2014-4-25 09:00:18 | 显示全部楼层
Finally today I managed to do something on the Kiwi. Started work on the flywheel. I won't be following Westbury's instructions on making the flywheel so we will see how it goes. Used the bar stock that came with the kit, chucked it in the lathe, and faced one side. Then I drilled a shallow hole and opened up progressively with slot drills to 15mm and a depth of 11mm. Using a boring bar continued to open up the hole to 1.5" and a depth of 11.1mm. This should be the rear side of the flywheel.

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

 楼主| 发表于 2014-4-25 09:01:12 | 显示全部楼层
Continued work on the flywheel. Cleaned up the rear end of the flywheel (photo 1). I was then going to start the front end of the flywheel but then realised that I have never cut a V-groove for the pulley.
After a bit of head scratching I decided that a lathe tool had to be ground from HSS. Marked the angles on a 3/8" HSS bar I had (photo 2). Sorry but the photo is a bit out of focus. After a lot of grinding the tool was finished (photo 3).
I gave it a try on a piece of mild steel. I kept the tool a bit below centre line in the hope of avoiding a dig in. The trial run was satisfactory (photo 4).
I am still not sure if this is the correct/easyest way of cutting a V-groove, so if there is a better way please chime in.

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

 楼主| 发表于 2014-4-26 08:43:35 | 显示全部楼层
Continued work on the flywheel. The sequence of operations on the flywheel changed a bit from yesterday. So today I chucked up the flywheel and rough machined the front and also the diameter. Left all dimensions about 1mm larger (photo 1).
I then turned a piece of 10mm silver steel to 8mm and threaded the end 8mm fine (photo 2). This is going to be a mandrel on which to hold the flywheel for further machining.
I then chucked the flywheel again with the rear facing out and checked if it was running true (photo 3). Satisfied that it was running true, I drilled a 10mm hole and machined the taper (photo 4).
Left the taper setup as is so that tomorrow I will machine the tapered collet with the same setup.
p.s. This morning I also managed to buy the 8 x 1 mm tap set.

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

 楼主| 发表于 2014-4-26 08:44:33 | 显示全部楼层
Machined the tapered collet from a piece of 15mm BMS using yesterday's setup. I then drilled and reamed the hole 8mm. I took it out of the chuck and then I thought, "Why not do another one at the other end, just in case". Problem was that I had not faced the other side and I could not disturb the lathe setup, so I milled the face of the bar.
Did the taper and 8mm hole on the other side of the bar (photo 1).
Parted off one of the collets, and hacksawed the slot. I was too lazy to setup the slitting saw in the mill. So I marked the centreline of the collet, clamped it in the milling vice just above the centreline and started the slot with a hacksaw blade supported on the vice jaws (photo 2). I then turned it 90 deg and used the hacksaw to continue cutting the slot. Deburred the collet and gave it a try on the mandrel I had previously made (photos 3 and 4). I really clamps the flywheel nicely.
Only problem I can anticipate, is that if I had to remove the flywheel from the actual engine, most probably I would need a puller.
Tommorrow going for a couple of days to Munich so I guess I will do the other collet after I come back.
p.s. I hope I am not overdoing it with the build photos. If the moderator thinks I should reduce the number of photos, I will oblige.

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

 楼主| 发表于 2014-4-26 08:45:01 | 显示全部楼层
Finally back home. This morning finished off the second spare tapered collet for the fly wheel. I chose this tapered collet to clamp the flywheel to the mandrel I have already made.
Used an ER32 collet holder instead of the three jaw chuck and a live centre to machine the front part and the diameter of the flywheel. Kept the diameter of the flywheel about 1mm wider than the plans to give slightly more mass.
Then I machined the pulley groove with the tool I had already made. Made sure that the tool was at exactly 90 deg to the flywheel by using a DTI (photo 2). I machined the groove very, very slowly and thankfully the material used for the flywheel (from the kit) had good cutting qualities.
Next operation on the flywheel is to clean up and polish it. Not looking forward to do that, but I have to do that next otherwise it will never be done.

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

发动机建造

 楼主| 发表于 2014-4-26 08:45:20 | 显示全部楼层
This evening, finished the flywheel and could not resist the temptation to give it a trial fit to see how it looks. I did not lock it with the nut just in case I could not remove it.

发动机建造

发动机建造

发动机建造

发动机建造

您需要登录后才可以回帖 登录 | 注册

本版积分规则

辽公网安备 21100402204006号|科技网 ( 辽ICP备07501385号-1   

GMT+8, 2019-11-21 14:59

Powered by tech-domain X3.4 Licensed

© 2001-2017 Comsenz Inc.

快速回复 返回顶部 返回列表