Author Topic: 31/2" Tich  (Read 1976 times)

Offline samc88

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Re: 31/2" Tich
« Reply #30 on: July 13, 2020, 04:13:04 PM »
I drilled the crank pins, typically I havent got a reamer so I've ordered one. I simply moved the mandrel to the drill vice and clamped everything down. This has resulted in holes in the same place in each wheel.

Since the 4 jaw is in the lathe I think I'll look at turning the eccentrics next (I'm edging towards doing the walschaerts valve gear but may make the slip eccentrics since I have enough material for practice)

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Offline samc88

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Re: 31/2" Tich
« Reply #31 on: July 13, 2020, 09:33:53 PM »
Cracking on with the running gear and got the pump eccentric machined other than cutting and facing to length tomorrow evening and running my reamer through it

The groove was cut with a stumpy grooving tool I have which works well in the mini lathe as it has no extra length to flex. I then marked out the axle centreline and used my wobbler to set the centre. First time using it (I usually use 2 dead centres and the dti) and it works well.

Really satisfying job



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Offline samc88

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Re: 31/2" Tich
« Reply #32 on: July 14, 2020, 05:09:11 PM »
My 5/16" reamer came in the post today so did the wheel centres nd pressed one on each axle. Before this I took a fraction off the other end, my pan is to use loctite on the other end so I can get the quartering right. Being my first loco I didn't trust myself with pressing on both ends and keeping everything aligned, I should have leway with the loctite to get everything spot on whilst it's setting

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Offline samc88

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Re: 31/2" Tich
« Reply #33 on: July 15, 2020, 07:41:34 PM »
Finished the eccentric. Drilled and tapped for a 6BA grub screw, then used the rotary parting tool to cut to size before facing off to length and reaming to 3/8. Fits nicely on the axle, just need to get a grub screw for it

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Offline samc88

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Re: 31/2" Tich
« Reply #34 on: July 25, 2020, 02:13:56 PM »
Had my first go at making an eccentric strap yesterday. Looked complex at first but the way LBSC describes doing it is actually fairly straight forward. The only difference I did was to size the hole to the job (I rechecked the eccentric in the 4 jaw to have the groove running true, bolted the strap to it and tightened it until it started binding up, then using a feeler gauge in the open gap between the halves told me how much to take out of the eccentric, turned out to be 8thou to get a nice running fit).
 Pretty enjoyable thing to machine and really satisfying seeing it work when I test fitted to the axle. I'll mill the groove for the pump rod to be fitted later on as it means setting the vertical slide up and I'd rather do that when I have a couple of milling jobs to do to save set up time

My new Er32 collet chuck came in the post this week so might look at making the crank pins next to try it out. I also think it'll work better for lathe milling as it's more rigid than the other collet holder I have

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Offline cnr6400

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Re: 31/2" Tich
« Reply #35 on: July 25, 2020, 05:18:45 PM »
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn: lookin good!

Offline samc88

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Re: 31/2" Tich
« Reply #36 on: July 26, 2020, 08:07:57 PM »
Thanks cnr, I'm really enjoying this smaller side of engineering, quite a nice change from my normal job dealing with big stuff in boats.

Made a start on crank pins. First thing I did was to make the washers, I chucked up a piece of 3/8" mild steel, faced, centre drilled and drilled with a No. 41 drill then countersunk. Parted off to a thickness of 1/16" which went well.

Once that was done I started on the driving crank pin made from 1/4" silver steel (drill rod I think it's called over in the US). To start with I faced and turned down the spigot to fit in the wheel to the dimensions on the drawing, this led to the wheel being a slip fit on it, not ideal. Then i remembered I had some really small bore gauges and using them in the crank pin hole in the wheel I found my reamer cut the hole oversize. Not to worry. I started again and got a much better fit (1.5 thou over hole size so is a nice fit). The wheel is just starting to go on the end so should press together quite well I hope. Will part off and do the other one tomorrow.

I have some 3/16" silver steel in the post too to do the other pins.

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Offline samc88

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Re: 31/2" Tich
« Reply #37 on: July 28, 2020, 08:55:43 PM »
Not really done much a I've been sorting out my camping equipment for going away in the land rover this weekend. I did find time to finish off the first driving crank pin. Achieved a very nice light press fit in the end and went together well in the vice

I'll probably look at making the rest next week once I'm back, or I'll make a start tomorrow if I get time

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