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Old 06-06-2009, 03:03 PM   #101
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Default Re: Open Column Launch Engine from Kit

Quote:
Originally Posted by mklotz
For holes <=0.5", I normally drill 1/64" undersize, then ream.
Thanks Marv...that was the mistake I made. I drilled to the size called for rather than under. Oh well. I'll wait and see if I have problems. Happily I have more material should it be needed.

Countersink...of course. I knew that...forgot that...will probably forget again.

I will edit my post for others.


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Old 06-06-2009, 03:47 PM   #102
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Default Re: Open Column Launch Engine from Kit

The only reason I'm so good at guessing your missteps is that I've made them all myself.

Some other reamer hints:

Run them at about half of drilling speed.

Never turn a reamer backwards in a hole. It will ruin the edges.

Don't run them dry except in brass.


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Old 06-06-2009, 08:30 PM   #103
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Default Re: Open Column Launch Engine from Kit

Thanks for the tips Marv. And I'm happy to know I'm following in your footsteps.

The bearing-port block...



About 0.06 shorter than spec but I'm thinking it'll be okay.

The hole dia is .4375 (7/16 or 28/64) so I used a 27/64 drill bit.
Once again I was happy the TP was nearby.
As I was drilling, the bit grabbed and tried to shoot down into the part and gave up a very shrill whine. Luckily I had firm control on the feed handle. If I'd been a smarter puppy I would have had the z-axis travel stop set so that the bit wouldn't have gone into the vise. As it was...it didn't get that far.

Should I have used cutting oil? Should I have started with a smaller bit and worked up?

Then it came time to ream. That resulted in this thread...

http://www.homemodelenginemachinist....p?topic=5187.0

According to the instructions...I went and drilled and tapped the ports. That produced junk in the bearing hole. What to do? I put the part in the vise and carefully reamed it again. What should I have done?

Loosely attached to the base to see what it looks like...

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Old 06-06-2009, 11:26 PM   #104
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Default Re: Open Column Launch Engine from Kit

Quote:
Originally Posted by zeeprogrammer

As I was drilling, the bit grabbed and tried to shoot down into the part and gave up a very shrill whine.
Dont feel bad, I just did that very same thing. had that piece of bronze all nice and fitted, a tad to rambunctious with the drill bit and sucked that piece of bronze right out of the part. So sad, So sad. Next piece in progress, coffee break now and I'll step the hole size up bit by bit. That stuff is grabby using regular drill bits.

Quote:
According to the instructions...I went and drilled and tapped the ports. That produced junk in the bearing hole. What to do? I put the part in the vise and carefully reamed it again. What should I have done?
Chicken or the egg, running the reamer thru by hand to break off the chips, done that many a time, easy with the reamer and you don't blow out the hole
Quote:
Loosely attached to the base to see what it looks like...
Looking good, can feel your pain with the "Hey the bit wont fit" problem. Spend the time to set it up and something goes haywire. Just part of the adventure. I, not having the experience, just chuckle to myself when the unknown pops up, we learn from it.
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Old 06-07-2009, 12:17 AM   #105
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Default Re: Open Column Launch Engine from Kit

Carl,
A drill ground on the tip like:



can stop the grabbing in brass and bronze. Sometimes just using a hand stone parallel to the length of the drill is enough, especially with small drills. They don't cut as well in steel after this treatment so I have extras set aside just for brass. Just partially locking the feed and clamping the part also works. I sometimes do this on the lathe when I don't want to modify a drill by slightly tightening the ram lock.
Hope this helps.
Dave
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Old 06-07-2009, 01:58 AM   #106
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Default Re: Open Column Launch Engine from Kit

Thanks Foozer. Thanks Dave.

More progress...the rotary valve.

Some of the first advice I got on this forum was to 'sneak up on the part'. There's a lot of good advice on this forum and I suspected this was one and so I did. Turned down to near size (and learning that I can set the dial to zero helped a lot!) then sanding and test fitting...back and forth...back and forth...back and forth...but I got there. Even cooled it down or waited to allow the metal to settle. It fits...but I feel a little binding as I turn the port block. I expect (hope hope hope) that this will clean up after a little bit of running.



The rotary valve. Had some fun parting it off...the lathe stalled, 3 or 4 times, but I got through it. Cleaned it up. Looked good! Then I needed to drill/ream the hole for the set screw. Foo. Busted the tip off the center drill (that's the 2nd time now). Have no idea how to get it out. So I'll pretend it's an oil hole and went to the other side. Center drill (with a bigger center drill), drilled, and tapped. Same problem as before...junk now in the crankshaft hole. Went to the lathe and carefully reamed again. Oh happy day.



A test fit...(well really I just wanted to see what it looks like)...



Now for the sad part to come...and it will come...I still have to cut the two 'watchamacallits' on the valve (two cuts that go part way round the valve). It requires a rotary table and a slitting saw. One boo-boo and it's back to the beginning. (But it will be a little while...I have to get an arbor for the slitting saw and practice a bit before working the valve).

But I am prepared for my propensity to make boo-boos...Have Metal, Will Machine.
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Old 06-07-2009, 02:29 AM   #107
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Default Re: Open Column Launch Engine from Kit

Hi Carl,
The "junk" in the center hole is unavoidable. Just re-ream and you're fine. I'm wondering why you've broken 2 center drills now. The material is carbon steel, right? How fast (RPM) are you going and are you using lube? That shouldn't be happening. Let us know and we'll figure out what you can do to avoid that.
I can't believe that they gave you a piece of matl, the length of which equals the finished lengths of BOTH PIECES. If you were to EDM them apart, they'd still be short! Poor planning on their part!
Now, as far as the whachamacallits, if there is a way you can post a drawing (without giving away any of the plan specifics), maybe we can help

Mark
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Old 06-07-2009, 03:06 AM   #108
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Default Re: Open Column Launch Engine from Kit

Hi Mark,

They are the #1 center drills...kinda small. I didn't use lube (at least on this one) until I got to the 2nd step with the drill bit. And...I may have gone too fast. It probably didn't help I was going into steel. I'm not too bothered about it...I see that this has happened to a couple of other members. More experience will help.

Yeah I was surprised about the length of the piece.

The whachamacallits are two grooves that go around the valve for about 200 degrees and are offset from each other by some angle.

The kit came with decent enough instructions...but they could have been better. Still, with the help of this forum...I'm getting through it.

I'm having loads of fun.

Thanks Mark.

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Old 06-08-2009, 12:01 AM   #109
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Default Re: Open Column Launch Engine from Kit

Carl,
I prefer using a 90 deg spot drill over center drills for most things. The tips on center drills can be kinda fragile as you have seen.
This sounds like a kinda involved engine for one that appears simple. Kudos to you for having a good attitude. That last sentance in your last post says it all, "I'm having loads of fun." Keep having fun!
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Old 06-08-2009, 12:03 AM   #110
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Default Re: Open Column Launch Engine from Kit

I really have the feeling that I'm cheating or developing bad habits. Readers will see what I mean but I must press on...time for the crankshaft.

This is the setup to machine the crankshaft. 0.875" down to 0.218....for 2.31" plus enough change for the live center. Tried to be careful in setting things up. Couldn't find a cutter that seemed to fit. Thought about a thread cutter...ended up with a carbide insert at an angle. Checked everything. Had some interference between the tool post and the live center. Took care of that. Locked down the live center, used a carriage stop, and started cutting lightly (0.003").



Had a little smoke (off the part...I quit smoking a year ago). Periodically used some coolant. I just have a spray bottle that puts out a stream. But things never got too hot. Long springy pieces.

Power feed up to near the stop then fed by hand and pulled back. Went pretty well.
Thought I'd up the feed rate...tried taking 0.01. Oops. Got more substantial strands of a goldish color. Quickly had a mass of stuff twirling around. This is what it looked like. The smoother looking strands are the 0.01 cuts...the springy looking ones are 0.003 or 0.004.



Backed off to 0.005 at a time and cleaned out the strands every once in a while. Needed to go from .875 down to .218 for .657. That would require some 65 passes. Took some time but I got there. See the dark spot behind the lathe? My tables are topped with hardboard. They're like a sponge. I don't really mind...they look cool as they are used (and they're replaceable). (In the back is a piece of plexi to keep the stuff that's thrown off the lathe off the wall.)



After much sanding...and trial fitting...the pillow block and rotary valve slip on. A lot of sanding. (I protected the ways with a paper towel when I sanded.) Prior to sanding the crankshaft had a slight taper of less than a couple thou from tail stock to head stock. I'll have to do something about that before I cut another long piece.



Flipped the part around. Had to remove some 1/2 inch or more. That would be a lot of facing. Hacksawed a big chunk then faced and sanded. The OD of the crankshaft didn't need turning down - just sanded it to brighten it.



Now just to see what it looks like so far...



Not finished with the crankshaft yet...needs a flat for the setscrew to hold the rotary valve and a flat, at an angle, for the flywheel. Also need a hole to attach the piston rod.

Pretty happy. Time to relax.


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