Philip Duclos Fire Eater

[fcheslop]

As a rough check, turn a bit of bar stock down for a similar length and measure it each end .It should show up any problems. Dont use tailstock support
For a boring bar make one as from personal experience I get a better finish than a tipped tool gives
cheers

 

[el gringo]

https://www.google.com/imgres?imgur...ved=0ahUKEwjH7-T01IvbAhWT-lQKHcfUCJ4Q9QEILDAA

 

[CFLBob]

Thanks, El Gringo.

I've seen those before. Not sure if I have anything that can be made to work, but maybe I could get some.

 

[CFLBob]

And... it's ruined.

This has been a busy 10 days. I first finished the cylinder and then put it on the vise, only to find my vise is a bit too small. I could just barely open the jaws enough to grab the thing, then when I tried to close the jaws, it was hitting the cylinder below the centerline, which would push the cylinder vertically out of the vise, or press a notch into it.

I don't know how big a posting I can make, but I'll add images until it tells me I can't.

This is the original test fit. The vise jaws are less than an inch tall, about 7/8 if I recall.

I could pick up a bit more room across the jaws if I could make the jaws thinner. Then it occurred to me that if I made the jaws taller, by about a quarter inch, it would grab above the centerline. I found some lower profile button cap screws than the SHCS that came in the vise, and figured I could thin the jaws by about an eighth inch on both sides, giving me a quarter inch more opening. I had to order the button head screws, but that was just a couple of days delay. Oh, yeah, I ended up leaving the soft jaws 1-1/2" tall. I might lower that a little.

I machined the soft jaws out of some quarter inch aluminum plate I had while waiting for the bolts. Time for a test fit.

Seemed like it was all good. The gap between the bottom of the cylinder and the vise jaw figured to be 1" and I had a piece left over from 1" bar stock. It felt very secure. It took me a while to figure out how deep to cut the fins and the 1-1/2" diameter part of the cylinder over on the right end because it's never really specified on the print. The print does show that the flat should be 1" wide, so a little geometry (and online calculator) showed me I ought to cut it about 3/16" deep - 0.190.

A friend convinced me to put an extra clamp across the top - I guess he was afraid of aluminum jaws replacing 3/8" steel - so I added that. I cut the flat over the base of the cylinder in a few cuts, .025 deep at at time (3/8 end mill) and it went very well. Which led me to decide to take off the 3/32 wide fins in a couple of passes. First pass at 0.100 depth followed by a second pass at 0.190. At the end of the cut, I thought I'd move the end mill toward the base as a spring cut, just to level out any cutting marks. Instead it dug in and ripped the cylinder open. Look at the shelf on the end where I stopped the cut. That's a deep cut at that end.

You can see how bad it is. The Z axis on the mill never went below -0.190", so as I moved right to left along the cylinder cutting the fins off, the cylinder must have pivoted and lifted the right end. I sure couldn't see it happen. You can measure the diameter to the flat by putting the calipers on the fin and the flat at both ends. The end closest to the camera is 1/16" smaller than the end by the pedestal. The flat spot on the cylinder that was supposed to measure 1.000 measures exactly that. Like I say, the entire piece was cut with the EM never going deeper than -.190".

My guess is that the cylinder pivoted because even with the taller jaws and the 1" bar stock spacer, the contact area is still pretty small. There wasn't enough holding force to keep the cylinder from rotating. Maybe really light cuts?

Do you guys think there's a way to fix this? (I don't have any welding ability or tools). If not what do I change to keep from ruining another piece?

 

[el gringo]

And... it's ruined.

This has been a busy 10 days. I first finished the cylinder and then put it on the vise, only to find my vise is a bit too small. I could just barely open the jaws enough to grab the thing, then when I tried to close the jaws, it was hitting the cylinder below the centerline, which would push the cylinder vertically out of the vise, or press a notch into it.

I don't know how big a posting I can make, but I'll add images until it tells me I can't.

This is the original test fit. The vise jaws are less than an inch tall, about 7/8 if I recall.

View attachment 101529

I could pick up a bit more room across the jaws if I could make the jaws thinner. Then it occurred to me that if I made the jaws taller, by about a quarter inch, it would grab above the centerline. I found some lower profile button cap screws than the SHCS that came in the vise, and figured I could thin the jaws by about an eighth inch on both sides, giving me a quarter inch more opening. I had to order the button head screws, but that was just a couple of days delay. Oh, yeah, I ended up leaving the soft jaws 1-1/2" tall. I might lower that a little.

View attachment 101530

I machined the soft jaws out of some quarter inch aluminum plate I had while waiting for the bolts. Time for a test fit.

View attachment 101531

Seemed like it was all good. The gap between the bottom of the cylinder and the vise jaw figured to be 1" and I had a piece left over from 1" bar stock. It felt very secure. It took me a while to figure out how deep to cut the fins and the 1-1/2" diameter part of the cylinder over on the right end because it's never really specified on the print. The print does show that the flat should be 1" wide, so a little geometry (and online calculator) showed me I ought to cut it about 3/16" deep - 0.190.

A friend convinced me to put an extra clamp across the top - I guess he was afraid of aluminum jaws replacing 3/8" steel - so I added that. I cut the flat over the base of the cylinder in a few cuts, .025 deep at at time (3/8 end mill) and it went very well. Which led me to decide to take off the 3/32 wide fins in a couple of passes. First pass at 0.100 depth followed by a second pass at 0.190. At the end of the cut, I thought I'd move the end mill toward the base as a spring cut, just to level out any cutting marks. Instead it dug in and ripped the cylinder open. Look at the shelf on the end where I stopped the cut. That's a deep cut at that end.

View attachment 101532

You can see how bad it is. The Z axis on the mill never went below -0.190", so as I moved right to left along the cylinder cutting the fins off, the cylinder must have pivoted and lifted the right end. I sure couldn't see it happen. You can measure the diameter to the flat by putting the calipers on the fin and the flat at both ends. The end closest to the camera is 1/16" smaller than the end by the pedestal. The flat spot on the cylinder that was supposed to measure 1.000 measures exactly that. Like I say, the entire piece was cut with the EM never going deeper than -.190".

My guess is that the cylinder pivoted because even with the taller jaws and the 1" bar stock spacer, the contact area is still pretty small. There wasn't enough holding force to keep the cylinder from rotating. Maybe really light cuts?

Do you guys think there's a way to fix this? (I don't have any welding ability or tools). If not what do I change to keep from ruining another piece?

 

[el gringo]

If the part was properly held, it wouldn't have moved.

usually the endmill is the one that burrows into the part... make sure it isn't somehow able to move.

Also, why such an aggressive (100 thou) on a tenuous situation?


Ray M

 

[deverett]

Another aid to stop bits moving in the vice is to put a piece of card (cereal packets are good) between the jaw and the work.

Dave
The Emerald Isle

 

[CFLBob]

If the part was properly held, it wouldn't have moved.

usually the endmill is the one that burrows into the part... make sure it isn't somehow able to move.

Also, why such an aggressive (100 thou) on a tenuous situation?

It didn't seem very aggressive. It was a cutting back a fin that's 3/32 wide, so tall in DOC but small in Width. My cutter was 3/8 or 12/32, so I was cutting 1/4 of the cutter width. I only cut one fin at a time.

Of course, I've been giving myself a hard time over that ever since.

 

[CFLBob]

Another aid to stop bits moving in the vice is to put a piece of card (cereal packets are good) between the jaw and the work.

Dave
The Emerald Isle

Thanks for that tip! I have some thin cardboard around but didn't think of that.

 

[CFLBob]

Should I make my soft jaws narrower? Closer to the width of the vise body? That should help the clamping forces out near the left end.

How about shorter? I could take them down from 1-1/2 to somewhat lower.

I noticed this problem while looking at the pictures:

So I started wondering if my mill's head was actually going too far (this is a CNC mill, all driven by keyboard commands or hand controller, so getting it to go between depths repetitively is just the up arrow key - I don't have to type the number every time).

I ruled that out by putting a dial indicator (1" by .001) where the spindle going up and down would compress it. Then raised and lowered the cutter back and forth between -0.100 and -0.200 about 40 times. The indicator never showed a change in position, which means the cutter wasn't getting lower every time I raised and lowered the mill's headstock. I did find my backlash had gotten a little worse, but that would have caused it to end up short of -.190 instead of too deep. So it looks like the only explanation is moving in the vise.

 

[Cogsy]

Are you sure the cutter wasn't pulling itself out of its holder? That would account for the deeper cut and not being able to see the part move.

 

[CFLBob]

Not to be a wise ***, but I'm not sure of anything. At least not much. I think I'm sure that the mill was working properly. When I removed the cutter, it felt as tight as always.

I cut the replacement cylinder over the last couple of days. I should be able to put it in the mill today or tomorrow. I'll spend some time with an indicator and make sure it's level. A friend recommended I cut a shallow pass with an end mill along the soft jaw's face. It could give me two lines of contact on each side instead of just one.

I sketched it in my 3D CAD to get an idea what the slot needs to look like. Something like this:

The o.538 was found by moving the model of the cylinder into the jaw until it got "too close" to the counterbore for the screw. I think if I use a 1/2" EM and cut .032 deep, that's as close as it gets. Make sure the corners are deburred to mar the cylinder less.

 

[CFLBob]

From the "all's well that ends well" category, I didn't post day by day but finished the part yesterday.

And a little different angle look showing the end fins better. Sure needs to be de-burred.

I'm going to do the flywheel next.

Duclos's book goes to the flywheel support bracket next. Mostly I'm doing the flywheel because I'm thinking of putting ball bearings in where he just lets the shaft ride on aluminum (with a little oil). I'll have to design that and order the bearings. I also might remake it as three pieces of sheet, either quarter inch or 3/8" thick , because turning over a cubic inch of aluminum into chips to make the thing like the book's approach doesn't seem right. The bottom would have to be milled for clearance of the rotating flywheel if it's 3/8, but that's not bad. I'd just hold the base and side together with screws on the side.

 

[deverett]

You can use ball bearings from a discarded hard drive. High quality items and Free!

Dave
The Emerald Isle

 

[CFLBob]

Never thought of that. I'll have to see if I have any old drives lying around.

 

[Tim Wescott]

I don't envision this as a build thread, because I have so little to contribute, but I could use some help with questions as I muddle through my build of this engine, from "The Shop Wisdom of Philip Duclos".

I post build threads on model airplane fora (Stunthanger, mostly) so that other forum members can tell me how I'm screwing up. It makes my builds better. Whether that will be welcome here is a question for the group -- I'm new.

... I'll lose more than .001 just turning it in the lathe. I don't know what my 3-jaw chuck's runout is, but .001 is way too good for a 3-jaw ...

You can lose a little less if you're willing to put an indicator on it (or just make test cuts) and shim the short (long?) jaws in a bit. It'll make you wish you had a 4-jaw, but it'll work. You'll still need to go undersize, but the advise you're getting about just making the bore undersize sounds right to me -- there's certainly plenty of commercial engine manufacturers that change displacement by changing bore and little else.

 

[CFLBob]

It'll make you wish you had a 4-jaw, but it'll work.

I have a four jaw, but I still cut the cylinder a bit undersized. It has been long enough that I don't remember exactly what I cut it to. I think it was 0.980. It will give me enough to work with to cut the piston.

I've since seen a video listed on YouTube that shows putting a grinder in a tool post and closing the jaws onto it to make them even and reduce runout. I don't know if that's a good idea. Maybe with something covering the ways to keep abrasive dust from landing on them.

 

[Blogwitch]

Bob,
Don't even think about grinding the jaws in a 3 jaw, I have done it a few times when people didn't believe me, and it soon proved to them that grinding isn't a good solution unless you can throw large amounts of cash and valuale time into it.
Even then, you will be lucky to get an very accurate 3 jaw lathe chuck.
From my own findings, I have found that 4 jaw self centering chucks, straight out of the box (I have four of them at last count) do give better runout figures, plus if you buy a set of soft jaws at the same time, and use them correctly, your precision goes up in leaps and bounds, to zero or very little runout (well under 0.001"),

John

 

[CFLBob]

Making the flywheel on the lathe went as smoothly as expected. It's tedious and requires I change cutters every couple of cuts, but it came out fine. This is halfway cut, but the other side looked just like this.

Once it was cut, it was onto the rotary table on the mill to cut 3/4" diameter holes in it, which I did with a 3/4 EM, the biggest I have. It seems I didn't stop to take any pictures of this, but took a picture when it was finished, next to my first little engine. The big flywheel is 3-3/8 OD with 3/4" holes. The smaller one is 2-1/2" OD with 1/2" holes. Big brother, little brother.

Then it was on to drill and tap for the setscrews. These are at about 10 degrees from vertical, and I had problems with the bits and drill chucks interfering with the flywheel rim. So I had to make two custom tools for this: one to hold a #2 center drill and one to hold the bit to tap the 8-32 threads.

Both were made from 1/4" brass rod. On the drill bit holder, you can see where I tried an 8/32 setscrew. Unfortunately, there was no more than 2 threads in there and as soon as I tried to tighten the setscrew it ripped out the threads. That's when I went to soft soldering the bits in. Back when I was working as an electronics engineer, if someone had showed me solder as ugly as that top one, I would have told them to start over. But this isn't circuitry, and as long as the solder wicked between the brass and the steel, it'll be OK. With those tool holders, I was able to drill, then tap the setscrew holes.

This completed the flywheel and it's ready to use. On to the next part, which is going to be the flywheel bracket. Here I'm going to redesign Duclos' bracket, because I want to add ball bearings into the up rights. I also think that instead of using a block of solid aluminum and milling away 80% of it, I'm going to use quarter inch aluminum plate and hold it together with #8 screws at the bottom.

 

[deverett]

I notice you are using a spotting drill to support the end of the tap handle.
It may be better instead to use a home-made centre from a bit of bar. Just put a length of 3/8" or whatever you have in the lathe chuck, turn the topslide round to 30 deg. and make your centre. Cut off and hold this in the collet or drill chuck on the mill; doesn't need to be hardened. It'll help to save the point of your drill.

Dave
The Emerald Isle