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  #11  
Old 05-25-2017, 01:00 PM
KAD KAD is offline
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[QUOTE=Marc Bourget;136968]
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If you use a steel connecting rod and a needle bearing like a two stroke engine does then a couple of drops of oil is all that's needed and it'll take a huge amount of impact and not fail.

Kirk,

I believe that approach requires experience to get the respective materials and heat treat correct.
Your correct if it's going to be turning at 10,000 rpm but at our 1725 it's just an idle speed for it. Oil Harden steel and draw it out is going to last as long as we do ....I suspect.
That's just my opinion I haven't built one so I'm not saying It's fact.
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  #12  
Old 05-25-2017, 01:44 PM
bobadame bobadame is offline
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[QUOTE=Marc Bourget;136968]
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Originally Posted by KAD View Post
If you use a steel connecting rod and a needle bearing like a two stroke engine does then a couple of drops of oil is all that's needed and it'll take a huge amount of impact and not fail.

Kirk,

I believe that approach requires experience to get the respective materials and heat treat correct.
Hardened races and rollers are available. No heat treating necessary.
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  #13  
Old 05-25-2017, 01:57 PM
Bob Bob is offline
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Michael,

I guess I don't have any build pics, just a few of the different dies I made for it. Here's a pic of machine #1 in a bit bigger image size and one of it in a test fit of the pieces. It's just a bolt together machine. The mechanism is running in bushings at every point. I do have some needle bearings for the ram guide to try out though if I build another. The drive shaft isn't hardened on either machine, that being made from stress proof steel. Like Bob mentioned above, there are some needle bearings available that include a hardened outside race for press fitting onto a softer shaft, so I'm going to try them out. Then change the rear bushing to a ball bearing.

I loved the machine Ben built and thought of making a copy of it for this trial of my quick change dies. But in the end decided to roll my own. I learn more that way. I liked the way he used a bearing in the yoke, mine was based on the Trace-A-Punch completely. Someday I might try a bearing there as it would remove one lube point. The stroke length of 1/8" came from my old walking beam machine's last setting.

Originally I came up with 1/4" steel being "good enough" with some give to it for the sides. But I didn't have enough to try it out. Decided 5/16" a better choice, but again, didn't have any. Had the 3/8" in 12" wide pieces, so that's what drove things. And it has been way more than adequate, so became my base for experimenting. For machine #2, I had alignment problems between the upper and lower dies. I had the aluminum on hand, but I had already made the stand. That's why I pocketed out the areas on the inside, to keep the outside the same as with the steel sides. Yep, I'm cheap like that!

I have run both different side plates in Catia fea, but i had no idea of the force needed to shrink steel or the force the mechanism generates. What I did was just apply a force in the fea to the steel sides, then the same force to the aluminum and changed the aluminum thickness to match the results I got from the steel analysis. And I had to learn fea on the fly as that was never part of my old day job. Backyard engineering. All that math hurts my head anymore. The results have pretty much proved things out on the real machines, I really can't tell one from the other in use outside of better die alignment. Weight wise, they're within a pound or two of each other with the first having a smaller lighter motor.

I've done the same thing with the new longer aluminum sides in fea. As I raised the force to double, I can see the sides start to flex horizontally in the model. But in matching the steel numbers, they do fine as designed. Not 100% sure right now, but I think the new sides result in a 15" throat, the original two machines are 8". Plenty deep enough for a lot of work to be done in. I'd like to cast the new sides from 713 alloy aluminum at some point. I won't even attempt another build until I reach that point. Cast the ram guide too along with the pulleys. I already do cast the pulleys. The flex I see in fea does worry me though, as I said I got no idea of real world force. And that may lead to just machining the sides. That concern is why a stand change will happen, to try to make the stand a structural part of the machine. I'd love to just wheel a machine around the shop instead of picking it up and carrying it, even though it is handy at times to be able to do that.

Mini Shaper No 1 In Process.jpg

Mini Shaper No 1.jpg

Steve, thanks for fixing the image. What happened to the insert image function, it now request a url?
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  #14  
Old 05-25-2017, 02:34 PM
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Kerry Pinkerton Kerry Pinkerton is offline
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Still there Bob. Click on the paperclip and select insert all or insert the photos one at a time.
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  #15  
Old 05-25-2017, 02:57 PM
Michael Moore Michael Moore is offline
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Thanks for the extra photos and details! And Kerry, thanks for doing the thread split and Steve for moving the images inline.

I'm plenty familiar with conrods after 40+ years of racing motorcycles. The Scotch yoke seems like it could be both more compact and more robust in that smaller space compared to the amount of space taken up by a crank/rod mechanism.

It might benefit from rotating the drive 90 degrees so the out of balance movements are in-plane with the chassis. Or perhaps a second SY block/eccentric with 180 degree phasing could be mounted behind the working part of the mechanism just to add some counterbalance, though that would introduce a short rocking couple.

If the drive is rotated the motor could go above the SY on top of the chassis (as was done on some ShopDog machines) and the long drive shaft might then be shortened significantly as it wouldn't have to go to the back of the machine past the throat opening.

cheers,
Michael

Last edited by Michael Moore; 05-25-2017 at 03:06 PM.
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  #16  
Old 05-25-2017, 03:55 PM
Ken Hosford Ken Hosford is offline
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I have savage ? nibbler it runs the scotch yoke . It makes some noise don't most nibbler It will do 3/16" steel
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  #17  
Old 05-25-2017, 04:00 PM
Bob Bob is offline
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Thanks Kerry for fixing them. Now that you mention it, that's how I did it in the past. Life's short, but my memory is shorter.

Quote:
Originally Posted by Michael Moore View Post
It might benefit from rotating the drive 90 degrees so the out of balance movements are in-plane with the chassis. Or perhaps a second SY block/eccentric with 180 degree phasing could be mounted behind the working part of the mechanism just to add some counterbalance, though that would introduce a short rocking couple.

If the drive is rotated the motor could go above the SY on top of the chassis (as was done on some ShopDog machines) and the long drive shaft might then be shortened significantly as it wouldn't have to go to the back of the machine past the throat opening.

cheers,
Michael
Michael,

Those are some good thoughts. I have a picture of a small machine that I started trying to emulate, but gave up. I believe it's a scotch yoke too. One thing I really like about it is it looks like the ram is moved by rotating the motor up or down allowing the die to be positioned while the machine is running. That was one thing I loved about my walking beam machine. Sadly the new machines don't have anything to do that. And that would be one thing I would go to some extremes to add.

The motor ended up below as I felt the machine would be top heavy with it above. And I tried, but couldn't see a simple way to mount it to the side and drive the ram direct from the motor shaft. I bought a C-Face motor in case I figured it out though. A heftier machine would help there, these are just too light in weight at 100 lbs. So the drive shaft entered the picture. The original machine intend was to just test the die mounting I had come up with. So many compromises were made to the basic machine along the way to testing the die mounting. It was a quick build after I got along on the die holding portion.


Here's the machine I mentioned above. I've never found much info on it over the years. Looks like I found it in 2011. Hey, that inserting thing worked. Thanks again Kerry.

Pullmax P-1.jpg
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  #18  
Old 05-25-2017, 04:28 PM
Michael Moore Michael Moore is offline
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That photo is labeled Pullmax P-1 but it looks a lot different from the P-1 shown in Vol #3 of Tim Barton's books and I don't see a similar machine there.

Here's one like it (actually I think it is the same machine after restoration). I can't make out the model number when zoomed in but in the post they are from it refers to it as a P-1 (B):




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  #19  
Old 05-25-2017, 05:04 PM
Bob Bob is offline
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P1 is what I had it labeled as too. I had not seen that spruced up version of it, nice. There has to be more of those, funny there's only the one in picture form. Home made dies on it as well. I really do like that machine but clearly it's not the do all machines most other pullmax's are. I got no room for a large pullmax, so I aim lower.

If I had the ability to cast cast iron, maybe I could create one. Or possible do a weldment. What I like about it too is it's an oil bath. That solves the issue of having to oil things on a routine basis, one of the things I don't like about my little machines. Not been a problem so far though.

So here's a question on the drive for these. If a bearing is used, it'll be harder than the ram. At least in my case. I can't grind to finish parts, got no grinder. So I have to work things in a annealed or semi hard state. Bearing races are hard and I doubt I'd get a ram built that was harder. So I went with bronze 954 bearing material and it's holding up ok. But I don't have a ton of hours on them either. Would a ball bearing be a wise choice there?

My old Trace-A-Punch was a bit noisy due to some slop in the scotch yoke. I replaced the shoe in it, but I measured the ram slot to be oversize. So even after the new shoe, it was noisy. Mine aren't noisy at all right now and I'd like to keep them that way. Would a bearing fair better there?
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  #20  
Old 05-25-2017, 07:55 PM
Michael Moore Michael Moore is offline
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Bob, you don't need to be able to cast iron, you just need to be able to make a pattern and find a foundry interested in working with you. These machines look like a pretty big pour for a backyard foundry project even in aluminum.

You'll need some minimal amount of play in the Scotch yoke. I don't know how hot they get and how much expansion will take place, and whether it makes things looser or tighter. Noise should be at BDC and TDC as the thrust faces swap. A thicker oil or grease could act as a cushion to reduce the noise.

I think many of the bearing bronzes will work harden some in use. If they run on a nice surface with some lube they should last for a very long time as long as their PSI load from the work is within the ballpark. 660 or better instead of oil-lite is probably a good idea as long as it gets enough lubrication.

Instead of worrying about hardening and grinding the parts why not instead buy a piece of hardened and ground flat stock and attach it to the ram? You might only need that on the lower side that sees the working pressure. If you have sliding then you want dissimilar materials/hardness between the two parts.

The Frelon Gold linear shafting bearings are self-lubricating, quiet, tolerant of environmental contaminants and can carry a lot of load. Thomson Quick Shaft is case-hardened and ground, and those parts have interested me for some time for DIY machinery. There is a SFM limit on the bearings that you'd have to calculate but that is lower when the bearing is oscillating than when it turns in a constant direction so it may give plenty of RPM. But a sealed crowded or caged needle bearing between the block and eccentric would give a lot of load capacity too.

You could have a rolling element bearing between the block and shaft, and then make the block from bronze (or steel with bronze faces which could even be done with hardfacing and milling) and then the bronze runs on the steel ram.
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