[SCzEngrgGroup]

Looks good! I need some of that track for my machine...

It's usually called "drag chain", and is available in many sizes on E-Bay for next to nothing.

Regards,
Ray L.

[tbev]

Foot petals coming in today, I'm stoaked! I was looking for a nice foot petal, but noisy of them are cheap pos's and most need to be wired up , just lid of things I didn't like about a bunch of different ones...I finally found a great company, they are supposed to be the best, the petal is really nice and it will be all wired up ready to go. I'll post pics and I'll shoot a YouTube video of the whole thing tonight.

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[tbev]

Here's the complete video:

https://youtu.be/AxnHQgmhqeY

[tbev]

Happy Thanksgiving Everyone! I hope your spending done time out of the shop with your families. Parts will be landing this upcoming week, as soon as they are all in I will have your PDB's in the mail. I'll let everyone know when they have shipped and send tracking info.



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[brianbonedoc]

I love the function but I wonder how much force this single stage air cylinder applies

[tbev]

I love the function but I wonder how much force this single stage air cylinder applies

It's enough, quite a bit overkill actually. When I started figuring this out my minimum requirement was that it would compress the washers from the stock Tormach 1100 PDB, the washers I'm using hold more than the ones the 1100 does.

[brianbonedoc]

Good to know! How many bellevilles and what rating are they?


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[tbev]

This is the 1100, I'm pretty hard on it, and pull out isn't something I could tolerate. The Belleville washers being used in this video are not as strong as the ones I will be including with the kit. I just left the shop, I'm not sure about the rating but they are a significant amount more than these. This is aluminum, 3fl Tormach CrN Coated EM cutting at 5000 RPM, 0.1WOC, 0.4DOC, @70 IPM. . That's my standard production recipe for that half in cutter, it runs 36 hours at a time, no pull out.




https://youtu.be/NzLOQUK3FmA

[brianbonedoc]

Beautiful work tbev!

[SCzEngrgGroup]

It's enough, quite a bit overkill actually. When I started figuring this out my minimum requirement was that it would compress the washers from the stock Tormach 1100 PDB, the washers I'm using hold more than the ones the 1100 does.

I'm really struggling with the math here, simple though it is.... That appears to be a 3" air cylinder, which means a single piston will provide only about 700 pounds force at 100 PSI. Even if it's a triple-stage cylinder (and it does not appear long enough to be triple-stage), that's still only 2100 pounds maximum force. Actual drawbar tension when holding the tool will be considerably lower than that, as maximum force is required when releasing the tool. The Tormach PDB provides ~2500# maximum drawbar tension, and still often suffers from pull-out, per some reports here. So, how can you possibly be providing higher drawbar tension than the Tormach with such a small cylinder?

Regards,
Ray L.

[nitewatchman]

I'm really struggling with the math here, simple though it is....

I was having the same thoughts. The static calculations do not smell right.

The PDB on my 1100 works okay most of the time. It is kept well lube with Nuclear Grade (long story from my sorted past) Pure Nickel Never-Seize and adjusted very tightly. The opened drawbar will just allow the TTS holder slide in and out with drag at the expense of an occasional pair of Nylon Bolts on an ATC Finger (McMaster-Carr in a bag of 100). PDB is operating at 115PSI.

The pullout only seems to occur when the machine is pulling near max horsepower on the load meter and encounters some squeal or chatter. I believe that the holder must first slip in rotation breaking the static friction lock holding it in place. Once this slip occurs, especially in the presence of vibration, the holder just screws out of the collet. This increases tool overhang and breaks contact with the TTS flange worsening the chatter and increasing the slip. I do not believe that the lateral force along exerted by the helical angle of the cutter is sufficient to pull a tight holder out of the collet, not at the power levels available on the 1100.

Is it possible that the single cylinder, with it much lower force than the triple 1100 cylinder, works simply because the lower powered 440 does not have sufficient power the slip the TTS holder in the collet?

Gary

[SCzEngrgGroup]

The 440 spindle is lower power than the 1100 - 3/4HP vs 1.5 HP. And the cut he describes on his 1100 (3-flute 1/2" Carbide EM in 6061, 5000 RPM, 0.1"WOC, 0.4"DOC) is only about a 0.84HP cut, so below the power where pullout would be an issue even on a rather poorly adjusted Tormach PDB, but still beyond the capability of the 440. So, still does not really compute...

Regards,
Ray L.

[tbev]

I understand what your saying. The easiest way I can explain it is that the single cylinder on the 440 PDB compresses my factory 1100 Belleville washers. That leads me to believe the holding power of my 440 PDB, using the Tormach washers, will be close to that of the factory 1100 PDB, which is more than enough for a machine with what, half the HP.

[SCzEngrgGroup]

I understand what your saying. The easiest way I can explain it is that the single cylinder on the 440 PDB compresses my factory 1100 Belleville washers. That leads me to believe the holding power of my 440 PDB, using the Tormach washers, will be close to that of the factory 1100 PDB, which is more than enough for a machine with what, half the HP.

Sorry, but that logic simply does not hold water. The design target on the Tormach PDB was 2500# drawbar tension. The release force is even greater, and requires compressing the springs to almost flat. A single stage cylinder operating on 100PSI simply cannot provide anywhere near the force required to do that. That is simple, basic physics. The 440, with a 0.75HP spindle, clearly requires less drawbar tension that a 1.5HP 1100, so you likely need something more on the order of 1250# for the 440 to provide performance comparable to the PDB on the 1100 (and the 1100 is not immune to pullout). But your air cylinder provides barely half that force. This is an area I know a little about, since I design and manufacture power drawbars and toolchangers for TTS systems, and I've done extensive testing over many years to develop a TTS PDB that never, ever suffers from pull-out on 1.5HP machines. My PDB provides ~3500# drawbar tension, by actually torquing the stock drawbar to 30+ ft-lbs, without using any Belleville springs, which is why it's unaffected by chatter. I can tell you from my own testing that what you have may "work", but will not be truly robust, as the math simply does not add up. Add in chatter, and I can pretty much guarantee you will see pull-out. A 3" 3-stage cylinder will get you where you really need to be if you want it to be absolutely bullet-proof.

Regards,
Ray L.

[nitewatchman]

I understand what your saying. The easiest way I can explain it is that the single cylinder on the 440 PDB compresses my factory 1100 Belleville washers. That leads me to believe the holding power of my 440 PDB, using the Tormach washers, will be close to that of the factory 1100 PDB, which is more than enough for a machine with what, half the HP.

Please don't misunderstand my comments.

I think that this is a good looking, functional drawbar.

gary

[tbev]

I don't know what else to say besides I'm using it, it works. I'm not trying to make a bunch of money, I'm simply not going to deal with manual tool changes, I spent a lot of time a money figuring out the best setup. If it was giving me any issues I certainly wouldn't be selling them to anyone else. The issue I think your having the most trouble with is assuming it's a 3in cylinder, it's also not some chinese built piece of **** cylinder. I'm having them custom made, but the fact of the matter is it makes more than enough holding power. I sold 14 of them and a couple people at least will probably make videos or at least provide feedback. Again, if I wasn't sure everyone would be more than happy with their performance I wouldn't be selling them.

[kstrauss]

The issue I think your having the most trouble with is assuming it's a 3in cylinder, it's also not some chinese built piece of **** cylinder. I'm having them custom made, but the fact of the matter is it makes more than enough holding power.

What is the cylinder size? A 4-inch cylinder would supply 77% more force than a 3-inch one.

[SCzEngrgGroup]

What is the cylinder size? A 4-inch cylinder would supply 77% more force than a 3-inch one.

Which would put it exactly in the range I suggested for that machine....

Regards,
Ray L.

[tmarks11]

I sold 14 of them and a couple people at least will probably make videos or at least provide feedback. Again, if I wasn't sure everyone would be more than happy with their performance I wouldn't be selling them.

Congrats. That's awesome.

I would suggest that you offer Tormach to let them sell your drawbar (which is how some of their other mill accessories came into existence), except I am sure that they already have a design in the works from the company that makes their other PDB. Hopefully for you, it will be as slow coming to the market as many of their other accessories.

[tbev]

Which would put it exactly in the range I suggested for that machine....

Regards,
Ray L.

Yup. I hope you know I don't take offense or mean to be rude at all. I'm always down for constructive criticism and I've always appreciated your thoughts, and all the help you've given me in the past.

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