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Hugh McDonald Steel Rolling Mill


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Regarding the sintered bronze i do not know if it will not stand the pressure.
Regarding ball bearings i have seen several (like DIDTAS, Old Guy and The BLU Crusher) using them to the upper rolls. Pressure should be the same.
If talking high pressure suppose roll/needle bearing would be the best .
Staying to the original design is of cause good. But i'm having a hard time to finding bronze to a reasonable cost nearby. And then a redesign can be appropriate B)

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Have made som reserch: :D

Sintered bronze can stand 10-20N/mm2 and redmetal (bronze) can stand 60 N/mm2 in dynamical force (velocity <2 m/s)
For static force it is 50 N/mm2 (redmetal 90 N/mm2) (for velocity <0.01 m/s i have 0.02 m/s)

For my case the roller should stand for 1630 kg (3 593 pounds) dynamic
Or 4073 kg static (8 979 pounds)

Sombody that have an idea about the force.... :blink: for a 2" roll

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Doesn't matter the force between the rollers, the force that you can generate with the mechanism is what you are interested in and can more easily calculate. After calculating this you can select a bearing based on the the load from a manufacturer lookup table in a catalog.

The failure load of the rollers should by much much higher than the the load the machine can generate, which is why the force between the rollers is unimportant other than it is the same as the force the mechanism can generate, and is about twice the design load of the bearings (2 bearings per roller, divided equally) or you can use the force generated as the design load for the bearings as a built in safety factor of 2.

How much were those plans delivered? They are starting to look cheap.

Phil

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Hmmm
Hard to calculate a force....
Backwards calc the "original" bronze bearing will stand 7637 kg for max dynamic design (failure is another thing this is calculated for higher speed design and usage a long time)
Maybe start looking after some solid bronze

No comments from anyone using ball bearing for the upper roll. Supose the force should be similar or greater on this one due to that the drive is on this one and rolled metal is plastic...

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Have changed the plans, I will use solid bronze instead.

But at as i didn’t get it i decided why not try to cast it. That could be a fun mini project
Looked at several different mixtures decided to use 15% Sn as i only had tin for old tin soldiers. It had also 5-10 % lead.

So the mixture will be 85% Cu, 15% Sn and 1% Pb


post-14765-0-03676200-1319209220_thumb.j

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one possibility for making a bronze bearings would be to make a large steel block and drill a hole large enoughto receive a bronze bearing. Then using oxyacetylene fill the hole with brazing rod and then bore out to size. If the two units were clamped together for the drilling and boring operation then they would be in alignment. It is also possible to place a piece of steel rod or indeed a piece of steel pipe in the centre of the hole to minimise the amount of brazing Rod consumed. This results in a bearing surface fully bonded to the bearing block and it is renewable in the future using only the capability of one's existing facilities. There are a variety of ways to get an acceptable bearing surface and sizing. Probably a lot of people attempting to build one of these machines will have access to a lathe, so boring out with the blocks mounted in a four jaw chuck is one method or alternatively mounted to a faceplate. Also one could make a boring bar and mount the bearing blocks to the cross slide. If one is restricted to just a drilling machine and one cannot getI the exactly the right size hole or a good enough finish then the bore can be enlarged to size with adjustable reamers, or by hand scraping. A triangular scraper for this purpose can be made from an old triangular file. I would suggest that bronze bearings are very appropriate for this type of machine both for their compactness and high loading capability, also robustness in the face of high-temperature if the machine is used on batch work and the rollers themselves start to get hot.

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The lower bronze bearings is ready :D
The reson for having these round is that the axis i fixed and the bearings i in the roller for the lower one.
The top could be rectangular. But i think i will go for ball bearing for the upper roll as seen in here before.


Los pictures B)

post-14765-0-79659900-1319472320_thumb.j

post-14765-0-40788200-1319472268_thumb.j

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  • 3 weeks later...
  • 3 months later...
  • 1 year later...

Hiyah folks,

 

I'm planning a rolling mill, in the style of those plans you'll see by that fella in Australia, Hugh McDonald. I have a little different setup though. I've got my hands on two 3-phase motors, one built into a gearbox. The plan is to use the other motor as a three-phase generator, somehow from the single phase, to run the mill. I have wired 3-phase projects in lab, but I'm in the dark on how to build a3-phase  generator out of a motor. Have any of you seen or done this?

 

Haha, either way I realize I'm on a smithing forum, so I'll move on to other questions. Have any of you built the McDonald mill? I've been looking for details about the foot-pedal and lever he uses, and I'm not keen on paying for plans unless I'm absolutely sure I'll use them (forgive me if I sound cheap, it's a school budget). If you have the plans, are they engineering drawings or a "how-to" book? I'm simply asking what the quality of the plans are, I guess.

 

Thanks a lot fellas, I figure if anyone will know answers it'll be someone on here.

 

Matt P.

Essayons

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What you want to build is a "Rotary Phase Converter" .   I built one for my Gorton Vertical Mill.   Start off by Googeling " rotary phase converter circuit diagrams.

 

There are basically two types with varing  degrees of sofistication.  !.  RPC with self starting circuitry.   2.  RPC with manual start.  The second choice is the simpleist to build because rather than including a complicated electronic starting circuit this type uses a pony motor or maybe even a pull start rope like an old outboard / lawn mower .   The Rotary phase converter (3 phase generator motor) is started by either mechanical means or electronic starter circuits.   It is run using single phase 240v power .  After it is running the third phase is tapped of of the windings and  can be used to power another machine.

 

I think that the " Practical Machinist" site has a lot of information  on various RPC  builds.   One thing -  The RPC generator motor needs to be over sized or bigger than the rating of the driven motor. 

 

The good news is that it really works.  I will post a picture of mine tomorrow.  Maybe I still have some references around although they were on my old computer that crashed and burned.

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Knots, that did help, I confused some of the nomenclature on the rotary phase converter, so the redirection led me straight. Making a capacitor start doesn't seem too hard, I've done a few similar jobs on a belt grinder and a drill press. Otherwise I've seen a pretty cool rack and pinion pedal start that slides off once it starts. Either way.

 

steve, I sifted through em before, and not to much avail. Using hydraulics would be cool, but that's next semester, haha. 

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Have a look at this forum.   You should join and lurk - there is a wealth of information available.

 

Making a 3 Phase motor start on single phase power is not as straight forward as adding a couple of start capacitors, at least if done properly.   Have a look see and see what you think. 

 

http://www.practicalmachinist.com/vb/transformers-phase-converters-vfd/

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I have made a rolling mill using the Macdonald plans. They are useful in getting everything together but are designed for you to finalise. Due to sizes of  available stock. Most of the measurements are in imperial but some are metric.

If you can design your own mill now you won't need the plans. If you need to ask some questions then I'd get a set. One point to design in is a slip point or shear pins. You will stall the mill and using a gearbox attached to the motor sounds like a good way to grind the gears up.

Andrew

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I found an excellent post on  foggs forum

 

A lot of good detailed pictures and I'm glad. I don't think I need half the things in the McDonald design, and what's cool is someone use three-phase. They used a variable frequency drive instead of the generator I'm trying to make.

 

knots, I did join the forum and I've siphoned through the thread on the rotary converters. I've got some EE friends that will love to sink their teeth into this project. It's complicated, but not too bad. There's starting, running, and balance capacitors, all of which sized we've had kicking around. 

 

Bottles, which did you use, a slip joint or shear pin? And how often does it jam? I figure a dead man switch would be better for safety, but a shear pin seems pointless unless I can calculate the margins of the forces exerted. I think my gear box has its own precautions, but the way its built I'm under the impression that the posts it would be bolted on would rip out before the gears slipped.

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Hi steamingpuds,

My mill uses a 3hp motor geared down  to about 80rpm that then uses vbelt pulleys to take it to about 20rpm. This isn't elegant but motor gear box and pulleys were very cheap off evilbay. The motor is held down giving tension to the v belts. I have had to loosen the motor to allow them to slip. I have been using this for a while and occasionally still stall the roller. No mater how much you think you won't stall this you WILL. Build in some fail system just in case. There is a lot of torque in this

I have the lever arm and turn screw. I do find using the arm helpful just as a quick change of thickness and the possibility of tapering. It doesn't take that much work and if you find you don't like it push it back and ignore it.

I have also used a VFD to control the speed. I havn't found much difference in speed but the motor sounds happier at about 65HZ then the 50hz it should run at.

I'll try and get a picture to show my mill later.

Andrew

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  • 4 months later...

I have been meaning to make one of these for ages. The design inspiration is from the McDonald Mill using the material I had.
 
 mill-p3_zpsb5f37fc7.jpg
 
 
mill-p2_zps9cda732e.jpg
 
 
mill-p4_zpsdc9e81bd.jpg
 
 
mill-p1_zps6fa0e2e9.jpg
 
 
 
The 3 phase, 3hp motor is running at 1400rpm through a 100/1 reduction box. The sprocket on the reduction box has 17 teeth running a 5/8" chain to the top roller sprocket with 57 teeth. The rollers are 50mm and run at about 29 rpm, whch is about 14 feet per minute.
 
The idea for using the inverter, which I already had was so that I can control the power the motor will take and not overload or break the mill. Also to be able to adjust the speed it runs at, but 29 rpm seems just right.
The only job I had someone else do was to fit a phosphor bronze sleeve in the bottom roller to take the 1" shaft. The bottom roller carriage is made from 45 x 20mm bar. Just in case you are thinking about safety, it does have a full chain guard. It has also been made so that it comes apart and the frame breaks down in to 5 pieces.
 
Mick.

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