Re-Birth of an EPCO 60 Ton Garage Press

[awemawson]

Several years ago, I was looking for a 'parts washer', won one on eBay, and speaking to the seller to arrange delivery by pallet, he asked if I was looking for anything else. Well I was - I wanted an 'H Frame' garage press, preferably hydraulic. He almost burst into tears and told me the tale of his press. It was his pride and joy and in superb condition, until he had a fire in his workshop. As he had oxy-acetylene cylinders in there the Fire Brigade wouldn't let him enter to save anything, but just let the lot burn, dowsing down as it did.

Eventually the wreckage was pulled out into his yard, and the remains of the press sat there in the rain gently rusting away 

Well says I - is the framework still sound - perhaps I can use it as the basis of making my own press. Long story short, I bought it for scrap, he jammed the parts washer into the framework of the press and it all got delivered to my place. It must have been a very intense fire. The aluminium motor frames for the hydraulic pump and platten raise / lower motor had melted and dribbled away 

[awemawson]

Now the frame didn't look too bad - one of the channel sections was slightly warped, but after all it would be in tension in use.

The platen that you press against is suspended from four enormous acme threaded rods that are chain linked at the top, and run in bronze nuts in the platen itself. Fortunately when the fire happened, the platen was pretty well fully down, and I was able to raise it with my forklift, exposing the bronze nuts, which were absolutely and completely rusted solid. Huge chunks of bronze about 3" square and 6" long so I didn't fancy making new ones 

A bit of research on rust removal methods introduced me to Citric Acid. Rust is bigger than the steel it is formed by, by 7 times the volume, so a little bit of rust will jam threads nicely. Anything you use to de-rust needs to be able to penetrate between the two parts and form a compound that is soluble in water so that gradually things migrate out of the gap. Citric Acid forms Iron Citrate from rust, and this is water soluble. Phosphoric Acid for example, which is a common rust remover, forms Iron Phosphate which is not water soluble and still jams your parts!

Plastic buckets with warm citric acid solution were put under each threaded rod and raised to immerse the bronze nuts. It took several weeks of re-warming and replenishment before eventually I could undo all four nuts.

Then the threaded rods were removed, and put in a capped length of 110mm soil pipe again filled with citric acid. Several days later I had threaded rods and nuts that were perfectly usable 

While this was going on, I removed the original hydraulic cylinder with a view to seeing if it could be saved. A might heavy lump of metal 

A few pictures were taken :

[awemawson]

That cylinder took several days to dismantle. You can imagine - the hydraulic oil had all boiled off making goo, and the seals had melted into the end cap threads, so it took forever to just unscrew the end cap using heat, cold and much violence - look at the lugs on the end cap and see how they've been abused. It was not a pretty operation 

However, off it came. I eventually found a place in Scotland who claimed to have the right seal set to re-build it, and after the exchange of quite a bit of hard earned cash they arrived. This I think was the first hydraulic cylinder that I'd ever dismantled - nothing like choosing a problem child.

Piston end wasn't too bad, but I made an expensive mistake with one of the seals in the end cap - remember - lip towards the pressure - well I forgot, put it in the wrong way round, screwed it up taking it out, spent more hard earned dosh on another one 

Amazingly the chromed rod wasn't too bad, and after honing the cylinder bore came up quite satisfactorily.

[awemawson]

The original hydraulic pump was toast - just a block of rust filled with aluminium that had dribbled into the chamber when the motor melted. So the hunt was on, but this press needed a very high pressure. 5" cylinder bore 60 tons = about 7,000 psi

Eventually eBay turned up an Enerpac 240 volt three phase unit complete with a solenoid valve set suitable for a double acting cylinder 

So now to look at the platen lifting arrangement.Those long acme threaded rods sit on thrust bearings cleverly arranged with huge springs such that when the press is unloaded they balance the weight of the platen and they rotate on the thrust bearings. However when the load comes on the press the springs compress and the load is taken by shoulders on the rods that rest on the framework. Nice bit of design.

Initially I couldn't work out why my nice new motor, chain drive and cogs hadn't got the guts to rotate things, until I realised that the intense heat of the fire had softened the springs and the bearings were not being used. Careful measurement of the wrecked springs gave me dimensions but not a 'spring rate'. They need to support the platen 'plus a bit' so I weighed the platen (about 100kgs iirc) and had springs custom wound to 1/4 of that when compressed from 1/4" spring steel rod - seems to work 

Then it was a case of a bit of grit blasting and spray painting:

[awemawson]

So putting it all together, and doing a bit of wiring and plumbing, it turned out like this:

[awemawson]

Now all that happened in 2010 / 11

So how did it turn out. Well OK'ish - it certainly pressed things, but I was never convinced that it was working correctly - I had a strong suspicion that the piston was 'letting by' and not developing the force that it should, and the end cap seals started leaking - first just a drip, but obviously getting worse week by week.

Time for a decision ! I decided a couple of weeks ago to re-build the cylinder AGAIN. I've had a bit more experience since then with hydraulics and perhaps now know more questions to ask of seal suppliers 

As the cylinder is so massively heavy I decided to try and do it 'in situ' and make a 'flogging spanner' to undo and re-tighten the end cap that had given me all that bother before.

Basically this is a 6" ring spanner with lugs to engage the nut, and a flat to hammer against. I wanted to aim for a tight fit, so it could be hammered on and stay in place while being used.

This is the CAD drawing I generated to cut it on the Beaver Partsmaster:

[awemawson]

I had a bit of 12 mm plate that is somewhat tougher than mild steel - no idea what it is - and it all went quite well until it broke loose from it's hold down clamps. Not a big issue as the 'overcut' didn't stop the spanner working.

[awemawson]

After a bit of titivating with a file it fitted nicely - just tight enough to stay in place when tapped on with a mallet 

I knew that the piston would be a bit of a pain to pull out, so I turned up a spigot (with a cross hole for pulling) to go in the hole in the end of the ram, with a recess to engage the locking bolt that holds tools on the end of the ram. Now this is where later on it turns out I made a BIG mistake. I made the spigot out of what was to hand - an old worn digger pivot pin that was 55 thou too fat, so got turned down.

Why a big mistake - because as at some point I must have pressed down with the ram, and got the spigot pressed beyond it's shoulder entering the 1.5" bore with its 1.555 diameter shoulder 

It was absolutely thoroughly jammed, and not only that, managed to expand the end of the ram by 2 thou making taking off the end cap past the 'bulge' a right pain involving hydraulic pullers and much perspiration

In the end it came off - but how to remove the spigot? It became rapidly obvious that I had only one option - mount it up in the lathe, slice it off and bore it out 

It's a big lump to mount - obviously had to be on a fixed steady , but then the only place I could grip it in the chuck was on the threads of the piston cap retainer - not very nice, but aluminium pads saved the threads from destruction.

In the end it proved I'd managed to press that spigot in 20 mm beyond it's shoulder - no wonder it was jammed, and says something for the power of the press that it did that when weak and in need of new seals 

It did however mean that I had no problem using the spigot to pull the piston / ram assembly out as intended !

[awemawson]

Now at last the new seal kit arrived, and sure enough they are not the same as the previous 'new seal kit' that I fitted back in 2010. The cap end was identical, but if you look at the piston, the double acting seal has a pair of nylon 'wear pads' either side. The previous lot were wider axially than the gap left when the piston end cap is fully home, so were being squashed by the cap. The latest set are the correct 1.75" wide (the others were 2") and sit snugly when the piston end cap is fully tightened and locked with it's grub screw.

I had to hone 2 thou off the outer end of the heavy chromed ram to let the cylinder end cap fit nicely. Then we were ready to push the assembly back up into the cylinder body.

[Joules]

Very nice, I have some Brazil nuts I can't crack ?

[awemawson]

How flat do you want them 

So - how did it do this time? Well I had some teething problems, not realising quite how the Enerpac worked - details here:

http://madmodder.net/index.php/topic,11434.msg133905.html#msg133905

But the new (new) piston seals are now NOT letting by, and it seems to be working as it should. Tell you more after a  few weeks of use 

[awemawson]

I finally got to the bottom of why the cylinder 'end cap' was weeping. This seal is basically an 'O' ring in a groove on the outer of the male thread that screws into the bottom end of the cylinder.

When I dismantled the cylinder originally, in it's fire damaged state, the O ring was charred to hard carbon that crumbled as you handled it - as near as I could measure it in that state it was made from 1/4" cord. So I ordered up a "five inch bore by 1/4" O ring" Well it seems that what I was supplied with was a 125mm x 6mm one - close but not the same  Talking to various hydraulic companies I was advised that from the vintage of the equipment and the fact that all other measurements check out as Imperial it was most likely supposed to be a "BS429" O ring which is 5" bore and 0.275" cord. Now 0.275" is entirely in line with me assuming 1/4" from the charred remains, but is essentially 7 mm so 1 mm fatter than the one supplied and fitted.

That thumping great spanner that I made came into use again and I fitted the fatter O ring. Lo and behold - no leaks 

As you can see in the photographs they don't look very different.

[awemawson]

So buoyed up by that success I decided to tackle another nagging issue. The four 1.5" acme screws that the platten is suspended from are not entirely straight - probably distorted in the fire - but they work. However when the platten is fairly high, so a long length of the screws dangles below, they tend to thrash about as they rotate. Maybe the rotation speed is a bit too high, but its a synchronous 3 phase motor so it is what it is!.

I had intended to cut oak blocks with a hole bored out to sit the base of the screws in just to stop them thrashing, but when I was clearing out a cupboard, I came across a pair of 1.5" self aligning pillow blocks that I must have had for decades - brand new in their boxes. Now if I could find another pair I'd be sorted ....... well eBay provided at a very modest price, so they got installed as per the pictures below.

A slight complication is that (as referred to in a posting 'up the page' ) when load comes on the platten, initially the platten and screws descend about 1/4" as the spring mounted thrust bearings have the load transferred from them to the main framework. This means that the screws cannot be fixed in the pillow blocks but must be able to slide a bit.

[awemawson]

Now of course, if I had a press I could straighten the screws, but if I take the screws out I don't have a press  One day I will make up a dummy screw from solid rod, and take them out one by one and straighten them - but it's a major dismantling job to get them out.

So another thing that I wanted to sort out was a calibration on the pressure gauge in 'applied tons' rather than just PSI. But as this sort of gauge (10,000 psi don't forget) is sealed and oil filled, it isn't just a case of opening it up and fitting a different dial. So I decided to make a suitable chart and fix it close to the gauge.

I went though various materials to engrave, and they all were unsatisfactory in one way or another having either a slightly rough finish or were too soft  until I hit on 'Rear engraved PetG'

Clear PetG plastic is what I had bought to make a new bezel for the gauges on my JCB 803 excavator so I had some in stock. I wanted a black background with lines & lettering that were easily readable so this is what I did:

A: I spray painted a square of PetG with Matt Black paint

B: Then when it was dry I laser engraved a mirror image of my chart through the paint into the plastic.

C: Then I sprayed the engraving all over with my line colour - orange as I had a can left over from making some boxes for the Traub rebuild

D: Then as the graph was being fixed onto a previously painted surface I covered it in talc to hopefully stop the two paints sticking together over time

And this is the result - I am really pleased with it and will definitely use this technique in the future.

(Shiny black objects are confoundedly difficult to photograph!)

[RobWilson]

Very professional looking chart Andrew 


Rob

[awemawson]

Thanks Rob for those kind words.

I've finally got round to doing what I'd planned back in 2010 when I first got this press - to fit upper and lower limit switches on the platen. Without them, if you go too high the screws jam in the nuts, and if you go too low the platen falls off the screws 

I'd bought the limit switches back then but hadn't fitted them for several reasons. Firstly I knew I still had things to fix on the hydraulic side, but mainly I was a bit stumped how to use a single pole limit switch to stop a three phase motor without introducing the complication of extra contactors and relays.

Then I hit on a plan - it's blindingly obvious once I'd thought about it. Put them in series with the 'stop / start / overload' unit.

The circuit below shows what I ended up doing - I'd initially thought that once the limit had been reached, I'd need another button to over ride it to reverse off the limit, I even mounted one and made a nice label. Then I realised that pressing the start button would pull the contactor in (but not hold in), and while still pressed the motor could be run off the limit

So I substituted a grommet for my button 

[awemawson]

Now I wanted to mount the limits to the rear of the machine out of harms way, but the platten doesn't project far enough backwards to strike the switches, so I had to mount a protruding block.

Now I always have great difficulty free hand drilling and tapping holes for things like this - they always end up squiffy. So I first made the block with tapping size holes and used it clamped on as a jig to ensure that the holes in the platten were drilled perpendicular and in the right place. Then I drilled out and counterbored the block for final fixing

[awemawson]

Then we needed a junction box to connect everything up

[awemawson]

And to fit the limit switches themselves - I left about 1/2" of extra travel to be on the safe side

[awemawson]

Then it was just a case of wiring it all up.

Perhaps I should explain, the platen motor which is 3 phase, has an overload contactor that doubles as a start stop swich. But when pressed 'On' although the contactor latches 'on' the motor doesn't run until you press the 'Dewhurst' reversing switch either 'Up' of 'Down' - it is spring biased centrally.

[awemawson]

So now, if you inadvertently run the platten onto one of the limits, the contactor drops out preventing the Dewhurst switch being used.

To back off the limit, you press the green start button, and at the same time operate the Dewhurst switch to back off the limit - it works really well.

[Spurry]

Yet another great job Andrew, well done. 
Pete