Crash...bang....5900 variable speed master cylinder

[Tim9]

So... I was using my 5900 and when I was turning the variable speed control I heard a pop. Variable speed was kind of locked. It actually felt like it turned too far. This had happened before and I’ve honestly never been able to figure out what happened. I end up disassembling everything and then putting it back together. Then it works. It feels like the cam that contacts the roller push rod turns too far. I know that there’s a roll pin which prevents it turning too much but I haven’t been able to see anything wrong with the way I have this put together.
So...I unbolt to top dial....take out the main clock-spring...and unscrew the 4 bolts attaching the master cylinder bracket to the lathe.
I then unscrew the hose. Inspect. And unscrew the set screws from the master cylinder bracket which attaches the cylinders. Everything looks ok. I put it back together. Start up machine and run it up to speed. All good. Then about ten minutes later...add a little more oil...and again start turning up to speed. AND CRASH. I’m looking at the master cylinder hanging out of a shattered cast iron bracket.

by the way...just a note on this picture. It’s a picture after I tried brazing it. You can see a couple of spots where it stuck. But I wasn’t getting a good flow around the cracked pieces. I should have tried a rosebud. It’s probably been a year since I last brazed cast iron. Like everything....practice makes perfect. I should have practiced my brazing before attempting this. Really am out of practice with my O/A skills.

 

[Tim9]

You can see the cracks in the housing and three broken chunks in above post’s pics.
My first thought was that I must have not fully tightened the two set screws. The crack broke the cast iron between the two set screws. It’s just shattered. And without it, no lathe. I first tried to braze it but didn’t have much luck. But I didn’t clean it that well. And the reasons I tried it that way is because if I ground all three parts... they just wouldn’t stay together at all. Anyway it’s a catch 22. Don’t clean it and it doesn’t braze well. Clean it well....and it doesn’t stay together so you still can’t braze it. So after that fail....I bored out a 2-1/4” steel round so it fit a tiny lose around the housing.
I arch welded the steel ring to the outer housing and the cracked cast iron pieces. I didn’t take a lot of pictures...sorry about that. I used nickel 99 rod. I really love that stuff. It flows wonderfully between the steel and cast iron. And machines pretty well. It’s more expensive that’s the nickel 55.... but the nickel 55 just is a bugger trying to machine. And most of my welding of this was front of the housing. This area had to be machined flush afterwards since the master cylinder sits flush against it. So nickel 99 it was .
Screwed one 5/16-18 bolt into which also was threaded through the ring I made.

 

[Tim9]

It ain’t pretty. But then I mounted it in a 4 jaw chuck...cleaned it up in back gear because it was awkward in my SB 9” lathe. Didn’t want it spinning fast.

 

[Tim9]

Like I said....not perfect but usable. I then drilled two more 12 x 1.5 metric holes for the other set bolts.
The finish looks really ugly...but this housing was clamped in the 4 jaw chuck....clamped on the square end of the housing. I had to put two aluminum spacers between the chuck jaws and the housing to cover the slot. And the other side where the other two jaws made contact....when I clamped the jaws it would compress the housing since it’s slotted. It just wasn’t the most secure mounting in a four jaw chuck.
So, I put the lathe in back gear and was probably around 120 RPM. Used a carbide bit,,,,and took light cuts. Just to clean it up a little. It’s ugly but usable. Oh well.

 

[Tim9]

Now here’s where it gets interesting..

I bolt it up and I couldn’t connect the hose. That’s when I found out why it crashed. The second picture shows the hydraulic hose wrapped around the pulley. The last picture is where I was trying to show in the picture the hose. My thumb is touching the hose. Kind of hard to hold the camera, a light in my mouth .... and then touch the hose and take a picture

 

[Tim9]

So....in the pictures in the previous post...it looks like what happened is that the hose came loose from its support bracket and wrapped around the lower motor pulley. Ouch. So I made a little extra support clamp out of plumbing hanging strap. Here’s the finished product. Alls well that ends well.

 

[Old Mud]

Tim, i'm glad you got it all sorted out. But i have a question. Maybe im not seeing something there but how will you change that belt ?

 

[Tim9]

I never had to change the belt. When the master cylinder was connected before the crash, the hydraulic system would have had the pulley tightened against the belt. In the picture, the hydraulics had been disconnected for a day and then the following day is when I was reinstalling the repaired unit.
So what you are looking at in the picture is the lower pulley totally retracted so to speak. The belt is therefore very loose since the hydraulic cylinder has drained and backed off. And the hose is wrapped around the lower pulley.

All I did was unwind the hose....rotating it in reverse of how it got wrapped. Since it wasn’t connected to either the bracket yet or the master cylinder....it was easy to unwind it. Then I secured the hose properly to it’s bracket....which is that rod sticking out in one of the pictures. I attached the hose with the original two piece clamp and wrapped with an extract little length of plumbing strapping.
Then just had to connect the upper hose connector to the master cylinder and run it through the process of fully turning to highest speed....hold there a few seconds.....and then back off to lowest speed.

Anyway, I was totally dumbfounded at first. I couldn’t understand how a loose set screw could cause such a Catastrophic crash.

 

[matthewsx]

So, what you're saying is it's lucky you have a lathe to fix your other lathe

Cheers,

John

 

[Tim9]

Just a side note about cast iron. It absorbs oil into its porous castings. I knew this and in all honesty I should have baked the casting in the bar-bq pit for a couple of hours before trying to braze. It. But, I really repaired this as an afterthought. When I first crashed it I was distraught. I went on EBay and snatched up a used one because I remembered seeing it in the past from a recent seller who was parting out a 5914.
So I ordered it.... 45.00 bucks but hey...the lathe is scrap without having a speed control. It’s a single phase model....so I’d have to change the motor and then add a VFD....then fix a fixed lower pulley. So it was worth 45.00
But after ordering it....I was still concerned. I just couldn’t believe it crashed. I didn’t know about the hose yet. So I figured I’d repair the old....and see what’s going on with the cam on the speed control bracket. I figured if it crashes again...then I’d have the other I ordered from EBay. And mind you, when I use the word crash, at the time it was more of a thought that the cylinder would pop out. Because I didn’t know about the hose. I actually thought the cam must have been pushing so hard....loose set screws and cam action had cause the broken cast iron housing.
Anyway.....you and I can both see all of the oil which baked out of the castings while welding it. And that was after I tried brazing it. So...if I had to braze it...cook it first...then grind and then braze. But this was a hack. And I wasn’t too concerned with it since a new old one is on the way.
But I doubt I’ll need it now. Because this looks good to go.