Babbit pour - Drummond M leadscrew

Been wanting to do this for a while because the biggest Dummond weakness is its silly leadscrew nut system. It's sort of clever, but too clever for an average bodger to sort out

So you take out your LS nut arm, it can be removed at the LS handle end with some jiggling and fiddling

This is one where I carved the remaining nut threads out for an aluminum insert, I have drilled extra 4mm holes on each side to act as lugs for the babbit pour

Then we use our secret ingredient for the mould

PINKGRIP

It didn't even smoke when I poured the babbit and it can still be peeled off 24 hours later, I left mine overnight to harden before the pour

After a few days it turns into rock hard plastic so don't leave it too long

Next up, the most important bit

Wait for the missus to go out because you need the kitchen gas cooker

This is the foundry, a dessert spoon, a stirring rod of steel, thick gloves and a pair of glasses

Put the LSarm into one of those cheap modeller vices, a tenner from Lidl, and balance the leadscrew into the pour zone

Use the steel stick to remove/push away impurities so you have a nice molten silver spoonful to pour

Then go for it!

Let it cool then gently tap the LS arm free

That is a jar of pinkgrip squirted out of the tube and kept in a jamjar

Edited By Ady1 on 29/09/2022 11:58:59

Got to tidy it up later and try fitting it back in

It's my first ever pour and things could be better but the basics seem to be sound so far

All my piccies are here

Edited By Ady1 on 29/09/2022 12:04:09

That is just too cool !

I purchased some babbitt, but have not used it yet for bearings.

I found some high-temp putty ("high" being relative to molten babbitt temperatures), and have not used that either (I am waiting on retirement to shift into high gear, and use all the materials I have purchased).

I played around with casting some small parts with babbitt, just for fun, but got an incomplete mold fill on some of the parts due to the low temperature that babbitt is poured.

Great solution.

Thanks for the pictures.

Edit:

I have heard that sometimes the inside of the bearing shells are tinned, to help with babbitt adhesion.

.

Edited By PatJ on 29/09/2022 12:05:36

VERY GOOD ! Better detail may have been possible with the lead screw warmed up a bit . making a closed mold and then feeding with a runner would also help to get better detail due to the head pressure. Never the less your method is quick and simple ! Noel.

Very impressive Ady!

I have done a similar job on a steering box. I used blacklead grate polish as a parting medium for the screw and Gungum exhaust repair for sealing. The latter was not completely successful, so very interested in the Pinkgrip - is that the builder's quickgrab adhesive available at toolstation or screwfixx? Why was it necessary to decant it into the jar?

My own efforts are on my Flickr album here and subsequent pictures

https://www.flickr.com/photos/140734312@N06/42830514132/in/album-72157669955074511/

Despite heating the screw, I did not get a complete fill, which I think was due to leakage, hence my interst in the Pinkgrip.

Martin

Pinkgrip goes off once you pop open the tube

I had used that one for a front door fix then decanted what was left from the tube to a sealed jar so it could be used for other jobs

It does the job. quite adequately.

Improvements might be to not machine through the metal base - divots would retain it adequately. Tinning the surface would also provide far more adhesion to the casting. They wear so slowly that it may well last years, but raising the thread from the casting would allow a thicker bearing depth and subsequent longer life - if the individual threads become separated and are not too well affixed (to the base metal) they could peel.

Not criticising - just making suggestions for improvements next time.

Fitted it this PM and it's great, so that's a headache problem solved forever

Tinning

Tinning in this instance refers to putting a thin coat of solder onto the job prior to joining

tinning

tinning

Edited By Ady1 on 29/09/2022 16:28:48