Re-babbiting big end bearings

[Phil Kingdom]

Here is a link to for a Myford con rod boring jig, http://www.lathes.co.uk/myford/page3.html  they are quite rare but do come up once in a very blue moon on e-bay.

[Ruairidh Dunford]

Some further info that has been emailed to me tonight:

“This thread started by Greig and added to by various people has landed at just the right time for me and has already answered some of my questions.
Attached are a couple of photos of the Con-rod re-metaling mould / jig I made.
This idea really started with some idle time in the workshop, a conversation and nothing else to do.
As can be seen from the photos it is basically in two parts.
The Base, this is a piece of Ground Stock Bar 9x1x3/8”there is a ½” diameter “Gudeon Pin” fitted to one end. The pin was reduced to 3/8” and screw-cut to BSP with an undercut at the shoulder. The bar was threaded to match with a light ½” counter-bore. I use a Tapping Attachment to ensure it is exactly square. Obviously a guide block or drilling machine could be used. The idea behind this was to use it as a check and make sure the con rod was not bent. By putting the cleaned rod onto the Pin and allowing the rod to lie against the base it can be easily seen if it is true and adjusted to suit before any further work.
The Mould, the main part of the Mould is made from Cast Iron. I used an old window weight for material. It is usually an open grain “dirty” material and they can be found at most joiners workshops. The idea for using Cast Iron is the Babbitt is less likely to stick to it. I made two 1 ¾” flanged pins 1- 3/16” diameter keeping the flange ¼” thick and milled them to the exact centre line. These were screwed to 2 mild steel plates 2-3/8 x 1-1/2 x 1/8”with the big end bolt holes accurately pitched. The main reason for making 2 parts and machining to the true centre line was to make it easier to find the centre of the big-end for machining ie not oval on assembly. Also both halves can be poured at once.
On assembly, before using my intention is to dust the Cast Pin with Graphite powder or rub over with a joiners pencil to prevent sticking. It will be seen that the base is not absolutely necessary when in use, but my thoughts were, it is a secure way of holding in the vice with a piece of insulation under the Cast pin to minimise heat loss.
I am working on a way to machine the sides of the con-rod after building the sides up. Obviously it must be central and true to the rod axis. I think we are almost there!
Now for a question, what flux to use for tinning my thought was Baker Fluid (Killed Spirits)
I hope the above ramble makes sense and may be of some use.
Tod”


   

   

   

[Ruairidh Dunford]

And from John Williams:

   

   

   

   

[john williams]

Further to the photo's of my re-mettaling jig.
 This is a jig that was produced for the trade, and I rescued from a Technical college.
Dimensions; The half round casting bar is 1 3/16inch across the flats.
The casting bar protrudes 3/16inch each side of the side pieces.
Distance between side pieces when clamped together 1inch.
 Side pieces 1/2inch wide with the internal shoulder 1/4X 1/8 inch
 I do not wish to teach "Grandmothers how to suck eggs", but this is the method I was taught 40 years ago.
Firstly the big end assemble must be completely grease/oil free. Wash with degreaser, then soak in mixture of boiling water and household Soda crystals.
 Plug oil holes in con rod with exhaust sealing putty.
 Coat a thin piece of string in exhaust putty, and place in bottom of side piece shoulders. This will prevent the liquid hot metal running out of the side of the cap/con rod during casting.
 Two tubs of heated white metal are required. One is the new metal to be used to pour the bearing. The other is old metal from previous jobs.
Place the con rod bearing end and big end cap  into the second tub and heat until the white metal is liquid. this will melt the old metal out of the con rod and cap and bring both upto casting temperature.
For the casting operation, place the assembled casting jig across the opened jaws of a bench vice. This will allow the big end cap to be positioned as shown in the photo's; and when the con rod is placed in the jig the length of the rod can pass down through the open vice jaws.
Pre-heat the jig and casting bar using a blow torch. This is important, because if the jig assembly is cold; the molten white metal will solidify in the jig before it has completely filled the jig.
Remove the cap from the second tub [pointed pliers]. the bearing surfaces can be scrapped clean with a piece of hack saw blade. Tin the surfaces with "Tinman's flux" and solder. Ensure surfaces are completely tinned.
 Place cap in the jig, position casting bar. Ladle out new white metal from first tub and pour into casting bar. If everything is hot enough, the hole in the casting bar will fill with molten white metal. at this stage let the whole thing cool, you will see the wight metal in the casting bar hole "go off". Cooling can be assisted with an airline directed at the assembly. When cool, a sharp tap with a light hammer on the end of the casting bar will free it from the cap/white metal.
Repeat the process for the con rod, and remaining con rod assemblies.
Use a small drill to clear the exhaust putty from the oil holes in the con rods.
 Remember this process produces LEAD FUMES, so good ventilation and a face mask are essential.
Likewise protective clothing and gloves.

[Colin Reed]

Some further info that has been emailed to me tonight:

“This thread started by Greig and added to by various people has landed at just the right time for me and has already answered some of my questions.
Attached are a couple of photos of the Con-rod re-metaling mould / jig I made.
This idea really started with some idle time in the workshop, a conversation and nothing else to do.
As can be seen from the photos it is basically in two parts.
The Base, this is a piece of Ground Stock Bar 9x1x3/8”there is a ½” diameter “Gudeon Pin” fitted to one end. The pin was reduced to 3/8” and screw-cut to BSP with an undercut at the shoulder. The bar was threaded to match with a light ½” counter-bore. I use a Tapping Attachment to ensure it is exactly square. Obviously a guide block or drilling machine could be used. The idea behind this was to use it as a check and make sure the con rod was not bent. By putting the cleaned rod onto the Pin and allowing the rod to lie against the base it can be easily seen if it is true and adjusted to suit before any further work.
The Mould, the main part of the Mould is made from Cast Iron. I used an old window weight for material. It is usually an open grain “dirty” material and they can be found at most joiners workshops. The idea for using Cast Iron is the Babbitt is less likely to stick to it. I made two 1 ¾” flanged pins 1- 3/16” diameter keeping the flange ¼” thick and milled them to the exact centre line. These were screwed to 2 mild steel plates 2-3/8 x 1-1/2 x 1/8”with the big end bolt holes accurately pitched. The main reason for making 2 parts and machining to the true centre line was to make it easier to find the centre of the big-end for machining ie not oval on assembly. Also both halves can be poured at once.
On assembly, before using my intention is to dust the Cast Pin with Graphite powder or rub over with a joiners pencil to prevent sticking. It will be seen that the base is not absolutely necessary when in use, but my thoughts were, it is a secure way of holding in the vice with a piece of insulation under the Cast pin to minimise heat loss.
I am working on a way to machine the sides of the con-rod after building the sides up. Obviously it must be central and true to the rod axis. I think we are almost there!
Now for a question, what flux to use for tinning my thought was Baker Fluid (Killed Spirits)
I hope the above ramble makes sense and may be of some use.
Tod”

Hi Ruairidh,
How are you planning to flow the metal around the sides for the side thrust,
I would use Tinning powder and no killed spirits, the powder is rubbed in with a wire brush                  

And once tinned dip in molten tin this gives an indication of how good the tinning has been done
Having a substantial jig helps keep the heat in it needs to be about 250 degrees C

Cheers Colin

[Ruairidh Dunford]

This is a problem we are yet to solve Colin - I will let Tod come back to you.

Thank you.

[Colin Reed]

This is a problem we are yet to solve Colin - I will let Tod come back to you.

Thank you.

Hi Ruairidh,

Will do a couple of sketches of how our set up was will probably have to e mail them for you to post for me, if that's OK
Colin

[Ruairidh Dunford]

That would be great - thank you Colin!

[Greig Smith]

Hello Chaps

Firstly thank you all for your valued input on this subject, I need to have the rods sorted in a short-ish space of time as I've offered the car to a friend to drive and the rods need to be sorted out rather urgently, so I'm now on a steep learning curve.....

The pictures of the jigs are invaluable, I too am curious about how to cast the white metal so as to get the thrust face on the side of the cap...... I've been considering how to do this and hold the rod in the dead centre, your collective jigs show this clearly, however I just can't see how the white metal will be able to 'cast' around the edges of the caps, hopefully the picture below will highlight this more clearly.

The rods are all that's stopping us from rebuilding the motor, we've bored out the oil pump and done the double oil jet conversion a-la Mike Forrest, so hopefully this shouldn't happen again. Quite a few of the tips and tricks in the 750 Bulletins from the '50's have been incorporated into this car and the supercharged sister car we're busy building...

Cheers
Greig

[Tod]

The mould / jig I have made is still work in progress, started through a conversation. My thoughts were to make a separate mandrel to protect the big end bearing and form the thrust sides by puddling after clamping the con rod and cap together, then machine the thrust sides using the big end bolts as a datum point. Having said that and done this work I think the mould that John has shown is proven to work and may well be the best option. How ever I enjoyed making it and reading all the valuable information posted on this thread,it is amazing the information out there.    Tod