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Author Topic: New Vintage Project, 250cc M-VG, Reconstruction of a 1933 French Jonghi 350  (Read 25946 times)

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Offline manta22

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Patrick;

I wonder if this would keep the lead weights in place:

1. Clean the ID of each hole.
2. brush flux on the ID of each hole.
3. Cast the weights with 63/37 solder.

The solder should create a bond with the crank counterweights if the counterweight can be brought up to the melting point of this alloy, 361F.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline thefrenchowl

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I like your thinking, Neil,  :-D

I'll have a go, but the tinning of the the inner walls might bond with pure lead anyway?

Patrick
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Offline Ron Gibson

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I think the pure lead is way softer and will have a tendency to distort or flow more even if it is bonded to the holes. You can take a stick of 70/30 body lead and hang half of it over an edge. In time it will bend completely down under it's own weight.

Ron
Life is an abrasive. Whether you get ground away or polished to a shine depends on what you are made of.

Offline manta22

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I like your thinking, Neil,  :-D

I'll have a go, but the tinning of the the inner walls might bond with pure lead anyway?

Patrick

Patrick;

The reason I suggested using a 63/37 solder alloy is that it has the lowest melting point of any solder. Easier on your crankshaft.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline thefrenchowl

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Thank you both, Neil, Ron, for the advise...

This is the lead I have, roofing lead...



I bought a roll some years back when I repaired some of my roof that had a few broken tiles...

Would that be pure lead? It's very soft and easy to fashion...

The roll was round when I bought it!!!

Now collapsed under its own weight!!!

Patrick
« Last Edit: June 16, 2018, 03:50:23 AM by thefrenchowl »
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Offline bones

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Hi Patrick
  Re the lead weights in the crank. Can you get hold of some "mallory metal" and turn the weights.
 then press the pieces into the crank holes.They won't go anywhere. It's a carbide based metal that is machinable.

Also with the big end. If you have to replace the big end pin it would be a good idea to get rid of the crowded roller
setup. You should be able to find a caged big end bearing , with a silver plated cage preferably.

   cheers    Bones

 

Offline thefrenchowl

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Whaooo, we're getting somewhere!!!

Never heard before about this mallory alloy, that's what I love about this forum, lots of guys with slightly different perspectives and backgrounds, so plenty of proper advise given...

This is what I found about densities:

Iron: 7.87

Lead: 11.35

Mallory alloy: from 17 to 18.5

I did my 1st Jonghi 3 years ago with lead, despite not liking one bit the shape of the slugs that came out of it...

On this one, the slugs were moving about quite a bit but their weight is pretty consistant within 5 grammes which tells me none of it departed towards the bottom of the crankcases.

So I have a good reference for the weight to be added, rather than just fill the holes flush.



The big end and ancillaries are perfect, I'll leave them as is at this stage.

Just a bit of work, filing and polishing, to clean up the rod...

I also have a full set of NOS replacements, rod race, pin, nuts, rollers in a jar full of oil...  :-D





Thanks again!!! Well appreciated!!!

Patrick
« Last Edit: June 17, 2018, 05:19:39 AM by thefrenchowl »
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Offline thefrenchowl

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Busy weekend ,

I'll leave the crank alone while I investigate this Mallory alloy....

So, instead, I started the second petrol tank cap... It went better than I thought it would... (sommat bad bound to happen soon...)















In them days, these english caps came with four different levers, the flat one as shown, the basculing lever as on Sarolea Gregoire "monotube", the Brough Superior version with three balls and the Jonghi one with just one ball.

Today, only the flat lever is available...

I'll do the Jonghi version later, much classier!!!



So long,

Patrick
« Last Edit: June 17, 2018, 12:40:07 PM by thefrenchowl »
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Offline ggl205

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Never heard before about this mallory alloy, that's what I love about this forum, lots of guys with slightly different perspectives and backgrounds, so plenty of proper advise given

Mallory metal (also known by several other names) is just a tungsten alloy used for balancing cranks. Easy to tack weld too.

John

Offline manta22

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Never heard before about this mallory alloy, that's what I love about this forum, lots of guys with slightly different perspectives and backgrounds, so plenty of proper advise given

Mallory metal (also known by several other names) is just a tungsten alloy used for balancing cranks. Easy to tack weld too.

John

Expensive too!

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline thefrenchowl

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I'll see the costs when I find a supplier!!!

I finished yesterday by taking off the knee grips steel holders.

They'll be reused later once the tank extension is done. Plus a few rubbers to insulate the tank from the insane power of this engine  :-D







So long,

Patrick
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Offline wobblywalrus

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Patrick, you can heat the crank in a kitchen oven to around 450 degrees F.  Then, pour the lead in the holes.  The crank will cool and contract around the lead and this will help to hold it in place.

Offline manta22

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WW;

If he uses a flux, the lead will be soldered onto the crank. No shrink-fit is needed but it will help.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline thefrenchowl

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Hi,

I could do a lot of things with lead, but thinking about it, that's all they had as heavy metal in the 30s...

The std street Jonghi side valve was given for 4500 rpm...

The carb, cams and overlap of TT 2 should see its revs rise to well over 6000rpm, a 33% increase and centrigugal force rises at the square of the rpm.

Loads more strain...

I know the Jonghi racers had a different crank arrangement, but no photos or drawings have been found so far.

So, faced with using the street crank, I fancy improving it a touch!!!

Thanks again to all for the to and fro, it helps narrowing down the solutions.

See ya all,

Patrick

 
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Offline thefrenchowl

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Bit more done this afternoon after work: Air vent fitting for the tank...







Patrick
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