Bugatti Typ 50 1/4 Scale model

[Vixen]

Michael,

Looks good.
How is the tungsten electrode fixed in the macor insulator. and how will the macor insulator be fixed in the plug body?

Mike

[michelko]

Hi Mike,
here is a cut drawing of the plug. I will silversolder the tungsten electrode to a short piece of m2 thread.
This is to screw on the conector and to hold the setup in the isolator.
The smal gap between lower and upper isolator part is filled with jb weld which also hold and seal the electrode.
The idolater itself will be hold by small crimped seam at the top of the metal body.

Michael

[Vixen]

Hello Michael,
The choice of JB weld is good. JB weld appears to have a much higher temperature resistance than most epoxy resins.
The tungsten electrode looks to be about 1.5 mm diameter.

Mike

[Vixen]

Michael,

I just checked the data sheets for JB Weld. The data sheets show it contains both steel and carbon black particles. I could not find any information about the insulation (conductivity) properties of the material. I would be cautious when using JB Weld to make spark plugs.

It may be OK to bond the tungsten electrode into the macor insulation, but make sure there is no JB Weld exposed at the ends. You can wipe off any excess with acetone. I think you should ensure there is absoluty no JB Weld between the central electrode and the earthed outer body. otherwise there is the risk of tracking when the high spark voltage is applied.

Mike

[michelko]

Mike i had the same concerns, but they write on their Homepage jb weld is an Isolator  https://www.jbweld.com/pages/faqs

So i gave it a try on my first set of plugs. There was no Problem withe the jb weld but with the corian that was eaten away by the sparks.

Nevertheless i will Keep the jbWeld in the smal chamber between the the two Isolator parts. Just to be sure.

Michael

[michelko]

April 2016
Conrods are complete machined. Only Needs some sanding to break the Corners.
Startet on the pisons. They are also made of 7075.

Used a bore gauge to messue the cylinders. I made the Pistons with  a 0,03mm undersize.

[michelko]

May 2016
Assembled the rods and Pistons into the block. Unfortunatly i had to correct the pisons because the valves hit the pison in some positions. So i machined some pockets into the Piston head. Will Show These pics later)
Also worked on the Valvetrain.
I machined the valvels from ETG100. Made the tappets and the shims.

[michelko]

June 2016
To form the valve seats i used this Handy tool. Ist a countersungk with a hole in it that i bought ready. I only had to bild a small pin that fittet to the hole and the other side to the valve guide

[michelko]

July 2016,
to make the lat cuts on the valves i made a quick and dirty holder.
The valve stem and the bottom where turned to spec.
 I also hardened the cams.

[michelko]

Another Job was to mill the side plates and engrave the Bugatti sign.

Last two pics Showing my machines.

[fumopuc]

Mike i had the same concerns, but they write on their Homepage jb weld is an Isolator  https://www.jbweld.com/pages/faqs

So i gave it a try on my first set of plugs. There was no Problem withe the jb weld but with the corian that was eaten away by the sparks.

Nevertheless i will Keep the jbWeld in the smal chamber between the the two Isolator parts. Just to be sure.

Michael

Hi Michael,
I have made the experience, that during powder coating, JB weld will not attract the powder if negative is conected to the part.
To overcome the problem, some iron powder was given on the soft surface and after curing the powder coating was no problem anymore.

[Vixen]

Michael,
Interesting comment from fumopuc that JB Weld is not conductive. However, I think you are wise to ensure the JB Weld does not bridge the gap between the center electrode and the earthed body. Very high voltages will always find a weakness in insulation.

Regarding your bronze valve seat inserts. How are these sealed into the cylinder head? Do you use a compression joint or do you bond (glue) the inserts to prevent gas leakage. Another use for JB Weld perhaps?

Mike

[michelko]

Mike,
As always i am a little anxious, so i used loctite 648 and a press fit.

Michael

[Vixen]

Michael
Loctite 648 is the higher temperature retainer so should be OK. Luckily the Bugatti is water cooled and so the cylinder head temperature are controlled.

Following along with every move you make and learning all the time.

Mike

[michelko]

Hi Guys,
here is a short update on the new set of plugs.
Isolator from macor ready, Body from steel ready (only hex missing).
Upper part of Isolator to make.