Author Topic: Bugatti Typ 50 1/4 Scale model  (Read 73522 times)

Offline Vixen

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #180 on: December 04, 2017, 01:54:25 PM »
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

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

Hello Michael

We had a conversation about the spark plug construction a while ago. It may be best only to use the JB Weld to bond the tungsten electrode into the macor insulation, I would make sure there is no JB Weld exposed between the two insulator parts, to prevent the risk of tracking between the central electrode and the outer body. Can the insulator be made as a single part?

Keep us posted about progress

Mike
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Offline michelko

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #181 on: December 06, 2017, 09:41:59 AM »
Hi Mike,
of Course it could be made from one Piece.
But macor is realy expensive, so i made only the part that is exposed to heat from that.
A fellow member of an other Forum gave me some crap pieces macor for free.
Trying to get the best out of that pieces.

Michael

Offline Vixen

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #182 on: December 06, 2017, 10:27:44 AM »
Hello Michael

I fully understand about the price of Macor, the cost is astronomic.
I am sure a one piece insulator will be better and should solve your ignition problems.
Try to make as many one piece insulators as possible from the free gift. Fortunately, some of your two piece insulators still work OK.

Good luck.

Regards

Mike
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Sometimes, it can be a long and winding road

Offline BillTodd

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #183 on: December 06, 2017, 05:49:19 PM »
where in the world are you micheal? might be able to supply a couple of bits of macor

Bill

Offline michelko

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #184 on: December 10, 2017, 08:48:54 PM »
Hi Bill,
many thanks for the kind offer. I live in germany.
If you have some pieces i would gladly take them.
Of course i will pay for the postage.

Regards Michael

Offline BillTodd

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #185 on: December 10, 2017, 09:18:29 PM »
I'll see what i can find in the scrap bin ;-)
how long are your plug insulators ?

Offline michelko

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #186 on: December 11, 2017, 11:13:26 AM »
Hi Bill,
the length is 44,5 , Diameter is 5mm.

Regards Michael

Offline BillTodd

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #187 on: December 11, 2017, 06:09:20 PM »
I've a couple of short lengths of bar stock (25mm diameter approx 70mm long) that you could probably quarter and turn , but I'll check at the works for something easier to work .

send me an address via pm (don't worry about postage)

Bill

Offline michelko

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #188 on: December 17, 2017, 03:57:16 PM »
Oh man this little stinker is driving me crazy.
A new problem encountered. If i remove the exhaust it runs realy good and stable without fouling the plugs.
Putting the exhaust on it stops running after 1 or 2 minutes with all plugs wet. :hammerbash:
Any body knows whats going on?
How did you guys setup the exhaust? Diameter, collector, etc.

Michael

Offline Admiral_dk

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #189 on: December 17, 2017, 05:15:49 PM »
I can not say that I have any experience in this size .... but if full size practise applies here too - your collector diameter and the following pipe is too small ...!

On a street bike with a "Four into One" - you place all four header pipes next to each other, so they fit into a square and the across size of the square is more or less the diameter of the following pipe. The header pipes are usual 5-10% bigger than the diameter of the channel in the cylinder head

So while your design in reply 155 looks fine, it's absolutely NOT a power exhaust system .... but a restrictor.

Best wishes

Per

Offline Vixen

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #190 on: December 17, 2017, 05:34:25 PM »
Hello Michael

I tend to agree with Admiral, Your exhaust system is probably acting as a restrictor.

That gives you a problem. The exhaust system you have built is true to scale size but an exhaust system to improve running will need to be much larger than true scale size.

It is difficult to advise how much bigger the pipes need to be. I would experiment by running the engine without the final tail pipes. Then try increasing the size of the tail pipe after the 4 into 1 joint to double the inside diameter of the four down pipes. That should help.

Later, you could try to make a new exhaust system out of very thin wall pipe to improve the flow but not spoil the scale appearance.

This is a difficult one.

Mike
« Last Edit: December 17, 2017, 05:38:59 PM by Vixen »
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Offline Tennessee Whiskey

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #191 on: December 17, 2017, 05:53:39 PM »
Is it a possibility that valve overlap and exhaust duration are at a borderline that will not tolerate any restrictions  :shrug:  Just thinking with my fingers.

Cletus

Offline michelko

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #192 on: December 17, 2017, 06:09:06 PM »
Sitting here in the livingroom before the fireplace i had some similar thoughts.
The header without the endpipe makes the same effect. I will open up the flange.
Another thought was the cam timing as cletus mentioned.
 What numbers do you guys run? Maybee there is to much overlap?
Not looking for max power, just stable run at the stand would be nice.

I think i will take the engine into the cellar, where it is not so cold as in the shop and do some adjustments.

So many variables to sort out :facepalm:

Michael

Offline Vixen

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #193 on: December 17, 2017, 06:26:06 PM »
Michael

Another variable is the fact that the full size Bugatti has a supercharger to blow the smoke out of the cylinder before adding the fresh charge.

I have looked at the exhaust system for my supercharged Mercedes W165. The exhaust pipes appear to have similar undersize proportions to your Bugatti and the same 4 into 1 arrangement. Both engines were designed in the same era, before gas flow was fully understood. Maybe the supercharger helpes clear the exhaust gasses.

I know for sure, the full size Mercedes W165 suffers badly from plug fouling, They must start with hot plugs but drive with cold plugs. If the driver stalls the engine, it fouls the plugs and they have to start all over again with the hot plugs. With the cold plugs fitted the driver needs to keep the engine revs constantly between 4000 and 8000, no slow tick over allowed.

You are not alone.

Mike
« Last Edit: December 17, 2017, 06:31:56 PM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Tennessee Whiskey

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #194 on: December 17, 2017, 06:46:04 PM »
I was just having a look through some rare restoration parts supplies for specs on the original camshaft and found out that the original was supercharged and popped back to say the same thing Vixen said while I was away. Have you tried seriously reducing the fuel and maybe even try a bit more spark advance.

Cletus

 

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