Author Topic: Bugatti Typ 50 1/4 Scale model  (Read 36006 times)

Offline cwelkie

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #255 on: April 16, 2018, 01:46:06 PM »
Excellent progress Michael - even with the odd miss, your engine sounds wonderful.
Keep at it, you'll get all the little things sorted out.
Charlie

Online michelko

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #256 on: April 16, 2018, 01:50:16 PM »
I am thinking of making oil rings out of leaded free turning steel. What do you think?
my first oilrings where made out of cast iron and i was not able to assemble them onto the piston they al broke at the oil return slit.

Can steel be annealed like the cast iron? Or do i have to make them bigger in Diameter?
Is brass useable?

Any thoughts or comments from the specialists are appreciated

Thanks Michael

Online Jo

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #257 on: April 16, 2018, 03:32:37 PM »
Eric and I just discussed this and we agree that you are going to struggle to get the annealing/springing right - even in full sized vehicles they normally use CI rings. A few fancy engines use high spec steel chromed steel rings  ::)

CI rings will outlast you  ;)

Jo
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Offline Stuart

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #258 on: April 16, 2018, 04:27:08 PM »
In my long dim past my dad did up a Ford 8 (old sit up and beg ) car

The oil control rings were in multiple parts thin steel rings two in the grove they had a wave type spring steel backing and a further ring like a dished washer again spring steel , so four parts to the ring in the grove

Stuart
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Online Vixen

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #259 on: April 16, 2018, 06:02:31 PM »
What were the dimensions (diameter, width, height, slots etc) of the cast iron rings that would not stretch and broke?

Mike
It is the journey that matters, not the destination

Online Jo

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #260 on: April 16, 2018, 06:48:43 PM »
The oil control rings were in multiple parts thin steel rings two in the grove they had a wave type spring steel backing and a further ring like a dished washer again spring steel , so four parts to the ring in the grove

Yes Eric mentioned in our discussion that a backing wavey spring is required to get the pressure right  :facepalm:

Jo
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Offline Zephyrin

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #261 on: April 16, 2018, 09:05:57 PM »
As regard brass, I don't know, but phosphor bronze is suitable for piston rings, very tough material, very springy.
In my hands, cast iron rings break when they are more thick than high.
may be the profile created in yours rings introduces a lot of stiffness, hard to see how a thermal treatment would amend that

Online michelko

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #262 on: April 18, 2018, 12:59:01 PM »
Hi,
the first set of rings where 1,6 mm high and 0,8mm deep with a groove with ~0,6mm.
The holes are 1 mm. When i read These numbers i blieve the Diameter of the hole is to big. Maybee also to much holes?
The rings i tryed to assemble broke through the hole.

Instead of the holes i might try to slitt the ring at  4 positions and left the side oposed to the gap unmachined.

Michael

Online Jo

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #263 on: April 18, 2018, 01:21:38 PM »
The hole is HUGE relatively :o of course it will break. Try something nearer 0.3mm

Jo
Usus est optimum magister

Online michelko

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #264 on: April 18, 2018, 01:28:44 PM »
yes i will, are there any benefits of using slits against holes?

Michael

Online Jo

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #265 on: April 18, 2018, 01:43:28 PM »
Slits spread the force load when you stretch the rings... you will probably get away with a slightly wider slitting saw..

Try it and we will see  :D

Jo
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Online Vixen

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #266 on: April 18, 2018, 02:28:15 PM »
I agree with Jo, those 1mm holes are far too big and would be major stress concentration points. The rest of the control ring dimensions look reasonable.
Smaller drain holes would be better, several thin slots would be even better. It would be best to keep the slots as thin as possible.
You should also consider missing out the hole or slot on the opposite side to the ring gap, where the bending forces are highest when you fit the rings to the piston.

Mike

It is the journey that matters, not the destination

Offline Craig DeShong

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #267 on: April 20, 2018, 01:22:43 AM »
I use a slitting saw.  I think these were done with a .020 inch saw.  I had no problems installing the oil ring.
Craig

Online michelko

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #268 on: April 20, 2018, 10:27:43 AM »
Craig These look like my new design. I just ordered a small slitting saw blade 25x0,5mm.

Will make then a new set of  rings. Just hate the idea to disassemble the hole engine to fit them :Mad:

Michael

Offline Admiral_dk

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Re: Bugatti Typ 50 1/4 Scale model
« Reply #269 on: May 07, 2018, 09:04:19 PM »
Hi Michael

On a 8 cylinder inline you shouldn't get any positive pressure in the crankcase if the pistons + rings seal perfectly ....
As this never happens in real life, you will need a vent (or more).

My first four-stroke engine was a Suzuki GS550 (inline four) and it had a 12mm hose from the cylinder head to the airbox. This was enough in standard trim, but when power was increased it blew big amounts of oil out that way - despite a reasonable labyrinth in the head - so I had a collector box with a connection back to the crankcase => problem solved.

I'm just trying to tell you that you certainly need to have a good breather from the crankcase, but even then you still might have a problem that requires the oil control rings too ....

On a vey different note - I saw a running Bugatti Type 35 51 from 1933 at the local race track yesterday. A beauty and nice sounding for the first two laps - the driver then gave it quite a bit more pedal and it started to cuff sputter and misfire and one and a half lap later it wasn't running on all eight anymore  :'(

Another guy was running an Alfa Romeo 308 formula one car from 1938 much slower, but he kept going to the end.

Best wishes

Per
« Last Edit: May 07, 2018, 09:14:07 PM by Admiral_dk »