Twin Spark Engines

Alfa Romeo ONLY please!
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Mats
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Post by Mats » Fri Dec 16, 2005 9:49 am

Never in a 75 block.
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Post by Maurizio » Sat Dec 17, 2005 12:46 am

the 75 ts has no oil spray nozzles.
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Post by kterkkila » Sun Jan 15, 2006 1:26 am

I've been thinking using aluminium in front flywheel, but after all decided to go with RST. Here's some pics:

Image

Image

The flywheel itself (with starter gear) weights 1.6 kilos and complete assy with original center triangle is 2.7 kg. Could make it still a bit lighter, there is lot of safety margin left..

What about crankshaft? Do you see any negative aspects in sharpening counterweights? How much metal could been taken away without disturbing durability? Taking them completely away may not be good idea, though..
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Post by TS_turbo » Sun Jan 15, 2006 4:40 am

:shock: serios light flywheel is that i likie it ... what kind of steel is that?
SS or crome moly ? and what is overal thicknes of komplete wheel+cast triangle ... its must be the same as original cast wheel thicknes ... iam too curous about crank lightening ..there is alot of meat to remove, if i rememeber corect -1 kg of rotating mas(flywheel crank counterweights) is similar to -20 kg of dead weight in acceleration ...
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Post by Mats » Sun Jan 15, 2006 5:15 am

Nice! :D

Looks like you made it out a sheet of steel? You can get a LOT more weight off if you could ditch the std cast iron centre. :)
The gain in rotational mass is HUGE! Very interesting.
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Post by kterkkila » Sun Jan 15, 2006 7:35 am

Yes, it's made from stainless steel sheet. Not sure about the specific ASTM code. It was quite tough when turning in lathe, as SS's usually are.

Overall thickness is now 1.5mm more than in original flywheel, but that's near enough. Could compensate it by milling some material away, but guess won't bother..

The cast iron centre weights 1.1 kg. Could be lighter tough. Fortunately the mass is on small radius and won't do too much for inertia.
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Post by Mats » Sun Jan 15, 2006 11:36 am

kterkkila wrote:Yes, it's made from stainless steel sheet. Not sure about the specific ASTM code. It was quite tough when turning in lathe, as SS's usually are.

Overall thickness is now 1.5mm more than in original flywheel, but that's near enough. Could compensate it by milling some material away, but guess won't bother..

The cast iron centre weights 1.1 kg. Could be lighter tough. Fortunately the mass is on small radius and won't do too much for inertia.
If you think stainless is tough, try titanium. :shock: :D
Are you going to fix the centre to the flywheel somehow? Might be a bit of a problem, balance wise, if you don't.
Mats Strandberg
-Scuderia Rosso- Now burned to the ground...
-onemanracing.com-
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GTV 2000 -77 - Died in the fire.
155 V6 Sport -96 - Sold!
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Post by Maurizio » Sun Jan 15, 2006 11:44 am

Nice done, I'm not that keen on the original cast iron.
You might consider doing the center also in ss.
And leave then material in the places you really need it the triangle between the thee bolts.

Saluti,
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Post by kterkkila » Sun Jan 15, 2006 12:34 pm

I'm not going to fix parts together, but will mark them to keep them in same position after balancing.

I think I'm done with the front wheel for this time. May think SS center triangle later. Now must concentrate on other things, like rear flywheel. There's still some work to do ;)

Image

Should the crankshaft been knife edged like this Opel crank? Suggestions?

http://homepage.ntlworld.com/david.jack ... rt_eng.htm
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Post by kterkkila » Sun Jan 15, 2006 12:54 pm

Great example.. That Opel engine was ruined soon due to broken crankshaft :shock:

http://homepage.ntlworld.com/david.jack ... _build.htm
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Post by kterkkila » Sun Jan 15, 2006 2:35 pm

Have anybody been weighting 155's crank? Is there smaller counterweights than in 75's? Pics??
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Post by Mats » Sun Jan 15, 2006 2:53 pm

kterkkila wrote:Great example.. That Opel engine was ruined soon due to broken crankshaft :shock:

http://homepage.ntlworld.com/david.jack ... _build.htm
Jumping to conclusions are we? :)
How do you know it wasn't from the fact that the block was bores alot and it cracked then snapped the crank? :wink:
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-Scuderia Rosso- Now burned to the ground...
-onemanracing.com-
-Strandberg.photography-

GTV 2000 -77 - Died in the fire.
155 V6 Sport -96 - Sold!
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Post by kterkkila » Sun Jan 15, 2006 11:41 pm

Mats wrote: Jumping to conclusions are we? :)
How do you know it wasn't from the fact that the block was bores alot and it cracked then snapped the crank? :wink:
Thats true, can't say which failure started the explosion. I guess the most serious mistake was to start hassling with Opels :lol:
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Post by MD » Mon Jan 16, 2006 12:32 am

kterkkila

I like the way you're thinking and then having the balls to go out and just do it. Love it ! That's the good bit.

My conservative side suggests that you may develop your own broken crankshaft with such a light flywheel. The reason I say that is that "other" job of the flywheel is to absorb some of the vibrations and do some form of dampening itself . If there is not enough mass there, the crankshaft will have to do a lot more itself. The question is, can it take it?

I guess you'll just have to suck it and see .

I do agree with other comments that you may need to better integrate the two components and balance it as a unit before mounting onto the crank. I think it would be a safer and better option with better balancing outcomes.

Having said all that poobah, there is only one other thing to say, oh wow !

Keep us updated.

BTW. Opel, is that like a German Skoda ? :D
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Post by Mats » Mon Jan 16, 2006 4:57 am

It's not like he is going to drive it 30 000Km a year with it... :)
Mats Strandberg
-Scuderia Rosso- Now burned to the ground...
-onemanracing.com-
-Strandberg.photography-

GTV 2000 -77 - Died in the fire.
155 V6 Sport -96 - Sold!
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