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This Is Why I Love These 16 Valve Engines


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#46 pogie

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Posted 13 August 2017 - 06:14 AM

Exactly.

 

You cannot compare a F1 engine to a mini crank, or a top fuel dragster.

 

F1 cars have mega budgets for one, and there strokes are tiny  about 50 mm. they also have a bearing after every rod.

And will use the very very best in steel.

 

A top fuel dragster is only on full throttle for 30 seconds about 3 runs before a full rebuild then the crank is scrap, also these cars only go up the gears they dont come down the box which is where the crank is wanting to flex.

 

Cnc is used to save costs on one offs and in mass produced items, as its quick and relatively simple, if cost and time wasnt an issue forging would be used every time, but tooling costs are high its dirty dangerous work and you need large spaces for the process.

 

Out of interest, my father in law got talking to a guy he met on holiday whose son worked for Williams in the 3-1/2 litre V10 era.  The FIL is an engineer by trade and was interested in the engines and was told the Renault units would arrive in a crate and would be bolted up to the car and taken away again for rebuild once their hours were up and the Williams guys never got a look inside.  That was until a particular test where one of the engines grenaded itself and split the block so the Williams guys had a look inside and found the stroke to be about 28mm with a 125mm(ish) bore!



#47 Moke Spider

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Posted 13 August 2017 - 08:56 AM

I missed these;-

 

  Billet Cranks are used in Top Fuel Dragsters,

 

 

Exactly.

 

You cannot compare a F1 engine to a mini crank, or a top fuel dragster.

 

A top fuel dragster is only on full throttle for 30 seconds about 3 runs before a full rebuild then the crank is scrap, also these cars only go up the gears they dont come down the box which is where the crank is wanting to flex.

 

I don't know a lot about F1 stuff, so I'm not going there.

 

I also don't know a lot about Drag Cars, but a little.

 

Miglicars is quite right.

 

A Drag Car Engine only needs to survive less than 2000 revs, not 2000 RPM, but 2000 revolutions.Some story boards from a show I was in a few years back;-

 

65wipO2.jpg

 

xv73ANx.jpg

 

rTE1kkc.jpg

 

 

where their claim is that it only need survive 900 revolutions.I'll go out on a limb here and say that it's quite likely that these cranks will survive quite OK without a damper, not doubt too, the bottom ends are tuned such that critical resonance is no where near their running speeds.

 

By comparison, a few years back, I worked out that the crank in our Minis does around 1.5 million (1 500 000) revolutions for every 1000 miles driven. And they last how long (usually)?



#48 Orange-Phantom

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Posted 14 August 2017 - 09:34 PM

Some good posts on here.

 

When I was commenting on Billet cranks being used in F1 etc I was making the point of that they can hardly be terrible if they are used in the very top tiers of motorsport!

 

Moke makes some very good points on the subject and from my own research there really isn't any consensus in the industry as to which is better, the following statements from these crank manufactures highlights this....

 

Tom Lieb Of Scat:
“A forging is not as strong as billet because the forging process stretches and shears the grain structure. A forging starts out as round bar of metal and gets twisted and turned to make the rod throws. What used to be centerline of the bar is now offset, and the grains get stretched, traumatized, and weakened, although some sections of it are substantially stronger than in a casting. With billet, there are no stress riser areas because the grain structure runs parallel to the length of the entire crank. Forgings are stronger than billet in bolts and axles because the metal isn’t being stretched and sheared. There isn’t a single Top Fuel, Funny Car, Nextel Cup, or F1 team that uses forged cranks, so you have to ask yourself why.”

 

Dwayne Boes Of Callies
“If the exact same material is used for both, a forging is stronger than billet because the grain flow is upset and relocated. However, it’s much easier to get special alloys in a billet material.”

 

Judson Massingill Of The SAM:
“Up to 600 to 700 hp, forgings are every bit as good as billet cranks, given adequate journal overlap. However, when you start reducing the overlap with long strokes and small rod journals to reduce bearing speed, billet comes out on top. In our motors, billet lets us get away with less journal overlap.”

 

With regard to crank dampers I cannot find anywhere any reference that the viscous type was designed for constant high rpm use.  When I was enquiring to Kad about their Viscous type that stated it would be suitable for a road or race car.  When I explained my spec of car and what it will be used for (fast road) they stated it would be ideal.  Also to quote Fluidampr "Superior engine protection, broad range performance and durability are why you will find a viscous damper as original equipment in high quality sports cars and diesel trucks, such as the V10 equipped Audi R8 & Lamborghini Gallardo, and the Ram 6.7L Cummins".

 

Furthermore the elastomer dampers are tuned to damp a specific frequency, when rotating assembly parts such as the pistons, rods, flywheel or crankshaft are changed, this will cause a change in the assembly’s resonate frequency and may negate the effectiveness of the damper during peak torsional vibration altogether.  So a "one size fits all" elastomer damper may not be as effective as first thought.

 

Whereas with a Viscous Damper, To quote KAD "Due to the way the silicon fluid operates, it is able to tune itself to any instance of torsional vibration which may develop. Thus the engine will run smoothly and power impulses work in phase with the crank rotation and not against it. Engine bearings will last longer, cam drives run quieter. The engine gains from increased performance and greater reliability."

 

A viscous damper will effectively control destructive torsional vibration through the entire RPM range of the engine, not just a specific range. Viscous dampers aren’t tuned for a specific narrow band frequency. Because the inertia ring can freely rotate through the housing, it isn’t limited by the elasticity of the rubber.

 

http://www.kentautod...1-tooth-pattern

 

http://www.dieselarm...onic-balancers/

 

http://www.enginelab...spills-details/

 

Fluidampr showing HP gains here.

 

http://www.fluidampr...vr6-engine-106/

http://www.fluidampr...plications-104/

http://www.fluidampr..._HondaS2000.pdf


Edited by Orange-Phantom, 14 August 2017 - 09:38 PM.


#49 Moke Spider

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Posted 16 August 2017 - 09:21 AM

Some good info and food for thought there Orange man.

 

Apologies if I implied that Billet Cranks are 'weak' or not up to the task - of course they are and the difference between these and forged items - especially in our cars - is really quite academic.

 

In regards to Rubber (elastomer) mounter Dampers, yes, they are generally 'tuned' for particular frequencies and can't cover a whole range, They do need to be carefully selected for the particular engine characteristics. They are also not particularly stable with temperature nor over their life.

 

Fluid Dampers, while I don't have vast experience with them, they are not all made equal and also need to be selected with great care.

 

<Edit: I did particularly like this gif as it does show what's going on to a crank

 

IUbUCp4.gif   >

 


Edited by Moke Spider, 16 August 2017 - 09:24 AM.


#50 mini13

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Posted 16 August 2017 - 11:46 AM

Im like how the three crank experts cant even agree! LOL

 

 

thats a good gif, and does show the stresses where the crank normally gives issues.

 

AFAIK strength and fatige strength can be two very different things.



#51 Orange-Phantom

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Posted 16 August 2017 - 05:55 PM

Apologies if I implied that Billet Cranks are 'weak' or not up to the task - of course they are and the difference between these and forged items - especially in our cars - is really quite academic.

 

Fluid Dampers, while I don't have vast experience with them, they are not all made equal and also need to be selected with great care.

 

<Edit: I did particularly like this gif as it does show what's going on to a crank

 

 

 

No Apology needed!  All I was trying to get out there was Billet is a good option and as demonstrated by the Three Crank experts, there really does not seem to be any consensus, or at least in these examples.  You made some very good points about certain metals being available in Billet and not forged etc. It's always good getting another persons point of view.  It's how we all gain a better understanding and knowledge on our hobby.  :-)

 

The only Fluid Damper that I am aware of for the A Series Mini is the one made by KAD and I spoke to them about my spec and use.  I got one of these Dampers so that I could better protect the bottom end of my engine when I (and my brother) were rebuilding it.  The rubber was cracking on the old one!

 

 

Im like how the three crank experts cant even agree! LOL

 

 

thats a good gif, and does show the stresses where the crank normally gives issues.

 

AFAIK strength and fatige strength can be two very different things.

 

Yeah it did make me chuckle on how they all have different opinions!

 

The Gif is excellent.  Sometimes a visual representation is much better than trying to explain in words!



#52 Moke Spider

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Posted 16 August 2017 - 06:40 PM

AFAIK strength and fatige strength can be two very different things.

 

Agree with that 100%.

 

Material properties don't just come down to '"how strong is it mate?"

 

Hardness also has comes in to this and how different materials rate in terms of strength, fatigue resistance, elasticity etc.

 

 

Orange man, I think we're on the same page with that.

 

I'm certainly no expert with this stuff, but I have an idea what's going on and the problems it can cause.

 

As they say, a picture tells a 1 000 words and I think that gif shows the issue better that could be explained with 10 000 words.

 

 

Just coming back to Mini Crankshafts for a moment, if you look at those that have broken, they nearly always go in the same place, regardless of what crank the engine is for, and that's in the web between the centre main and no. 2 crankpin, which if you think about it and look at the crank assy, with a flywheel, it does become somewhat obvious that it's going to be a weak spot,


Edited by Moke Spider, 16 August 2017 - 06:46 PM.





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