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 Post subject: Ettore Bugatti design considerations
PostPosted: Sat Jul 04, 2009 2:18 pm 
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Location: Reeuwijk, The Netherlands
Let me first quote Lazarus:

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Goodwood 2009: Sadly the T73c blew its back axle due to the fact that we now have the power promised by Ettore ! 253 BHP at the wheels.[ 278 BHP at the flywheel ] Why on earth did Ettore fit what is essentially a Brescia back axle on such a potent car?


I have asked the same for many times.

I understood the T35 gearbox also basicly is a Brescia gearbox (bugwrench?). As engine output is increased dramatically, what does it to to the gearbox and bearings? I understand the gears were widened at some point. Then up to the type 51. An even more potent car. Same for type 59, which seemed to have suffered from gearbox problems.

Again the gearbox: The drawing for a recordcar with a type 41 engine, suggests installing a 5l gearbox (type 46). Would it be able to handle the power from an up-tuned type 41 engine (12.7 liters as opposed to 5 liter)

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One can turn things around as well:
With so many "generic" parts used on different types, would parts sometimes not be overweight and overrated for the job? In my previous life I have raced sailboats, and there the motto was: If it does not break, it is overweight.

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 Post subject: Re: Ettore Bugatti design considerations
PostPosted: Sat Jul 04, 2009 6:00 pm 
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Location: Vienne France
This rear axle does not look to be capable of transmitting more power than a T59


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 Post subject: Re: Ettore Bugatti design considerations
PostPosted: Sat Jul 04, 2009 6:18 pm 
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Location: Vienne France
There is some logic to slowly strengthening parts until they stop breaking.This is a sure way to make sure that the weight is kept to the minimum.The T35 gearbox is indeed based on the Brescia one.There was always so little information about the prototypes that we really do not know just how far they got with the development program.The big blower is a case in point.It worked well on the testbed but it seems that it was not tried on the car until Roland tried it at Molsheim in the early fifties.Then a special inlet manifold had to be made because nobody had realised that there was no space between the blower and the steering tie rod.The back axles broke consistantly on the T73 roadcar fitted with the T252 motor,even though they had maybe only 125 BHP to deal with.A new backaxle had to be designed,much like a T57 with a ribbed case.Obviously it is better to start a development such as this from where the factory left off,and all the T73c's today should have the big blower,later differential etc.Hugh Conway once told me that "this car needs a proper engineering based development program"Hopefully this is what we are now doing.Getting the engine right was clearly just the first step.


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 Post subject: Re: Ettore Bugatti design considerations
PostPosted: Sat Jul 04, 2009 7:20 pm 
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Joined: Thu Jun 26, 2008 5:17 pm
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My memory is a bit hazy but there was an article in "Bugantics" written by one of Ettore's senior draughtsman who maintained that the design of the transmission of the racing type 73 was faulty and certain components would not be adequate to trnasmit the projected power.

Having recently moved home I can't find my index to Bugantics but I think the editor of the magazine occasionally looks at this site and might be able to provide the reference.

I think the article was written over 25 years ago.


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