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Picture of Denny Trimble
Posted
Well, it's not quite working out...
http://students.washington.edu/dennyt/fsae/floating_sprocket.avi

Man, our car just about fell apart today, on our first drive since SVSU. We also discovered a broken front swaybar, which explains our handling at SVSU a little bit Smile

I guess we'll have some work to do this week before the Northwest FSAE Shootout!


Alumni, University of Washington
Structural / Mechanical Engineer, Blue Origin
 
Posts: 1215 | Location: Seattle, WA, USA | Registered: December 03, 2002Reply With QuoteEdit or Delete MessageReport This Post
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Wow, we were just talking about whether those heavily machined sprockets failed very often.

Replacing a sprocket and sway bar? It isn't like you had to pull the motor to fix your exhaust valves. Roll Eyes

Have any other teams confirmed their appearance next weekend?


Josh Gillett
Oregon State FSAE '04-'06
 
Posts: 343 | Location: Everett, Washington | Registered: August 25, 2003Reply With QuoteEdit or Delete MessageReport This Post
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Picture of Denny Trimble
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Well, this one is a little puzzling, given that we've run the same sprocket for 100 hours on a previous car before it cracked. We then made the replacement thicker, and this new one thicker, but it failed after less than 20 hours. We haven't determined what caused this one to fail so early yet. It could be our new guy used a program for a larger sprocket, or that we somehow received a sprocket blank that wasn't 7075.

Mostly I'm whining because we're in summer mode, and hope to do only about one day a week of work Smile

As far as I know, UW and OSU are the only confirmed teams for the NWFS. WWU and UBC are still tentative.

Today we also worked on making sure the parking lot was decorated properly in advance:



Alumni, University of Washington
Structural / Mechanical Engineer, Blue Origin
 
Posts: 1215 | Location: Seattle, WA, USA | Registered: December 03, 2002Reply With QuoteEdit or Delete MessageReport This Post
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Picture of rjwoods77
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Hey Denny,

Sorry for asking this but what is the point of doing that. Wont it increase chain slap on sprocket teeth? Looks cool but I was just wondering about the performance gain of doing that.


-I might be stupid but I got retard strength
-"I hate Rob Woods" tee shirts are now for sale
-I know the strippers real name.
-Because eggs is eggs
 
Posts: 855 | Location: Rochester NY | Registered: September 10, 2004Reply With QuoteEdit or Delete MessageReport This Post
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Picture of Denny Trimble
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It was a joke, our sprocket self-destructed today. It used to be one piece, now it's five plus five teeth missing (found one).


Alumni, University of Washington
Structural / Mechanical Engineer, Blue Origin
 
Posts: 1215 | Location: Seattle, WA, USA | Registered: December 03, 2002Reply With QuoteEdit or Delete MessageReport This Post
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Picture of rjwoods77
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Oh. I was gunna say.


-I might be stupid but I got retard strength
-"I hate Rob Woods" tee shirts are now for sale
-I know the strippers real name.
-Because eggs is eggs
 
Posts: 855 | Location: Rochester NY | Registered: September 10, 2004Reply With QuoteEdit or Delete MessageReport This Post
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Denny,

Maybe the problem was the 7075, It typically has low fracture toughness, any surface or material imperfections will result in a "pre-cracked" condition leading to early fatigue failure.

buddy


no signature necessary
 
Posts: 21 | Location: Arlington | Registered: April 05, 2005Reply With QuoteEdit or Delete MessageReport This Post
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On a similar note, we've destructed a rear brake disc 2 days ago. It will make a nice clock. I should post a picture sometime.


Didier Beaudoin
École Polytechnique de Montréal 2005-2008
École nationale d'aérotechnique 2004
 
Posts: 169 | Location: Montreal, Qc | Registered: December 02, 2002Reply With QuoteEdit or Delete MessageReport This Post
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Picture of Jersey Tom
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I agree with Buddy. 7475 might be a better option.



Colorado FSAE Alum | 05, 06, 07 (C-Cpt)
 
Posts: 888 | Location: Boulder, CO | Registered: March 31, 2005Reply With QuoteEdit or Delete MessageReport This Post
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nice lookin sprocket!

we have run 7075 rear sprockets for the last 2 years, last years car did student plus a load of testing, then went over to aus and competed over there, we necer had a problem with it, however, that was annodised (admitadly it didnt do much testing, but still a good 100/ 150 hours!)

this years car has a hard annodised sprocket, that has dome a lot of testing and student! (although we spapped a new chain in enduro Frown but that car is going to aus this year.

do you annodise your sprocket at all?? or maybe thought about leaving a little more material there!??


Rob.C - UBRacing2006
 
Posts: 48 | Location: Birmingham, UK | Registered: July 12, 2005Reply With QuoteEdit or Delete MessageReport This Post
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