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Old 01-06-2014, 01:39 PM   #342 (permalink)
CFECO
CFECO
 
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Join Date: May 2008
Location: Vail, AZ.
Posts: 552

X-Car - '11 Homemade 2+2

Velbly1 - '17 Toyota Camery XSE
90 day: 29 mpg (US)

Velbly2 - '13 Toyota Tundra
90 day: 18.03 mpg (US)
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Quote:
Originally Posted by visionary View Post
Reply to Godscountry

The weight is higher than I had hoped for, but there are a multitude of reasons. The frame is built from 20x20mm box section mild steel because it approximates the flat-plane design and the section width that a production based composite monocoque would be made from. My initial material order was for 1.5mm wall thickness, but in a later order I allowed 3.0mm to be delivered. This was an error with two consequences, firstly the lighter material was used in the structural construction thus making it less than ideal. Secondly, the heavier material was used to make the less demanding upper sections with a weight penalty and no strength benefit.
However, I still feel that this is only responsible for about 30% of the over target weight. Most is due to the complexity of the design and equipment that I have chosen, and maybe I should just accept that I was too optimistic from the start. Either way, I have now started to focus on the mass of components and have taken steps to reduce weight where it can be easily achieved.

Iíve added a photo of the side braces now that I have taken a plasma cutter to them, its removed a significant amount of weight but I cannot do anything about the box section weight without re-making them from scratch.




As for driving, the extra weight will undoubtedly hurt acceleration but thatís not a major concern. The main purpose of this vehicle is to prove the point about the possibility of doing 100km on 1litre of fuel at 100kmh average speed, from 100cc displacement, outside of that goal Iím not much concerned with poor acceleration. The critical factor in this test will be aerodynamic performance and thatís where I will concentrate my efforts.

Iím already working on a 250cc single cylinder engine version, which will make for a much more usable daily driver. The extra mass will impact much less on an engine with 30hp and a six speed transmission, making it a much more enjoyable vehicle to drive, still not quick but OK, I hope.
The tubing sections could get holes bored in them with a hole saw, not sure how you'd get the pieces out, and it would be a nasty job.
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