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PostPosted: July 27, 2006, 1:34 am 
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I thought it was time I started a log of my build......
I started with a CMC frame, and am using a Toyota Celica rear axle, miata front spindles.

I used 3M VHB adhesive tape for the aluminum floor - a permanent tape used in various applications. Pretty strong stuff.....
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Even though the floor totally held my weight with just tape alone, I chickened out and added a few rivets just for good measure

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The engine I am using is a Yamaha FJR1300, a sports tourer bike engine, with 150HP and 99ft/lbs torque. It is closely related to the R1 engine

The engine is a shaft-drive, which has pro's and con's. It is already setup for a driveshaft, but unfortunately spins the wrong way.
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To cure the direction problem, I am mounting the rear axle upside down. This is an earlier mockup
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Looking inside the 3rd member, it looks like there will be oiling problems at the pinion bearing, so I am going to use this small electric pump
to pump oil around in a circle, keeping the pinion lubricated. I hope it will work
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I built a paddle shifter which seems to work nicely, although time will tell when it comes to actually driving it
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I found an aluminum radiator on ebay which really weighs about nothing...
It is from a Civic. It is a tight squeeze under the nosecone, but fits OK

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Coming from Ireland, I travel home from time to time. I was able to bring back a set of aluminum Protech shocks, and a pair of Triton fibreglass seats wwith me on the plane. (Wrapped up the seats and told them they were a baby's car seat!)
I struggled with my headers a couple of weeks ago, but finally got them finished. They didn't work out exactly equal length, but good enough for me....
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I have also been working on a solid model in work when I haven't been busy. I was able to beg, borrow and steal some components to save time, but has taken so many hours - I should have put them into the car instead!! I might be finished already
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I need to clock up more hours in the garage though, to get it finished. Since starting, I got a ride in a Hayabusa engined westfield, and a Hayabusa engined MK Indy, both local here in San Diego. What a rush! It's little things like this that really give you motivation!

Rob

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PostPosted: July 27, 2006, 11:05 am 
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Location: Concord, NC
Looking good there Rob! Good to see another BEC build going on over here (it was getting lonley :D ). Can't wait to see more progress...

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PostPosted: July 27, 2006, 1:55 pm 
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robertwa wrote:
I thought it was time I started a log of my build......
I started with a CMC frame, and am using a Toyota Celica rear axle, miata front spindles. Rob


Hi Rob, good to see you here. I need to stop by and check out your car, just as soon as this darn heat lets up.

Did you use Solidworks for CAD?

Kurt

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PostPosted: July 27, 2006, 3:09 pm 
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Hi Kurt,
I used One Space Designer, because I use it in work. It was originally bult by our company before it spun-off on its own. It is not a parametric history-based application like Solidworks, but rather is dynamic modelling.
Still though, files can be interchanged through IGES and STEP file formats.

Come down to visit anytime, but be sure to bring the Mini 8)

Rob

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PostPosted: July 29, 2006, 3:31 pm 
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Great build ya got going there. Very nice chassis, almost makes me want to order one instead of building it. Can't wait to see the finished product. Are the A-arms from CMC also?


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PostPosted: July 31, 2006, 2:23 pm 
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Quote:
Great build ya got going there. Very nice chassis, almost makes me want to order one instead of building it. Can't wait to see the finished product. Are the A-arms from CMC also?


Buying the chassis certainly saved me some time, although I had to chop and change quite a few tubes to suit my application, and on many an occasion wished I had built my own from scratch. I also replaced the steel floor for an aluminum one, since I am trying to go as light as possible for the bike engined build. The 'universal chassis' fro CMC really was nothing more than a 'book chassis'. The CMC Miata chassis would have been a much better purchase in hindsight.
The A-arms are from CMC, but will need modifying as I seem to have way too much positive camber.

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PostPosted: July 31, 2006, 8:03 pm 
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nice build really coming along. buying a chassis seems to shorten build time if alot doesnt need to be changed to fit the build. what width are the and how much are you actually saving by using AL.

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PostPosted: August 1, 2006, 9:48 am 
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To cure the direction problem, I am mounting the rear axle upside down. This is an earlier mockup


You may find that to be a problem. If you get a whine outta the diff, it's because the helical gears weren't meant to run backwards at high speed.

$.02


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PostPosted: August 1, 2006, 10:41 am 
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PaulG wrote:
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To cure the direction problem, I am mounting the rear axle upside down. This is an earlier mockup


You may find that to be a problem. If you get a whine outta the diff, it's because the helical gears weren't meant to run backwards at high speed.

$.02
Are they cut in such a manner that makes backwards rotation any different than foreward? I understand the the pressure/stress etc. will be put on the other side of the gear's "teeth" but unless the shape is different on these "backsides" of the teeth I don't see why it will function different. I'm not saying you are wrong, I just don't understand what makes you right. :lol:


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PostPosted: August 1, 2006, 11:04 am 
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Location: Corning NY
Chetcpo

In the automotive world, you typically use Spirial bevel gears or Hypoid. Hypoid being used if the pinion centerline is not on center with the ring gear. That and it is stronger but much more expencive. These gears have a "swirl" to them. They are stronger in one direction than the other (forward to reverse). A spiral and hypoid generaly engage 3 teeth as a straight cut gear only engages one tooth. In Spiral and Hypoid the front of the gear is a "cup" and the back of the gear is a "buldge" I could try to explaine it more but i think that pictures would be easer :)

I would NOT flip the rearend in a "racing" application. Its not safe, for the rear end to see that much torque.

Straight cut gear
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Spiral Bevel
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Hypoid Gear
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I don't know why my images are not working just copy and paste the links to see the pictures.

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PostPosted: August 1, 2006, 11:31 am 
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isomswim

Aluminum is ~60% lighter than steel given the same size and thickness. Now generally you would thicken up the aluminum to use in the floor of the car but it is still much lighter.

steel under the seat
46' x 32" x .035" = 14.5 lbs

Aluminum
46" x 32" x .06" = 8.6lbs

So it is 2x thicker it is still 1/2 the weight. So it is a good idea to use Aluminum over steel.

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PostPosted: August 1, 2006, 4:09 pm 
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Good discussions on the flipped axle. Believe me I spent a lot of time pondering and asking the same questions.
The two issues are oiling and strength. I think I have the oiling part sorted with my electric pump. As for strength, if you compare the weight of the donor car vs my finished weight (sub 1000 lbs hopefully), and the lower torque of the bike engine, I cannot imagine it being an issue.
Instead of the flat faces of the teeth engaging, the sloped faces will mate. The difference in strength will be the cosine of the tooth taper angle which corresponds to roughly 30% weaker, or the equivalent of using a smaller ring gear. Another issue is that the gears will tend to be pushed apart a bit, which will probably mean that its longevity will suffer. As for this, I am not planning on driving 100K miles, and if I need to change out a 3rd member every few years it is not so bad.
Another thing to bear in mind is that some 4x4's actually use the same ring and pinion in the front as in the back

I did look at alternative options, and still am, for peace of mind if nothing else. One option was to reverse the output of the engine by moving the driven gear in the middle gear assembly as in the picture below. Unfortunately there was not enough room to do it easily:
Image


Another option was to use a reverse gearbox inline on the driveshaft, and operate it in reverse the whole time in order to go forwards. However most boxes I have seen are not able of carrying large loads in reverse.

The best option I believe is to use a front differential from a 4 wheel drive vehicle, however I haven't seen a light enough one which has suitable gear ratios. I'll keep looking, as I may upgrade in the future.

Comments or any alternative options always welcome


KENLUDE97
Thanks for the calculation on the floor. There is of course also the 'bling' factor and the fact that the diamond plate doesn't 'drum' as much as a steel floor. But weight of course is the main reason.

Rob

Rob

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PostPosted: August 1, 2006, 4:26 pm 
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No problem on the Calcs....

I'm drawing a 442 right now in Pro-Engineer. And the weight calcs are as simple as 3 clicks. No real "work". The program is allready written.


If you need any other calcs let me know :D

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PostPosted: August 1, 2006, 6:25 pm 
A couple of points. The floor pan material should probably depend on the intended use. If the car is to be 100% a race car NEVER to be used on the street then aluminum would be the logical choice since you would be looking at absolute minimum weight. If the car is to see ANY street duty the few lbs gained is offset by the added safety factor, I wand something more substantial between my butt and the street than foil.

In a 4x4 the front shaft runs opposite to the rear shaft therefore the gears are turning the "correct" direction. FWIW my DD back awhile was a mid engined Corvair with the 400 hp engine in the location of the back seat and the transaxle turned around backwards. The transaxle had 60k on it at the time of the conversion and broke after another 60k on it. It broke because the end bearing on the mainshaft of the trans froze and snapped the end section, approx .125 wall. The repair was another used mainshaft, a bearing, and s syncro set for 1 gear which had kinda held everything in place. There was never a problem with the hypoid gears even though they were driven backwards and had approx 4x the original hp.


Last edited by locostv8 on August 2, 2006, 3:02 am, edited 1 time in total.

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PostPosted: August 1, 2006, 7:21 pm 
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stv8 is right it would work. I just would not reccomend it. EXCEPIALLY in a racing application.

I also asked this same question to a group of Mechanical Engineers that i work with and they all reccomended aginst it. And when i mentioned racing they went :shock: I can get the #'s from them on how much weaker they typically are in reverse. But just beware using stickey tires and high torque launches.

Straight bevel gears were used in the "old" auto differentials. And that would have been perfectly acceptable. If that is the case.

Good luck and build a good car 8)

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