ERP
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| posted on 13/4/05 at 12:27 AM |
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They don't care about the weight because getting to 200+mph is all about aerodynamics. The weight in this application is for the most part
meaningless, it might cut down your 0-100 time by a fraction of a second, but it won't affext your top speed significantly.
When you worried about power to the ground vs a force which is proportional to velocity^3. It's all about the last 50 mph not the first..
Although I happen to agree with you the diff seems unnecessary in this application.
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Spyderman
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| posted on 13/4/05 at 11:57 AM |
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Not wishing to be arguementative, but would disagree quite strongly about the weight issue.
Whether acceleration rate is high or low the mass still has to be accelerated upto the intended speed. Forgetting aerodynamics for the moment, the
greater the mass of an object, the greater the power needed to achieve the same results, especially in terms of frictional losses. Simple physics!
In order to achieve new records you need to alter the balance in your favour. Here he is trying to beat the speed record for a certain engine class.
The only way to do that is to either have more power available or to have less weight (frictional losses being considered a constant to simplify)!
Both would be preferable! 
Still, the fact that it has encouraged debate is significant in itself! 
Terry
Spyderman
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andkilde
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| posted on 13/4/05 at 01:03 PM |
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quote:
Why use the wood if it is not to keep weight down? 
I'm pretty sure the wood is just a mockup Spyderman -- to be re-created in steel once he's got his design fully sorted.
Cheers, Ted
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chrisf
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| posted on 13/4/05 at 01:11 PM |
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Just to throw out another idea...Have you looked at ATV differentials from IRS ATVs? Knowing absoluetly nothing about them, perhaps they too are shaft
driven and spin in the oposite direction. They are certainly small. To the best of my knowledge, the only RWD Honda that I know id the S2k, and that
spins in the proper direction.
Maybe the CRV diff would work. I have a friend that had one and wrecked it. The insurance adjuster told hime that the CRV was very crumble prone, and
thus most frontal collisions netted in a total write-off. If you look, the CV joints and halfshafts may be ideal. Perhaps you can check with your
honda friends and see what they think.
I still think the chain drive is a better idea, but the ATV diff could be another possibility.
--Chris
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ERP
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| posted on 13/4/05 at 05:28 PM |
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quote:
Originally posted by Spyderman
Not wishing to be arguementative, but would disagree quite strongly about the weight issue.
Whether acceleration rate is high or low the mass still has to be accelerated upto the intended speed. Forgetting aerodynamics for the moment, the
greater the mass of an object, the greater the power needed to achieve the same results, especially in terms of frictional losses. Simple physics!
In order to achieve new records you need to alter the balance in your favour. Here he is trying to beat the speed record for a certain engine class.
The only way to do that is to either have more power available or to have less weight (frictional losses being considered a constant to simplify)!
Both would be preferable!
Still, the fact that it has encouraged debate is significant in itself!
Terry
OK assuming that the car is entirely aerodynamics limited i.e not limited by it's gearing, then we have
Fnet = Fdrive - K*velocity^3
ma = Fdrive - k*velocity^3
it's maximum speed is derived by solving
0 = Fdrive - k*velocity^3
Note, no mass in the equation. Now this is a gross simplification and does assume that you have an infinite amout of time and space to reach the
limit, in the real world it's more like
0 = (Fdrive - k*velocity^3)-(m*amin)
where amin is some small number where we aren't getting useful accelleration.
mass is a factor, but the Velocity^3 term is dominant, and the closer we get to our theoretical maximum the less important Mass is.
So yes mass matters, it dictates how quickly tou get to the point of diminishing returns, but it's not as important as say on a dragstrip car
where you are still accellerating at a significant rate at the end of the run.
[Edited on 13/4/05 by ERP]
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tigris
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| posted on 15/4/05 at 10:44 AM |
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strange question
how do you mount this type of diff? Is it just floating and supported by the axles? am I missing something?
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Rorty
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| posted on 15/4/05 at 12:56 PM |
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quote:
Originally posted by tigris
how do you mount this type of diff? Is it just floating and supported by the axles? am I missing something?
The diff is supported by bearings (in their original positions) which are clamped to the chassis or bulkhead.
 
Rescued attachment diff-machining_24.jpg
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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Rorty
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| posted on 15/4/05 at 12:59 PM |
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Here's another:
 
Rescued attachment diff_housing03.jpg
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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Rorty
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| posted on 15/4/05 at 01:02 PM |
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...and another:
 
Rescued attachment ZX12_trans.jpg
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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Rorty
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| posted on 15/4/05 at 01:07 PM |
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....wait....there's more:
 
Rescued attachment Saxon_rear_bulkhead.jpg
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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The Shootist
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 posted on 15/4/05 at 02:57 PM |
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The CRV doesn't have a rear diff...
The CRV uses on-demend awd. The rearend is a spool with the axles coupled via electric clutches. everything is disengaged under normal conditions but
when the ECU senses splippage in the front wheels the rear clutches engage and pushes the car untill slippage stops.
I've jumped on the wifes CRV pulling out of a side street only to have the rearend kick in and jerk the front of the car back over in a straight
line.
This is the same tried and true system that Honda has used since the Civic Wagon 4X4 in the 80's.
Now it may be possible to spring load the cluthes and turn the honda diff into an LSD, but that would be highly experimental.
It is a pretty tiny rearend though.
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kb58
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| posted on 15/4/05 at 03:29 PM |
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Rorty, that center diff assembly is really sweet... someone needs to sell them!
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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Rorty
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| posted on 15/4/05 at 10:21 PM |
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quote:
Originally posted by kb58
Rorty, that center diff assembly is really sweet... someone needs to sell them!
Funny you should say that. I've had machinists and fellow competitors standing around such completed assemblies, all oooh-ing and ahhhh-ing
stating it would be a crime against humanity not to put the units into production. But try and secure an order for one from anyone and all
you'll here is "I'll have one if the price's right, how much are they?"
"To you sir, they're $x,xxx, but if I can get some indication of commitment and numbers, then the price will be $x,xxx less $xxx"
In other words, it's the usual scenario where everyone wants one and nobody will buy one.
Perhaps if I had a degree in marketing I could sell them, but I don't. If I was brave enough, I'd just produce a run of, say, fifty of
them and then mark them up appropriately.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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Rorty
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| posted on 16/4/05 at 01:11 AM |
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quote:
Originally posted by The Shootist
The CRV uses on-demend awd. The rearend is a spool with the axles coupled via electric clutches. everything is disengaged under normal conditions but
when the ECU senses splippage in the front wheels the rear clutches engage and pushes the car untill slippage stops.
This is the same tried and true system that Honda has used since the Civic Wagon 4X4 in the 80's.
Does anyone have a workshop manual or any other material showing this diff in detail?
I've driven behind CRVs in the past, and always thought the diffs and axles looked very neat and tidy.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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CD-5
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| posted on 20/4/05 at 01:14 PM |
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Listing diffs possibility anyone?
Anyone tought about making a list of the potential donnor diffs, type and the car it is from? Ratio for non chain drive use...
Maybe some civic one for non lsd, subaru,etc...
Keping in mind the availability and cost.
I'm willing to put it in writing. Ithing it would be verry helpful for every one preparinfg a MID-BEC....
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