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PostPosted: November 30, 2013, 8:29 am 
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Ran into this while going through the The Motor Car. They had lifted it from the H.A.M.B. Definitly a different take on how to build a vehicle. Any thoughts about the wisdom of the basic layout?

http://www.jalopyjournal.com/forum/show ... p?t=200438

Bill


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PostPosted: November 30, 2013, 9:31 am 
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It's basic physics 101, you are causing the tail to swing around a fulcrum and once pendulum has been established there is nothing to counter it except for the friction of the rear tire.

Anyone who has "played" on a forklift will confirm this.

Corbin (Corbin Seats) almost put a single seat mini car into production, the Corbin Sparrow with this layout - not the later Myers car that was normal front steering.


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PostPosted: November 30, 2013, 9:46 am 
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Ditto the first part. Dangerous above walking speed for the only steering to be from the rear wheel.

The Corbin Sparrrow was put into production. Unfortunately, the government subsidy (I think it was $5000) only applied to cars, not trikes. I think that is why Corbin Motors went bankrupt, then was bought and renamed Myers. It is basically the same car, steering included. It uses a vw bug transaxle, kennedy electric motor adapter, flipped ring and pinion to turn the transaxle around, rabbit suspension and brakes, with 13 ultima batteries. There was also the corbin merlin that initially used a harley engine with plans for a watercooled v4 from Corbin, but Corbin Motors didn't get that far off the ground.


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PostPosted: November 30, 2013, 10:54 am 
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Miatav8,MstrASE,A&P,F wrote:

The Corbin Sparrrow was put into production.


The Corbin Raven was what I was thinking of and apparently the rear steering was supplementry to the front steering.


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PostPosted: November 30, 2013, 10:59 am 
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As someone who has driven a forklift, I agree that it doesn't seem like it should work at all. But there are a few crazy brits that actually built a very fast rear steer car, and it seems to have worked out quite well for them. ;)

Image

On a more relevant note, here's a video that talks about the old Mini they hacked up as a proof of concept (@ 07:36).


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PostPosted: November 30, 2013, 11:53 am 
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Miatav8,MstrASE,A&P,F wrote:
was also the corbin merlin that initially used a harley engine with plans for a watercooled v4 from Corbin, but Corbin Motors didn't get that far off the ground.



Any idea of what 4 speed transmission they used on the Merlin? I looked and I couldn't find any good shots of the engine transmission interface nor any articles that stated the transmission.

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PostPosted: November 30, 2013, 12:55 pm 
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Yeah, but can it parallel park? :D I'm sure the inputs at the wheel are large compared to a fraction of a degree rotation of the rear wheels. It would be interesting to know the turning radius of the mini compared to a normal mini. I still think it is going to be dangerous at one end of the operating range or the other, by design.

The transaxle is just a normal vw transaxle near as I can tell. I took a photo of a drawing by Corbin Motors of the sparrow at the microcar museum back in 2009. I'll have to locate that to share.

There is also a drawing off a reverse trike I found a few years ago with the same config but more like a motorcycle riding position. It was called a dragon fly or fire fly. I'll look for that too. It used bellcrank steering to a handle bar but otherwise the same.


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PostPosted: November 30, 2013, 9:45 pm 
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Wow, it took so long to load I forgot my question. I hope it's my connection and not the whole site.

Oh wait, I remember!

Wouldn't rear steer require bigger angles to get the same turning radius than a traditional front steer?

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PostPosted: November 30, 2013, 10:45 pm 
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Going back to the first post .....

All modern iceboats use a conventioanl front-steering tricycle configuration. Until the 1930's, all iceboats were rear steer. Whether front or rear steer made no difference to speed, all else being equal, but rear steer iceboats had an alarming tendency to do the equivalent of a tail-dragger aitplane's ground loop, which at 60 MPH or so could scatter the crew far and wide. Notwithstanding the apparent success of a rear-steer LSR car, I'm not sure I'd want to drive a rear steer car at highway speeds.

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PostPosted: December 1, 2013, 8:02 am 
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carguy123 wrote:
Wow, it took so long to load I forgot my question. I hope it's my connection and not the whole site.

Oh wait, I remember!

Wouldn't rear steer require bigger angles to get the same turning radius than a traditional front steer?


I'm not sure, but to steer left the wheel would need to turn right, so you turn left, it swings right, then goes left as it mentioned in the video. Tiny changes at speed would make for quick turns, similar to a little tow out on the rear alignment of a normal car (scary quick lane changes). Also because the front doesn't turn relative to the chassis at all, there would be significant front scrub. It is probably one of those things where you could get used to driving it, but the learning curve may bite you hard!


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PostPosted: December 1, 2013, 8:28 am 
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Found my pic on somebody elses site. :cheers:


You do not have the required permissions to view the files attached to this post.


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PostPosted: December 1, 2013, 12:31 pm 
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That pic shows an Audi 3 speed automatic and based upon the cylinders, the centerline of the engine crank appears to be above the centerline of the transmission.

But based upon the K&N air intake it appears to be in the proper spot.

But in either case it looks too clean so either they fudged on this drawing or they had some sort of casting made.

I have an almost new 111 S&S motor in a bike that I've been unable to sell so I keep toying with putting it in a car or trike. The power band looks almost like a Miata engine and the weight is negligible. The issue is mating it to some kind of transmission to get a reverse and a reliable clutch. I've even toyed with an automatic. So I keep looking at all applications of the engine. Now back to your regularly scheduled thread.

But one thing I know, IF I ever build it, it won't be a rear steer.

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PostPosted: December 1, 2013, 1:27 pm 
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carguy123 wrote:
Wouldn't rear steer require bigger angles to get the same turning radius than a traditional front steer?


Think of it this way: If you were turning into a parking space in your very conventional car but then stopped and put it into reverse without changing the position of the steering wheel, would you expect the car to go somewhere other than where it had just been?


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PostPosted: December 2, 2013, 7:35 pm 
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I've always read and agreed that rear steer is inherently unstable, but how about putting the steering axis-ground intersection in front of the contact patch so cornering force wants to straighten it out.

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PostPosted: December 2, 2013, 9:52 pm 
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Cornering force - i.e. sideloads - will tend to increase the desire for the rear steer wheels to increase lock as trail or caster increases on a rear steer chassis. Can't figure out why the same isn't true for front steer, except perhaps for good old slip angle. Use of caster for self-centering seems contrary to this.

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