LocostUSA.com

Learning how to build Lotus Seven replicas...together!
It is currently Mon Sep 01, 2014 3:32 am

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 288 posts ]  Go to page Previous  1 ... 10, 11, 12, 13, 14, 15, 16 ... 20  Next
Author Message
 Post subject: Re: AWD Locost?
PostPosted: Thu Nov 10, 2011 9:58 am 
Offline
User avatar

Joined: Sun Sep 10, 2006 11:29 pm
Posts: 378
cheapracer wrote:
I've posted this in 3 different threads now but the info is indeed relevant to all 3 ...

I have mentioned a few times that one solution is to turn the V8 around, run a 4WD box forward and run a driveshaft back to a rear diff and forward to a front diff if you want 4WD, well here is one very successful lo(w)cost example ...

So watch these ..


The issue with doing this on a budget is that you will be using OEM parts. And AFAIK there is no OEM center diff that can be turned around to give rear bias. Your choices are either run a front bias system or a locked system. And if you run a locked system, then your f-r brake bias is negated and every time you pull the handbrake all four tires lock up.


Top
 Profile  
 
 Post subject: Re: AWD Locost?
PostPosted: Thu Nov 10, 2011 1:24 pm 
Offline
User avatar

Joined: Wed Nov 09, 2011 5:46 pm
Posts: 23
Location: Europe
if good understant cheapracer, similar to skyline r36 (not trasfer box in rear, but all gearbox)
Image

ford rs200 in rear engine
Image
subaru libero rear engine
Image

gearbox from audi,
Image
http://auto-lib.ru/?p=334

_________________
Never be afraid to do what you dont learn, remember: amateurs built the ark - Professionals built the Titanic.


Top
 Profile  
 
 Post subject: Re: AWD Locost?
PostPosted: Fri Nov 11, 2011 2:59 pm 
Offline
User avatar

Joined: Wed Nov 12, 2008 6:29 am
Posts: 3359
modernbeat wrote:
The issue with doing this on a budget is that you will be using OEM parts. And AFAIK there is no OEM center diff that can be turned around to give rear bias.
Your choices are either run a front bias system or a locked system.


Lamborghini simply run a vicious LSD to the front diff on all their AWD's (and VW do it on the way to their rear diffs) - you don't actually need a center diff.

I hypothesize that an overrunning sprag clutch with a shorter front diff ratio would do it to but have never tried it - but DP Cars is about to so will see how that turns out for them (front drive freewheels unless wheel'spinning rears catch up).

Anyway, bottom line is I would prefer a powerful car with 4WD than 2WD if can't have AWD.

modernbeat wrote:
And if you run a locked system, then your f-r brake bias is negated and every time you pull the handbrake all four tires lock up.


Nope, but you need individual handbrakes to lock up the outside rear only - you forgot cars have diffs.


Top
 Profile  
 
 Post subject: Re: AWD Locost?
PostPosted: Sat Nov 12, 2011 1:27 am 
Offline
User avatar

Joined: Sun Sep 10, 2006 11:29 pm
Posts: 378
cheapracer wrote:

modernbeat wrote:
And if you run a locked system, then your f-r brake bias is negated and every time you pull the handbrake all four tires lock up.


Nope, but you need individual handbrakes to lock up the outside rear only - you forgot cars have diffs.


I'm speaking from experience here. I built and crew a Subaru rally car with a welded center diff. The handbrake locks up all four wheels. The rears through the brakes and the fronts through the drivetrain.


Top
 Profile  
 
 Post subject: Re: AWD Locost?
PostPosted: Sat Nov 12, 2011 1:37 am 
Offline
User avatar

Joined: Mon Apr 12, 2010 5:40 pm
Posts: 1831
Location: san francisco bay area
cheapracer wrote:
Lamborghini simply run a vicious LSD to the front diff on all their AWD's (and VW do it on the way to their rear diffs) - you don't actually need a center diff.


Honda did something similiar with the RAV4. .. a FWD vehicle with a locked transfer case and a viscous coupler on the rear diff pinion shaft.
If the front tires (and therefore the driveshaft) get going faster than the pinion shaft it starts to engage and power the rear wheels. You could use the same concept in the front.
Sure would be a lot easier to fit if you tilted the engine.

_________________
"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett


Top
 Profile  
 
 Post subject: Re: AWD Locost?
PostPosted: Sat Nov 12, 2011 3:55 am 
Offline
User avatar

Joined: Wed Nov 09, 2011 5:46 pm
Posts: 23
Location: Europe
Had the idea to viscous coupling. Use honda pasport (usa model if good remember, 4x4 offroad vehicle) gearbox. Gearbox have front/rear 0/100% front/rear, or 50/50% center lock. Center lock is bad on hard surface, so on the front driveshaft put viscous coupling. When they want to have fun can use RWD or 4WD :lol:

_________________
Never be afraid to do what you dont learn, remember: amateurs built the ark - Professionals built the Titanic.


Top
 Profile  
 
 Post subject: Re: AWD Locost?
PostPosted: Sat Nov 12, 2011 1:08 pm 
Offline
User avatar

Joined: Mon Apr 12, 2010 5:40 pm
Posts: 1831
Location: san francisco bay area
Honda Passport = Isuzu Rodeo. Badge engineering. ..

_________________
"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett


Top
 Profile  
 
 Post subject: Re: AWD Locost?
PostPosted: Sun Nov 13, 2011 10:34 am 
Offline
User avatar

Joined: Wed Nov 12, 2008 6:29 am
Posts: 3359
modernbeat wrote:
cheapracer wrote:


Nope, but you need individual handbrakes to lock up the outside rear only


I'm speaking from experience here. I built and crew a Subaru rally car with a welded center diff. The handbrake locks up all four wheels. The rears through the brakes and the fronts through the drivetrain.


Read my post again.


Top
 Profile  
 
 Post subject: Re: AWD Locost?
PostPosted: Sun Nov 13, 2011 10:50 am 
Offline
User avatar

Joined: Wed Nov 12, 2008 6:29 am
Posts: 3359
This is a typical Lamborghini front diff, the viscous coupling is in that bulge (red arrow) - easy hey, so off you go to the local car wreckers, should be plenty laying around for surely no more than $100 ....


Attachments:
lambo diff.gif
lambo diff.gif [ 8.86 KiB | Viewed 2143 times ]
Top
 Profile  
 
 Post subject: Re: AWD Locost?
PostPosted: Sun Nov 13, 2011 2:08 pm 
Offline
User avatar

Joined: Wed Nov 09, 2011 5:46 pm
Posts: 23
Location: Europe
cheapracer wrote:
This is a typical Lamborghini front diff, the viscous coupling is in that bulge (red arrow) - easy hey, so off you go to the local car wreckers, should be plenty laying around for surely no more than $100 (250 Lt) ....


but need two, one stock, one remove viscous coupling (same diff ratio front and rear)

_________________
Never be afraid to do what you dont learn, remember: amateurs built the ark - Professionals built the Titanic.


Top
 Profile  
 
 Post subject: Re: AWD Locost?
PostPosted: Tue Nov 15, 2011 1:59 am 
Offline
User avatar

Joined: Wed Nov 12, 2008 6:29 am
Posts: 3359
frezi wrote:

but need .. same diff ratio front and rear


Close enough would be fine I think preferably with a slightly shorter rear ratio. I don't know how far apart the ratios could be before heat in the viscous coupling constantly slipping starts to be an issue.

But a bit irrelevant in a 'lo(w)cost' arena anyway.


Top
 Profile  
 
 Post subject: Re: AWD Locost?
PostPosted: Tue Nov 15, 2011 7:41 am 
Offline
User avatar

Joined: Wed Mar 30, 2011 7:18 am
Posts: 457
Location: central Arkansas
cheapracer wrote:
I hypothesize that an overrunning sprag clutch with a shorter front diff ratio would do it to but have never tried it - but DP Cars is about to so will see how that turns out for them (front drive freewheels unless wheel'spinning rears catch up).


I'll be watching too. I've thought much the same thing.

My guess is that under some circumstances there'd be a noticeable thump as the sprag locked. There might also be some odd steering wheel twitches when rocking the throttle in a corner. The OEMs want to avoid customer complaints but it would be no problem for me.

Quote:
Anyway, bottom line is I would prefer a powerful car with 4WD than 2WD if can't have AWD.


I don't even require "powerful" to any large degree. The closer you push a 2wd car to the edge of the traction circle, the more it closely resembles a ballistic missile than a guided vehicle. 4wd lets you change the car's yaw angle and apply power whether it's steering or sliding; the edge of the circle changes from a sharp limit to a fuzzy range where you can do things a 2wd driver can only gawk at. More power just lets you do it at lower speeds.

"That car looks like a cat on a slippery floor when it makes a turn..."


Top
 Profile  
 
 Post subject: Re: AWD Locost?
PostPosted: Tue Nov 15, 2011 1:23 pm 
Offline
User avatar

Joined: Mon Apr 12, 2010 5:40 pm
Posts: 1831
Location: san francisco bay area
I'm sure ya'll remember the 4wd spitfire pic's I posted. ..
Here's a little something for your entertainment along similiar lines. (little :shock: :rofl:)

http://www.youtube.com/watch?NR=1&v=MDU5BU_qSJU

_________________
"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett


Top
 Profile  
 
 Post subject: Re: AWD Locost?
PostPosted: Thu Jan 05, 2012 9:14 pm 
Offline

Joined: Mon Dec 19, 2005 9:29 pm
Posts: 68
cheapracer wrote:
I have mentioned a few times that one solution is to turn the V8 around, run a 4WD box forward and run a driveshaft back to a rear diff and forward to a front diff if you want 4WD, well here is one very successful lo(w)cost example ...



I have a question about this setup. In a standard inline front engine layout the prop shaft to the rear diff turns clockwise facing it from the front of the car, does the prop shaft to the front diff turn clockwise as well? If so if one was to use the layout listed above the drive shaft would now rotate counterclockwise facing from the front of the car, correct? If one was to swap the diffs, that is put what would normally be the front diff to the rear, which rotates counterclockwise in it's normal orientation when facing from the prop shaft input, and rear to the front, which would now be rotating counterclockwise when facing it from the front of the car but would also be turning clockwise when facing from prop shaft input, it's normal direction, wouldn't the need to turn both diffs upside down no longer be necessary to get the proper wheel rotation?
This is confusing and a bit of a brain teaser for me without having a diff in front of me to figure it all out and if one would end up with "more forward gears than reverse"


Top
 Profile  
 
 Post subject: Re: AWD Locost?
PostPosted: Thu Jan 05, 2012 10:06 pm 
Offline
User avatar

Joined: Mon Apr 12, 2010 5:40 pm
Posts: 1831
Location: san francisco bay area
Ummmm, hmmm. :?
The easiest visualization I can think of is to imagine just the pinion and ring gear interaction (I use my hands).

Viewed from the front of the vehicle (front engine rear drive).
shaft outputs are all clockwise, the pinion is on the left side of the ring gear in the rear.
Since the diff is rotated on the horizontal plane (left axle becomes right axle etc) to fit in the front, the pinion is now on the right side of the ring gear and the shaft rotation matches up to the desired axle rotation.

So, if you reverse the output of the shafts by rotating the engine on the same horizontal plane then you would have to reverse the output of each diff to match.

Simplest way to do that is to flip the diff, most diff cases are assymetrical so you can't just flip the gears inside the case.
The problem becomes oiling since the ring gear is now throwing oil at the bottom of the pinion instead of the top where it can dribble down into the pinion bearing. ..

_________________
"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 288 posts ]  Go to page Previous  1 ... 10, 11, 12, 13, 14, 15, 16 ... 20  Next

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: Bing [Bot] and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
POWERED_BY