gixermark
|
| posted on 4/10/07 at 09:50 AM |
|
|
Quaiffe ATb vs. plated diff
Hi Guys,
i have a live axled car - and need an LSD added for track work...
whats the consensus on ATB vs. plated diff ?? the ATB seems handy - in that no set up is required, and little/no minatenance...
Down side is they may have issues when/if a wheel is lifted off the ground - as it locks ?? therefore may be an issue when lifting going over
kerbs....
is the std half shafts in a english live axle 22 spline ?
Mark.
|
|
|
|
|
JimSpencer
|
| posted on 4/10/07 at 10:37 AM |
|
|
Hi
Asked this question myself a few years ago.
General consensus then was that the plated diff was too vicous in a light car like a seven and to go for the ATB
Did so and been very happy with it, totally sorted the inside wheel spining up, plus made the car more predictable if needing to slide around a
bit.
Not had any problems when kerb hopping either, but saying that I tend to find excesive use of agresive kerbs in a 'Seven' just throws the
car around too much anyway, so avoid them if they're really big 
|
|
|
kb58
|
| posted on 4/10/07 at 01:25 PM |
|
|
quote:
Originally posted by JimSpencer
General consensus then was that the plated diff was too vicous in a light car like a seven and to go for the ATB
I hadn't heard that, what do you mean by "vicous"?
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
|
|
|
kikiturbo
|
| posted on 4/10/07 at 01:39 PM |
|
|
maybe too much preload for a light car?
|
|
|
kikiturbo
|
| posted on 4/10/07 at 01:42 PM |
|
|
problem with the ATB diff and other Torsen type diffs, is that if you have one wheel off the ground or ona a very slippery surface, the diff becomes
in effect, open diff... as the worm gears in it work like torque multipliers... where as with a plated diff you still have limited slipp function..
that is why in racing people use mostly plated diffs..
other possibility is iscous diff, but in my experience, it takes some time to start working everytime you start sliding the car.. so I prefer the
torsen...
|
|
|
gixermark
|
| posted on 4/10/07 at 01:55 PM |
|
|
so.... are you saying that the ATB will be no advantage on a wet track say ??
I'm just trying to understand the pro's and con's before buying one...
will be >90% track use
|
|
|
ChrisGamlin
|
| posted on 4/10/07 at 05:17 PM |
|
|
I have Quaife ATB in my live axle'd car and its fine in the wet and dry. As mentioned the only time it would become ineffective is if the
inside wheel actually lifted, but in reality on a lightweight circuit car that doesn't particularly like riding kerbs anyway, how often does
that happen, and for how long? I could see it being an issue in a rally car where you're forever hanging wheels into gulleys etc, but on track
if you do hop a kerb and the rear wheel lifts, its only going to be off the ground for fractions of a second so the difference between having limited
drive and no drive in that fraction of a second is going to boil down to a tenth of bugger all
Lots of the RGB racers use ATBs, as you mentioned the big advantage is they work out of the box and dont need fettling all the time which is a big
bonus with an English axle on most cars as they aren't the easiest things to take in and out, so any milliseconds lost with a Quaife on the odd
corner would be more than counteracted with a plate diff that wasnt quite set up properly or had drifted out of its optimum setup, thus adversely
affecting the car's performance for the whole event.
Generally though, they're worth getting whatever you decide on. There's good demonstration of how an LSD helps the car hook up out of the
hairpin after Hall Bends at Cadwell here, without it mine used to spin the inside wheel to
oblivion, see some of the old Llandow clips as an example!
Chris
[Edited on 4/10/07 by ChrisGamlin]
|
|
|
gixermark
|
| posted on 4/10/07 at 08:40 PM |
|
|
cheers Chris..
so - did you just fit the ATB yourself ?? i assue there is a lot less to the install of at atb vs. setting the preload etc on a plated diff ?
any idea of rough lap time improvements you seen ?
Mark
|
|
|
kastrato
|
| posted on 5/10/07 at 02:29 AM |
|
|
Chris what radio diff are you using?
By the way I lost the card of the club again...
My wallet was been stolen again...
MK INDY fireblade
|
|
|
Bob C
|
| posted on 5/10/07 at 10:50 AM |
|
|
I put an ATB in my 3.14 7" sierra diff. You need to do a tiny bit of filing - there's a picture (or 2) in my website - to get it into the
casing.
On the road it behaves loverly - the only issue is that when you accelerate in a low gear (on the straight) you can feel it lock up - get a real kick
up the backside - I guess a viscous would be gentler. Otherwise you wouln't know it was there - exactly as it should be!
Bob
PS I assume it's diff locking that boots me up the chuff when I floor it in 1st & 2nd - no proof of this, just can't imagine what else
it would be!
http://freespace.virgin.net/bob.carter/locost_build.htm
bottom of page
[Edited on 5/10/07 by Bob C]
|
|
|
ChrisGamlin
|
| posted on 5/10/07 at 11:48 AM |
|
|
quote:
Originally posted by gixermark
cheers Chris..
so - did you just fit the ATB yourself ?? i assue there is a lot less to the install of at atb vs. setting the preload etc on a plated diff ?
any idea of rough lap time improvements you seen ?
Mark
Hi Mark
I didn't install it myself, you need to dismantle the CWP and put it in, it installs in place of the existing planetary gears, then the CWP
needs setting back up again with the right mesh (as you now know from the thread on the WSCC!). Once thats done though, its bolt-in and forget about
it.
Im not sure on laptime improvements as I only do trackdays and have only recently video'd my sessions (which along with data logging is the only
"legal" way you can time, doing it retrospectively), and since installing the diff Ive also upgraded the engine to an R1 and got better
dampers, but judging on cars I was following when I was at Cadwell a few years ago (WSCC racers who do ~1:41-1:42 laps) I think my car is currently
~2-3s a lap quicker round there than it was with the blade installed, and given the blade RGB class C record is only a second or so off the Class A
record (for Busas etc) at that circuit, I wouldnt say the engine makes up much of that.
Chris
|
|
|
ChrisGamlin
|
| posted on 5/10/07 at 11:50 AM |
|
|
quote:
Originally posted by kastrato
Chris what radio diff are you using?
By the way I lost the card of the club again...
My wallet was been stolen again...
I assume you meant ratio?
Mine's a 3.54 which is the highest (and most BEC suitable) you can get for an English axle.
As for the "club", I assume you're inadvertently aiming that at Chris Darby (zxrlocost), not me! 
|
|
|
kastrato
|
| posted on 5/10/07 at 12:04 PM |
|
|
oupppsss yes I mean ratio no radio! typographical error!
Yes I meant the bec owner club sorry for that too!
I am planning to change by diff ratio to something shorter cause the tracks in Greece are very small so I need maximun accelaration (the kit car is in
Greece you see)
I was thinking something like 3.92 or even smaller 4.44 etc
Do you think that this would work or is it going to be to short?
I am using the fireblade engine by the way and at the moment I am changing to 13" wheels for the same reason
(when I bought the car had 17' on.... just to look good I guess...)
MK INDY fireblade
|
|
|
gixermark
|
| posted on 5/10/07 at 12:17 PM |
|
|
thanks guys...
chris - yes... i think i was lucky with my 'diff rebuild' as per the threads on WSCC !! but now that i've done it - if i buy a ATB
unit i will probably do it myself - and just pay more attention to the mesh - and install a new crush washer this time :-)
Re: lap times - i feel like i am losing a lot of time on our local track... I am about 1-1.5 seconds of pole pace, i am reckoning the LSD will give me
at least 0.5-1 second a lap asbolute minimum - i can nearly count the time i'm losing exiting the chicane & hairpin.....
Bob - interested in your comment re: teh Diff 'locking' on hard acceleration in 1st and 2nd ?? can you elaborate ?
|
|
|
ChrisGamlin
|
| posted on 5/10/07 at 12:33 PM |
|
|
quote:
Originally posted by kastrato
I am planning to change by diff ratio to something shorter cause the tracks in Greece are very small so I need maximun accelaration (the kit car is in
Greece you see)
I was thinking something like 3.92 or even smaller 4.44 etc
Do you think that this would work or is it going to be to short?
If you're only going on those short circuits and never need to hit above ~110mph then a 3.9 might be OK, but a 4.4 would leave you on the
liimiter before 100mph Id think, which would be too short.
Having said that I changed from a 3.9 to a 3.5 with my blade engine'd car and 13" tyres and saw no significant increase in acceleration.
It felt quicker because you were changing gear more often, but in side by side comparisons to a mates Megablade it made no significant difference, so
if you ever drive it on the road or may occasionally go to a longer circuit and need higher top end, Id leave it as is.
cheers
Chris
|
|
|
Bob C
|
| posted on 5/10/07 at 12:33 PM |
|
|
What happens is that as I accelerate I get one or two sudden boosts in the acceleration. My initial thought was that the engine was coming on the cam
with a bang, but it happens more than once and feels like a boot up the backside - i.e. rather too surprising to be torque curve related. My theory
now is that one wheel starts to break traction and when the ATB 'notices' it instantaneously locks the diff - I don't know what else
could give such a sudden increase in acceleration?
I've not tried hard acceleration in a low gear while cornering yet ..... :^)
Bob
PS I must sort out my tyres so I have the same rubber on all corners - that might be an issue too.....
[Edited on 5/10/07 by Bob C]
|
|
|
ChrisGamlin
|
| posted on 5/10/07 at 12:53 PM |
|
|
Hi Bob
Seems odd, Ive certainly not noticed anything at all like that with my ATB on road or track so maybe there's a fault with yours? If there was a
significant amount of wheelspin though then you'd hear it clearly too as you can in my Llandow Youtube vids in the "bus-stop" part
of the circuit.
From what I understand though a correctly working ATB doesn't "react" to wheelspin inso much that the instant one wheel is going
minutely faster than the other (even if its turning a corner with no wheelspin), the diff has a certain amount of effect. This is way before any
significant spinning of one wheel could occur, its not like traction control that senses wheelspin then reacts to it, so I suspect the cause may lie
elsewhere.
cheers
Chris
|
|
|
Bob C
|
| posted on 5/10/07 at 03:31 PM |
|
|
Sorry about the possible thread hijack here.... but I really can't think what else might be going on!
Re. how the ATB works - the clutch & viscous LSDs try to limit the speed difference between wheels and therefore must convert the difference into
heat. The ATB doesn't have energy absorbing surfaces & they claim no wear happens so it must be a locker rather than a slipper!!! They
specify a ratio at which it locks - I assume this must be a torque ratio, it's set by the face angle on some of the internal gears but I forget
all the details.
I think it actually uses magic......
Bob
|
|
|
ChrisGamlin
|
| posted on 5/10/07 at 07:51 PM |
|
|
They specify a ratio which is the maximum amount of torque it can apply to one wheel compared to the other, its not a ratio where it locks AFAIK,
because (according to their blurb anyway) it doesnt ever fully lock.
All that means is that if there's sod all grip (and therefore torque capacity) on one wheel, it can't give 99% to the other wheel which is
its known weakness dicussed above.
cheers
Chris
|
|
|
gixermark
|
| posted on 6/10/07 at 06:13 PM |
|
|
hi chris - what is the 'known disadvantage' of the atb unit ???
it seems they may not be a s good on lsippery surfaces which could be a concern when racing in the wet... ?
|
|
|
ChrisGamlin
|
| posted on 6/10/07 at 11:21 PM |
|
|
Hi Mark
The known disadvantage is as mentioned above, if one wheel lifts, the one on the ground loses drive.
Ive not heard of or experienced any adverse issues with it in wet conditions though, if anything I think it would be better in the wet than a plate
diff in certain circumstances because it doesn't really induce any turn-in understeer unlike a plate diff, and IME with a car like ours in the
wet (even with an open diff), understeer is more often than not the biggest hurdle to overcome to generate good pace, rather than rear end grip.
cheers
Chris
[Edited on 6/10/07 by ChrisGamlin]
|
|
|
gixermark
|
| posted on 7/10/07 at 10:27 AM |
|
|
ok- so worst case is if i do actually lift a wheel over a kerb ar whatever,it will basically be like hitting the rev limiter for that split second -
as the other wheel has no drive either..
i guess the only other thing is that it may add a bit of load on the drivtrain when the wheel is back down - but with low torque figures of a bec it
shouldn't be a big deal...
Thanks again
|
|
|
