72 replies to this topic

[Heath]

What parts of a Banjo do you think give them such a bad reputation? And what actually gives way?

I'm interested because I've heard people very briefly talk about putting bigger diff components into Banjos, and now I can kinda imagine it after working with them a little.

The fact that they only have two pinion gears probably makes the standard centres a bit limiting. I've never blown one up before but I gather they often shear the pin or strip the teeth off the planetary gears?

Heat is probably a pretty significant problem with such a small diff, particularly if you're doing standstills, but you can always run thicker oil or use a diff cooler in more extreme cases

Has anyone here ever made up a set of axles for their car? What material? Can you weld a flange onto the axle and then machine it? or does it have to start off as one piece of billet?

In a very extreme case, if you were to make up a full spool and even more-so willing to look at using a different type of wheel bearing (something with the same O.D. and bigger I.D.), you could probably upsize the splines and the whole axles. There isn't that much to limit you then. How strong do you reckon it could be? Still using the standard 3rd member, diff housing, pinion, crown wheel, bearings etc, just put a decent crush tube on the pinion for good measure.

I know, I know... "why would you bother"

[Heath]

Did some very basic calculations and it seems that even without changing the wheel bearing size, you could increase the torsional strength of the axle by well over a quarter... That's not even changing the material, but would be useless to you unless you did something to allow you to use bigger splines on the centre end. If you cared about the increase in mass this would give you, no reason why you can't gun-drill the axles.

Edited by Heath, 19 July 2010 - 04:44 PM.

[greens nice]

bloke who built my diff said he has seen alot of banjos with falcon centres, not sure whether he meant the old fairlane 8.8 or the b/w 78.

[76lxhatch]

One wheel burnouts with open centres seize the spider gears to the pin which then breaks the roll pin and spins in the housing, chewing it out and effectively creating a heap of backlash as the holes become oval. LSD centres wear the cones and pit the shim faces quickly because they are so small.

Other than the above, the centres themselves aren't too bad considering the small size, however once you fix those problems you start destroying axles. Coarse spline axles twist (and break) at the spline, fine spline are a lot better but still only toothpicks.

If you manage to get a good combination of centre and axles, you start to put strange loads on the poor Banjo design (the removable diff head). The main housing isn't solid enough and you end up with twist that moves things around where they shouldn't be, end result broken bearing caps, cracked and bent housing.

Gearsets are OK (again given the size), but they get a hard time when all of the above starts happening.

[rodomo]

Weak point is the "U" bolts that hold the tail shaft in.
Leave them out.
You'll never break one then.

[wot179]

The fact that they only have two pinion gears probably makes the standard centres a bit limiting. I've never blown one up before but I gather they often shear the pin or strip the teeth off the planetary gears?

Your not trying hard enough, try driving the crown wheel out the back of the housing (third member)

Heat is probably a pretty significant problem with such a small diff, particularly if you're doing standstills, but you can always run thicker oil or use a diff cooler in more extreme cases

HEAT HAS NOTHING TO DO WITH IT

Has anyone here ever made up a set of axles for their car? What material? Can you weld a flange onto the axle and then machine it? or does it have to start off as one piece of billet?

The axles are the strongest part...

How strong do you reckon it could be? Still using the standard 3rd member, diff housing, pinion, crown wheel, bearings etc, just put a decent crush tube on the pinion for good measure.

Weak as piss.

"why would you bother"

If you have to ask, you will never know...

[TerrA LX]

If you manage to get a good combination of centre and axles, you start to put strange loads on the poor Banjo design (the removable diff head). The main housing isn't solid enough and you end up with twist that moves things around where they shouldn't be, end result broken bearing caps, cracked and bent housing.

Gearsets are OK (again given the size), but they get a hard time when all of the above starts happening.

Agree, pretty much a bad design and too small for any creditable power, the salisury bango is far superior in design.

wot179 seems to have hit the nail on the head.

[rexy]

Heath, while im sure its an interesting intellectual exercise for you to ponder the mysteries of the banjo its pretty clear you are on your own.
No one seems interested (and rightly so) in spending money on something thats still going to break. Useable spares are cheap as chips anyway which pretty much takes any market away for your ideas.
R

[orangeLJ]

Rexy, banjo bits may be cheap at the moment, but there will come a day when they arent so cheap, and for those who like to drive their original cars like they were designed (hard, like CraigA for example in his LC XU1) might be very interested in strengthened banjos.

It would definitely save the hassle of fitting the queen mary 9 inch (added weight) or a commodore borgy.

The banjo fits, it works etc etc.

*touch wood* Ive never busted a banjo either, and Ive given both my old open centre and my LSD a pretty hard time (mainly through 205 or 215 tyres though)

it only seems to be the LH/LX guys that hat banjos (obviously the V8 thing and wider tyres makes the difference)

[76lxhatch]

Depending on how you look at it, there is either everything or nothing wrong with the Banjo - they are just a small car diff.

[TerrA LX]

Looking at several busted centres I can't seem to see anything good.

[wot179]

Playing with banjos appeals to all kinds of folks.




.
http://www.youtube.c...h?v=1tqxzWdKKu8

Edited by wot179, 20 July 2010 - 04:47 PM.

[Heath]

the salisury bango is far superior in design.

Absolutely agree. But I do find it funny how lots of people bag the design of a Banjo but don't bag the design of a 9"? If a 9" with all the "good bits" can handle like 700ft.lb then why can't a Banjo be made to handle like... 300ft.lb? I reckon it's just because people don't try - they'd prefer to put 40kg worth of unsprung mass in their rear end, after blowing up 20 unserviced centres. I don't view it as a commercial thing. People just upsize their diffs anyway. It's an intellectual mechanical exercise, my interest in cars is not monetary.

I think the Salisburys are a nicer setup but building Banjos is definitely a more enjoyable activity. If someone wants to pay me good money to build Banjos then I might do it but that isn't my intention.

[Heath]

One wheel burnouts with open centres seize the spider gears to the pin which then breaks the roll pin and spins in the housing, chewing it out and effectively creating a heap of backlash as the holes become oval.

Ok.

HEAT HAS NOTHING TO DO WITH IT

I'm not convinced.

[TerrA LX]

the salisury bango is far superior in design.

But I do find it funny how lots of people bag the design of a Banjo but don't bag the design of a 9"?

Doh, their bigger, they can handle more but still suffer from the same inherent design of the banjo.

I think the Salisburys are a nicer setup but building Banjos is definitely a more enjoyable activity. If someone wants to pay me good money to build Banjos then I might do it but that isn't my intention.

There is no difference in building either.

[Heath]

Shims, a big long heavy housing that needs to be deformed to allow you to fit/remove the carrier without using force?

I'd prefer to just yank my centre out and take it to the shed

[rexy]

Yes, I broke a few teeth off a 308 lsd centre! Also numerous other failures. It seems the banjo likes to mix it up when it comes to failing to proceed.
They really are not worth the effort unless you have a stocko six and drive like a granny.

[76lxhatch]

bloke who built my diff said he has seen alot of banjos with falcon centres, not sure whether he meant the old fairlane 8.8 or the b/w 78.

yeh, B/W spider gears, but fine spline only i guess

How so, the Borg Warner is 25 spline but Banjo is 23 (or 10 for the coarse axles)?

[rexy]

A contact of mine who specialises in evaluating failures in mechanical parts looked at the last banjo axle I broke many years ago. The type of failure was categorised as an overload failure. This means the part was simply too weak to handle the force applied to it. No evidence of heat or fatigue related changes contributing to the failure.
This was behind a not quite 1hp per cube 308 with crap low grip 205 street tyres.
The bits are simply not made to withstand much load.

[rodomo]

The bits are simply not made to withstand much load.

As already mentioned, grey motor technology.

A billet bit that the carrier bolts into (3rd member?) and another billet bit the the crownwheel bolts onto (carrier?) and a press fit spider gear shaft (rather than interference fit) would be the only way that I can see to make these near bullet proof....................?

Then all you need to fix would be the chewy gum axles.


Dowelling the carrier cap bolts and fitting 4 housing to banjo dowell bolts would be a start. (same as pressure plate dowell bolts)

Sleeving the spider gear shaft hole to make the spider gear shaft a press fit would also be a step in the right direction.

A small salisbury (UC) might accomodate a cradle between the carrier caps?

But.....then.......you've still got chewy gum axles?

Edited by rodomo, 22 July 2010 - 12:52 AM.

[turbotrana]

As a few of you may know I have a dyno comp proven (several times) 500rwhp turbo 202.

I run a fine spline LSD and would like to point out the following,

A course spline open centre is weak as piss.

However a fine spline LSD is very strong.

I run soft compound race tyres but not slicks. I dont give stupid abuse but will do long straight burnouts that keep both wheels spinning at equal speed.

I can bust course spline axles in 2 secs and open centres break very easily. You will break either the spider gears or work the pin lose to the point it slides out and destroys the gears.

However I have never ever broken a 23 spline axle or crown and pinion. The only time I damaged spider gears was when I tramped it at the drags but this is expected for any diff. However I have found that the Lsd cones do wear quickly.

One time I got the car airborne and accelerated as it landed and busted the carrier caps and totalled the diff. After this experience I had a heavy steel bar machined to support both caps and I feel this has made the diff much more stronger.

However the biggest problem I have is bending housings into a banana shape over time. The shear torque of the engine will bend the housing and when I have time one day will have extra ribbing welded to give strength.

So whilst I give respect to the capabilities of this diff, the LSD fine spline is not as weak as some make it out to be as they are transferring their experience from the course spline axles and open centres and generalising about the LSD fine spline.