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Carbon fibre rigid axle?


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#1 mariner

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Posted 09 December 2017 - 19:53

Carbon fibre driveshafts now seem to be commonplace and the technology of fixing the CF tube onto a metallic UJ yoke seems reliable.

 

So why not a fully CF rigid axle with just metallic parts for the hubs and gears?

 

The half shafts can clearly be CF even if they may need to be quite large diameter. The axle tubes can be CF with alloy outer hubs for bearings and caliper attachment.

 

The central diff. casing can also be moulded CF and probably mated to the CF outer tubes by rings or adhesive bonding. Being custom made negative camber can be designed in.

 

Rigid axles have their limitations of swing arm length equals track and inner tyre tilt but most IRS with an ARB moves the inner wheel angle  too.

 

Arthur Mallock showed with his " trailing arm magic" just how good a well designed axle can be. A Mumford link allowed a rear RC wherever you want it and the non equal and non parallel trailing arms countered squat and cross axle weight transfer.

 

Also it is often much easier and liighter to design the well spread out  solid axle attachment points than closely positioned IRS links near the car centre line.



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#2 Greg Locock

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Posted 09 December 2017 - 20:32

For a circuit racing car a solid rear axle (if they are so good why not front axle?)  is probably not too much of a disadvantage. As soon as you have to deal with single wheel bump, ie potholes kerbs or rough roads, then a beam axle slows you down. If anybody starts muttering about Jeeps, I think that their setup is cost effective for what it offers, but an independent suspension could be designed to beat it. For high speed off roaders there's no doubt that all independent buggy type vehicles are faster than the big old truck based ones, and cost a quarter as much.



#3 Lee Nicolle

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Posted 10 December 2017 - 05:35

I really do not understand the fixation with c/f components on road cars. A tailshaft made from steel is yes a bit heavier, but has been proven 100% reliable if engineered properly. A tailshaft has little centrifigual mass so is not a major component. A c/f wheel for instance is,,,if it can be made economically and reliable. And that is not yet. Ford have a major leap of faith! Since I see daily what happens to alloy and steel wheels. C/F may absorb some impacts but in the long run it is going to fail. And they are very expensive, maybe a good thing on race cars with strict lifing. But that is about it for me.

Horses for courses, in speedway independents have been tried on midgets, Noel Hurd was one such owner and he is a clever bloke. There was no advantage traction wise and it was ofcourse heavier. It has been tried in the States as well. 

As for carbon fibre panels on road cars,,, I suspect the insurance premium will be far higher as the costs of repair/ replace is a LOT higher. You have to think practical!

As a matter of interest having worked with fibreglass is c/f totally repeatable? As fibreglass is not, every panel varies, that is why some of those body kits we see are butt ugly in fit [and usually execution as well] from what I have seen kevlar is a bit better but never good. Unlike steel pressings these days that have miniscule tolerances.



#4 bigleagueslider

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Posted 10 December 2017 - 09:02

Hey, all it costs is money, right?

 

A carbon composite driveshaft provides a couple benefits for race cars, including reduced drivetrain inertia, increased critical speed margins, and lower weight. But there is also added cost involved. For the typical RWD road car, there are many other ways to use expensive carbon fiber composites that provide much better economic value.



#5 mariner

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Posted 10 December 2017 - 12:02

I was mainly talking about race cars in terms of building a CF axle.

 

Rigid axles aren't ideal but the lap times of various Mallocks fitted with them have always been seriously quick on smooth UK circuits. 

 

 Of course it may not be cheap but not much in racing is. I would think the CF outer tubes and driveshafts would be affordable as firms  now supply these for racing.

 

https://www.qa1.net/driveshafts

 

 

http://www.pstds.com/

 

The alloy hubs are pretty much standard stuff so only the centre axle housing in CF is new. I would presume with all the knowledge on formula CF gearbox housings that isn't impossible.



#6 Lee Nicolle

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Posted 25 December 2017 - 10:04

There is no real reason why besides the expense a c/f diff tube or even complete housing could not be made besides very high cost and it would be non standard sizing as It would have to be bigger to attain the same strength.

most diff tubes are high grade 3" 1/8" [or more] steel tube. U bolts, suspension mount brackets are all in that dia. Though attaching the suspension to the tube would be a real drama, all clamp on as you cannot weld to c/f.

I have seen diff tubes fail in steel. Why? I have no idea though possibly faulty tube. I have seen 3"x 1/4" wall open axle sprintcar axles break too a few times and they are ugly as it is all jagged. The reasons the big American teams life them severely. Obviously used as a tube would suffer less twisting. I feel though that any weight advantages c/f would have would be offset by difficulty in mounting and attaching to banjo housings. Never though for a Salisbury style diff. But these would have to be made in large numbers and would always be very expensive and near certainly less reliable as well. Look at Nascar, one of the few things not very regularly replaced is the actual diff housing. Though I am sure they bend a lot in accidents. They bend them to get camber and toe though, again not something you can do with C/F. [and yes they use 'ball' end axle shafts and only bend them a small amount. eg 1.5 degrees]

 

Carbon fibre tailshafts do fail in drag racing and have to be larger diameter to attain strength, eg a steel 3" tailshaft is about equal too 3.5 in alloy and 3.75 or 4 " in c/f. It possible would dampen drivetrain viabration. But would be a chore to get under the car. I actually bought a alloy tailshaft for my Falcon racecar as Ford used them for a few years. BUT it was 3.5" and the steel 3" ones rub on the floor now so I was not very clever!! Though eventually made a few bucks on it. And I have been told that the dragracers have twisted them. This on street drag radials.



#7 pugfan

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Posted 11 January 2018 - 10:49

... if they are so good why not front axle?...

 

I see what you did there.



#8 Lee Nicolle

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Posted 18 January 2018 - 06:17

Just as a matter of interest some production cars and commercials use fibreglass leaf springs. 

Some Mercedes vans do, and are far from ideal when fully loaded, and that means max load day in day out but no more. A friend had one as a work van and they could not get a spring of any kind to replace it .

Corvettes have in the past on the reputedly old fashoined transverse leaf. But near impossible to change ride height or spring rate unless you go back to good old steel!

I ran the c/f diff housing past a long time race car builder and he said WHY?  The cost would be prohibitive and attaching the housing to the car would be near impossible unless way over engineered meaning as heavy for 10 times the cost.



#9 Lee Nicolle

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Posted 18 January 2018 - 06:22

I see what you did there.

Yeah I have a car with a beam front axle,, only 50 years old and it is worn out! It is made from 2" steam pipe which is I believe 1/4" wall. But how di I attach the king pin eyes too the axle. And how do I attach the spring mounts and suspension pick ups. 

Probably doable but a 2.5" 1/8th wall chrome moly axle for about $200 takes a LOT of beating for strength and weight



#10 Charlieman

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Posted 20 January 2018 - 11:47

I recall a fairly quick clubmans car in the 1980s which used a front beam axle. I imagine it working well on even surfaced ex-airfield circuits like Silverstone, less well at Brands Hatch. There may even have been some useful features when aero side pods were allowed.



#11 mariner

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Posted 23 January 2018 - 08:15

Past the vintage era - whose cars go well on modern smooth racks - front beam axles pretty much vanished due to steering kickback and installation problems.

 

The last serious attempt was, I think, the 1968 lotus 58 built as a F1 test bed using an F2 FVA engine. It was aimed at utilising the new , wider tyres but a combination of indifferent test results, Jim Clark's death and then wings meant it was never raced.

 

I have been lucky enough to examine the car and its drawings and getting the front axle in was tricky. It is multi tube beam with the steering rack mounted on the axle itself so the column moves up and down. That way there is no steering arm conflict. The tops of the spring / damper units are mounted on curved "horns" from the chassis more befitting a sprint car than a Lotus!

 

I can think of only one possible application of a beam front axle today which MIGHT work - on F1 cars. They seem to totally disregard all geometry rules up front with sky high roll centres to get a aero gain from a higher nose so maybe a beam axle won't matter.

 

The benefit would come if you can make the axle beam rotate and be of a large diameter i.e a cylinder. When you rotate a cylinder there is an aero force at right angles to it. This has been used instead of sails on boats. Conveniently it is straight down on a cylindrical axle roatating forward so more down force and possibly less upset by the car in front than a wing.

 

The actual mechanical design would be very diffficult but, hey, that never stopped F! when in pursuit of more aero downforce.


Edited by mariner, 23 January 2018 - 10:33.


#12 blkirk

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Posted 23 January 2018 - 15:42

The benefit would come if you can make the axle beam rotate and be of a large diameter i.e a cylinder. When you rotate a cylinder there is an aero force at right angles to it. This has been used instead of sails on boats. Conveniently it is straight down on a cylindrical axle roatating forward so more down force and possibly less upset by the car in front than a wing.

 

And I'm sure every other team would immediately protest it as a moveable aerodynamic device.  But I'll give you points for creativity.  



#13 mariner

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Posted 23 January 2018 - 17:17

And I'm sure every other team would immediately protest it as a moveable aerodynamic device.  But I'll give you points for creativity.  

f

Probably but a drive shaft  has the same effect on small scale so the arguments would be very interesting.!!

 

The official term for this effect is the Magnus effect, some maths for the clever ones.

 

https://en.wikipedia...i/Magnus_effect


Edited by mariner, 23 January 2018 - 17:23.


#14 Greg Locock

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Posted 23 January 2018 - 19:42

It would generate lift not downforce, if the car is moving forward. Carry on...


Edited by Greg Locock, 24 January 2018 - 18:03.


#15 just me again

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Posted 23 January 2018 - 20:31

So they should have gear in the upright. Then the axle will be lower and generate downforce. Just maybe helping the diffuser!!

Edited by just me again, 23 January 2018 - 20:31.


#16 mariner

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Posted 23 January 2018 - 21:23

Maybe I'm being stupid (not unusual) but in this example the air flow is from left to right and the cylinder rotation is clockwise so the cyllnder is moving WITH the airflow on the side that generates the perpendicular force.

 

In other words turn the pic upside down 

 

https://en.wikipedia...bulent_wake.svg

 

So I THINK  that's downforce??


Edited by mariner, 23 January 2018 - 21:25.


#17 Greg Locock

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Posted 24 January 2018 - 18:03

Sorry, you are absolutely right, i was thinking it was the surface velocity and hence pressure differential that was important, whereas it is really the direction of the wake that matters.



#18 Kelpiecross

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Posted 25 January 2018 - 02:05

Sorry, you are absolutely right, i was thinking it was the surface velocity and hence pressure differential that was important, whereas it is really the direction of the wake that matters.


I think you were right the first time - it would generate lift. The basic difference between a "topspinner" and a "backspinner" in various ball games - probably most noticeable in table tennis.

#19 gruntguru

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Posted 25 January 2018 - 11:35

No he was right the second time. A driveshaft is a "topspinner".



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#20 Kelpiecross

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Posted 26 January 2018 - 04:09

No he was right the second time. A driveshaft is a "topspinner".


I have to agree - no wonder I am such a hopeless Ping-Pong player.

#21 gruntguru

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Posted 26 January 2018 - 06:28

Well - I might know the difference between top-spin and back-spin but I am still a hopeless Ping-Pong player.



#22 2F-001

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Posted 26 January 2018 - 17:37

I recall a fairly quick clubmans car in the 1980s which used a front beam axle. I imagine it working well on even surfaced ex-airfield circuits like Silverstone, less well at Brands Hatch. There may even have been some useful features when aero side pods were allowed.


Jim Yardley's Beagle?
I believe it became the first non-Mallock for umpteen years to win a Clubmans championship.
I think I read recently, there was some planning to get it running again this year (in HSCC?) - though it currently fell foul of a detail ruling in Classic Clubmans, to do with flywheel diameter (presumably it is too small).

https://cdn2-img.pre.../OQ==&scale=100

Edited by 2F-001, 26 January 2018 - 17:40.


#23 Charlieman

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Posted 26 January 2018 - 18:08

Jim Yardley's Beagle?
I believe it became the first non-Mallock for umpteen years to win a Clubmans championship.
I think I read recently, there was some planning to get it running again this year (in HSCC?) - though it currently fell foul of a detail ruling in Classic Clubmans, to do with flywheel diameter (presumably it is too small).

Ta. I hope that common sense will put it on the track.