rear axle shafts material

[firstboaz]

hi,
I'm from BGRacing, a team from Israel. in the last 4 years we used titanium for the rear axle shafts.
This year we're thinking on changing the material because of availability and budget issues.
I wanted to know which materials are recommended? and which you have experience with?

thanks

[jd74914]

Titanium-interesting. Why did you use that?

Typical axle materials are 300M or 4340.

[scotty young Taylor Race]

firstboaz

Over the last 18 years we have made our axles out of 4340 , And have switched in the last 4 years years to 4130 with an HRC 42-47

Scotty
Taylor Race Engineering

[StefStam]

Why dont you use carbon half shafts????????????????????

[mech5496]

Depends; no single right answer here as well. We have played with 4130, CK60, Aluminum and CF over the years. What are the performance indicators you are interested in? Weight, inertia, stiffness, cost, recyclability, bling factor?

[BillCobb]

Whatever you do, make the left and right side drive shafts different torsional stiffness, especially if your LSD is tight.

[MCoach]

Why dont you use carbon half shafts????????????????????

Do you? That would personally cause me too much concern to consider such a high risk, low pay off option...



Whatever you do, make the left and right side drive shafts different torsional stiffness, especially if your LSD is tight.

Really, I'd just prefer a spool and call it a day...

[StefStam]

Do you? That would personally cause me too much concern to consider such a high risk, low pay off option...


Well,if you do the right calculations and select the proper fiber orientation,why not :)

[FrederikWe]

Well,if you do the right calculations and select the proper fiber orientation,why not :)

How do you design the force transmission between the CF material and the connectors to the engine/wheel hub?

Probably the more interesting question over the ply layup... I don't see why CF should be the clear & obvious "best choice".

[StefStam]

How do you design the force transmission between the CF material and the connectors to the engine/wheel hub?

Probably the more interesting question over the ply layup... I don't see why CF should be the clear & obvious "best choice".

Thats the tricky part. I guess doing proper connection between CF and any steel/aluminium parts between those will probably eliminate those problems
Well i guess the transmission guys here calculated that each halfshaft must cope with 1270 Nm torque.... Textreme Carbon Fiber with 0/+45/-45/0 will be the proper orientation...even the company
recommends that lay up for torsional applications....... ex. halfshafts :D

[JT A.]

Thats the tricky part. I guess doing proper connection between CF and any steel/aluminium parts between those will probably eliminate those problems
Well i guess the transmission guys here calculated that each halfshaft must cope with 1270 Nm torque.... Textreme Carbon Fiber with 0/+45/-45/0 will be the proper orientation...even the company
recommends that lay up for torsional applications....... ex. halfshafts :D


Why wouldn't it be better to have +/- 45 degree weave in the outermost part of the lay up? Better for handling torsion and better crack/impact resistance than 0 degree uni.

[Z]

This is the really interesting one.


firstboaz

Over the last 18 years we have made our axles out of 4340 , And have switched in the last 4 years years to 4130 with an HRC 42-47

Scotty
Taylor Race Engineering

Scotty,

I am guessing the switch was a "cost-effectiveness" vs "outright-performance" decision?

But how do the two compare just on performance? And is it mostly about the heat-treatment (or shot-peening++) rather than just the raw material?

Z

[jd74914]

I agree with Z there. Switching to 4130 is a bit curious-it would seem like a cost/availability-driven switch but I'm curious to hear from Scotty/TRE.

[Z]

To be clear, I think the switch from 4340 to 4130 is an example of very GOOD engineering. A valuable lesson that students can learn from. Especially since it took TRE some decade-and-a-half of real world testing to discover this lesson.

My technical understanding is that it is the 0.30 - 0.40% Carbon in the above steels that adds most of the strength to the raw Iron. The extra pinches and dashes of Cr/Mo/Ni/Va++ in the 41xx and 43xx "alloy steels" are there mostly to help get the heat-treatment effects deeper into thick sections of the workpiece.

But since an FS-sized axle shaft, especially if it is a hollow tube, has a smallish section thickness, I guess some plain old 1030 or 1040 "medium carbon steel" might be enough to get the required performance. Assuming, of course, that it gets the right processing in terms of heat-treatment/shot-peening/cold-rolled-splines, etc., which seems to be the real "secret ingredient" in all this.

Still interested to hear what Scotty can add?

Z

[firstboaz]

we decided to use titaniun in the past because of hardness to density ratio and the availability of the material to the CNC workshop we work with.
it worked well for the past 4 years, this year we're using the car from 2015 for drivers training and in the last test drive the one of the shafts broke.
so the question of using other material came up again...
attached some photos of the shaft
1115111611171118

[Tim.Wright]

The shaft broke because the design is wrong, not because the material is wrong.

http://www.taylor-race.com/pdf/axle_length_&_circlip%20groove%20de.pdf

[firstboaz]

we know there was a problem with the design. also we're considering to change the material in the same time.
we made the shafts too long the last time and shorten them after, so there is a "spare" groove in the spline for the circlip.

[Tim.Wright]

Apart from that there's a note in drawing about the depth of the circlip grooves you should take into account.

[Claude Rouelle]

For the students who use OptimumKinematics, a quick reminder: you can use math channels and attach one point to the suspended mass (basically your inboard CV joint center) and another point to the non-suspended mass (basically your outboard CV joint center) to calculate your drive shaft length (and therefore see if there is enough plunge) and angle.
You can create one or several simultaneous basic motion(s): roll, heave, pitch, steering (if you would have inboard front electrical motors) or simply input the suspension linear potentiometers data from your data logger to make a track replay to look at your drive shaft plunge and angle along the circuit.

[scotty young Taylor Race]

We made the switch around 2 or more years ago . The main reason was to keep the cost down . Gun drilling every single axle was not only getting out of control price wise, But delivery times where killing us . and the teams
We also increased the ID to .500 . This was a great weight savings . We did our own testing . TRE owes some SAE cars so all our stuff gets beat up pretty good . Changes had to be made, Or else axles would be $300.00 +.
We have delivered at least 750 axles since the change . The only failures are due to Circlip Groove neglect . You can make an axle out of heat treated billet moon rock and spend $2000.00 per axle.... but if you cut your inside circlip grooves too deep. they are gonna break every time

[scotty young Taylor Race]

Here is a proper groove .