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MG Midget and Sprite Technical - Frontline fine spline half-shafts

I am building a midget for competition use,Auto-tests, retro rallies etc…I want to use the original axle and don’t want to fit the Ford Anglia axle.
Has anyone info experiences regarding Frontline fine spline half shafts and LSD's.
Has anyone broke one yet,
Any other Heavy duty solutions.
P Blair

Paul.

Hows it going

Both Hill Scotts old car and Wills Midget both are using the fine spline shafts.

Removed and checked after most events and still never even found remote sign of twisting or stress.

The other solution is the Peter May ones, but i have zero experience with these.

We swear by their shafts to be honest, one of the only things that hasnt failed us at any point.

Hope that helps

Pete
PeterJMoore

when I looked into this last year, here is what I found:

- stock is EN17 (after '67)
- Peter May makes EN24 shafts.
- Frontline makes EN40B nitrided shafts.
Peter May says that "EN24 provides the best balance of strength and toughness". I expect FL says the same about theirs.

Another option is to "growlerize" your stock shafts (machine off material to eliminate the stress risers). Do a search of the archives here under that name and you'll find the details:

Growlerize the shafts to minimize both the original stress riser where the spline cut ends, and also from the wear caused by the edge of the differential gear against the spline.
Growlerizing (named for the screen name of Grant Bowyer, the Kiwi machinist on the MG Enthusiast BBS / UK who brought it to wider attention) means to cut down the diameter of the shaft to the root diameter of the splines, so the land between the splines stick "out", rather than the splines themselves sticking "in":

Start the cut 1" from the end of the shaft (so that the very ends of the differential splines are over air, not against the face of the splines), and provide a generous radius at the end of the splines (this photo shows too sharp a transition, a big radius would be better). Continue the root diameter for 4", then gradually taper over 6" back to the original diameter. De-burr and then shot peen (like is done with a connecting rod). Why does this work? The shaft itself is plenty strong enough to handle the engine torque, so reducing its diameter near the diff, although it gives up some torsional stiffness, is offset by the benefit gained by avoiding cracks at those two eliminated stress risers: the sharp corners at the end of the spline cuts, and where the diff splines end.

hope this is helpful,
Norm






Norm Kerr

Don't forget this option
http://www.bighealey.co.uk/category/catalogues/sprite-midget/axle
David Billington

Norm,

Thats a lot of machine work for something that will still snap when used in anger on the likes of the autotests.

This isnt like autosolos where you have 3 acres to play in, its all tight, with harsh direction changes, fast and hard transmission loadings.

The weak link is the shafts, and those who have been around the autotesting and classic rallying over here long enough still stay as far as possible from anything to do with standard shafts.

the options for tough back axle are either finespline or ford it really is that simple.

Again, no doubt someone who races will be on to state otherwise, but again, your loadings are light compared to ours. Variying surfaces, high wheel rpm abruptly interrupted by the handbrake and followed by clutch drop and acceleration and of course you have direction changes too, anything to do with standard shafts will last about 35 seconds.
PeterJMoore

I growlerised 2 pairs a few years ago and they all have been fine. The car does a good few autotests & autosolos, although I am not using a very powerful engine or grippy tyres, the cost was about £40 per pair.

What Norm describes doesn't take that long to do, but does require good cutters on the lathe, and the shot peen after is important.

The half shafts from Dennis Welch that David has posted are the only properly designed ones out there (on a std spline) they are about £220 each IIRC. About double the price of normal H/D shafts from P May, Magic Midget etc

A lot depends on your driving style as illustrated by Russ Morgans K Midget withover 200bhp that has been running std shafts for more than 15yrs, he tends to break diffs before shafts.

But buy the best you can afford, if your having a LSD built up then adding the Frontline fine spline gears (required) will be easy at the same time, its the best option for the standard axle.

Ian
Ian Webb '73 GAN5

Can’t believe the super fast response from everyone to my enquiry,
Any other further comments on this subject will be appreciated.


Many Thanks
P Blair

Your welcome to come see Roberts next time they are removed for checking!
PeterJMoore

Ive got Frontline fine-spline shafts, LSD, and double bearings when my car converted to Kseries.
No problems yet(5 years of running K) knock on wood. ;)

Busted 2 standard shafts and 1 Peter May special shaft with my 1500 engine.




Arie de Best

I would go the Peter May half shafts any day of the week - especially for Autotests - depending on what sort of LSD you're running and your driving style
rachmacb

rach - one post above yours is the guaranteed outcome
PeterJMoore

Arie,

If I ever come for a visit, would it be okay If brought my own tolit paper?

Ive got a tough little fun hole but I dont know about using broken half shafts... LOL

Im eventually doing the RX7 rearend with LSD/disk brakes

Prop
Prop

Prop, its the bathtub, not the toilet although ive been told you can take a sh*t in it only it flushes more diffecult. ;)



"Ive got a tough little fun hole"

Prop, I dont understand, can you help us visualize it with a photo?

DONT!!!!!!
Just kidding, youll be banned from this bbs for life!
Arie de Best

For what it's worth I've used Peter May's larger splined halfshafts for circuit racing for at least 10-12 years with no problems at all. With and with out LSD. (After having broken the "original" EN27 competition type on the kerbs at Mallory)
Mark Lister

We've used the Frontline finespline LSD with halfshafts made to our own spec in 2767 for 10 years of autotesting with 185BHP K engine and sticky tyres without any failure. As Peter comments above, autotests are the toughest on drive train by far ... add to his list that all this action is in first or reverse so the torque the rear axle sees is much greater than in higher gears.

The fine splines spread stress within the halfshaft much better than the original coarse square spline pattern, both due to the increase number and the V shape. They also retain a larger root diameter, so the halfshaft is effictively thicker.
There is also a stress raiser at the end of the splines when they are cut into the shaft. "Growlerising" removes this stress raiser and should be done whatever halfshaft is used.
Paul Walbran

LOL Pete - Arie uses every opportunity to push Frontline like a candy shop outside a school yard ...!

At the end of the day - you pays your money, you takes your choice - there will probably be just about equal numbers recommend both!
rachmacb

Sorry - bit of a senior moment - the original competition halfshafts are EN25 not EN27 as I said earlier.
Mark Lister

Rach

i do agree there will be equal numbers

but already we are having replies stating

"for circuit racing for at least 10-12 years with no problems"

we arent talking about Circuit Racing

or going for a summers morning tear throught the countryside in a k-midget

we are talking about kicking every ounce of life out of rotating components that simply are not up to the job of changing torque and directional loadings in such a harsh and vigourous way.

If you have seen how Mr Blair autotests, perhaps you would understand this is not wanting a stop gap, this is wanting a guaranteed reliability - and that is IMPOSSIBLE with the standard shafts and variations on standard shafts no matter how many years you have used them for picnic runs.

This is one of the only things that really really annoys me on here is that people cannot compare like for like, so i apologise if any of this comes across a bit harsh, but anything with standard spline is pure and utter sh*te!!!
PeterJMoore

"LOL Pete - Arie uses every opportunity to push Frontline like a candy shop outside a school yard ...!"


Rach, have you actualy read the tittle of this thread?
Please do and realise Im not pushing Frontline but simply anwsered on the title.
Isnt it you in this thread pushing Peter May''s stuff?
LOL!!

Ive had my ups and downs with Frontline but I can honestly recommend their rearaxle improvements.
Little note is that the drumsprings run against the double bearing and eventualy break off.




Arie de Best

Paul

If you indend to run rear discs, do not run double bearing hub kits

You will have to replace pads after each run on a test as the seals are pure pish even on the best of axles.

We suffered very very badly with diff fluid literally pouring out each end of the axle, standard hubs are the way forward with wolseley 1500 drums
PeterJMoore

Thanks again everyone for all your comments some of which have gave me a laugh.

I have seen quite a few Peter May & Frontline coarse spline shafts snap as per Arie's picture, so I don’t want to go down that route. I have an Anglia axle which I know is extremely reliable but is very heavy compared to the Midget axle.

Does anyone know if the Frontline Fine spline is the same spline / pitch as the Ford ?

Peter thanks for your input here as you know what type of events I hope to be competing in, I spoke to Will a few days ago about what shafts he was using and he recommended the fine spline shafts.
P Blair

Lol I only call what I see and having seen some of the cars belonging to people on the BBS .....

As I say to any newbie, only take advice from people who have cars that actually run!

Disc brakes does kind of change the point anyway ... - gotta love it when people change the situation!!!!!
rachmacb

tangentially to the question, is it easy to do handbrake turns with rear discs? I've never found an effective handbrake in this situation.
David Smith

I also have the Frontline(herewe go again Rach) ;) reardisc kit on my car and although one side leaked diff oil when I got it back from Frontline, after I fixed it it has been fine untill now.

I cant comment on Pete's experiences as ive not used it on tarmac road tests yet nor have I done intensive handbrake turnings but the setup looks firm enough to be able to handle handbraketurns.

Not realy visible on this picture...


Arie de Best

Better but still no perfect picture



Nice shiny(read oily!) disc from the leaking double hub-bearing


Btw as you can see the handbrake is cable-opperated


Arie de Best

I have Frontline set up which leaked continually until I fitted Speedi Sleeves.

http://simplybearings.co.uk/shop/product_info.php?products_id=182270

Don't do any hand break turns but all works well and no leaks now for 3000 miles.

Regards

Gary
G Crouch

I haven't had chance to read all the posts above but I think I understand the jist of things! I just wanted to pitch in with my experience of driveshafts and splines from when I designed my single seater racer. I will try not to get into too much detail, but apologies if I get carried away! I would also like to point out that I have no experience of racing Midgets or their driveshafts.

I/we (the team) had a set of steel shafts for the car which were increadibly heavy. We were able to get a machine shop to 'scan' the spline profile and create us a cutter to cut the exact same spline profile. We then used this cutter to cut splines into some off the shelf high strength 7/8" OD aluminium tubing using the CNC machine at the uni. They were super light and didnt break (despite all the none-engineers saying they would!). The engine was a 600cc motorbike engine and put out 90hp and about 60Nm of torque if I remember rightly...

Anyway, I wouldn't advise using aluminium for your shafts as fatigue will probably become an issue! But the point of the story is that a good machine shop could manufacture splines/shafts to the required spec quite easily, you would just need to find some good steel.

Using tubular steel would give you a good weight saving as the centre of a driveshaft transmits no torque and is therefore pointless. This also provides benefits of (slightly!) less inertia in your drive train.

I am a little ropey on my materials engineering (especially with steel) but I dont think the toughness of the steel should be an issue and you should look for the highest strength steel (within reason). You could get them dye penetrant tested fairly cheaply to ensure there are no surface breaking cracks also.

Anyway, sorry for the long post, I think there was a point in there somewhere...

Malcolm
M Le Chevalier

Arie,

We built it up on the cleanest axle we could find.

Sufferd the same problem time and time again despite new seals, even a change to felt seals to try and allow the crud to seal it up.

Much in the same way the rear main seal "upgrade" only lasts a minimal length of time.

We also had to machine the calipers as they arrived as brand new VAG calipers untouched as as such they didnt fit under the 13" minators.

Paul, BZ runs on the wolseley/Riley 1500 rear drums and althougha hydrauic handbrake is installed (down the right hand side of the drivers seat) I just cannot get used to it and used the standard cable operated handbrake all the time, with the larger rear drums and lack of leaky hubs, the handbrake in BZ has been nothing but reliable, sharp and precise.

Definitely without going down the anglia axle route, the finespline stuff is the most reliable by a farmers mile. You have seen how Will drives his with absolutely zero regard for shafts and they have proven to be the single most reliable upgrade we have encountered.
PeterJMoore

Hi Malcolm,

Interesting post, Racing cars run 'proper' driveshafts, usually with UJ's at both ends. The problem with Spridget halfshafts is that they only have a coarse spline on one end (have a look at the link to the Welch shafts posted above by David Billington) with a fixed drive plate at the other. The spline is machined 'into' the overall diameter raising a stress point at about the place the shafts have snapped in Arie's picture.

While hollow shafts would work with the torque and power output of most Spridgets, the design of the axle would mean that oil would pour out of the axle end unless it was plugged. One could drill out the centre of the shaft for most of its length I suppose but that would be an expensive proposition compared to using steel tube. Ultimately if the Frontline shafts don't break then that is the answer.

As a racing bod I've used Peter May halfshafts for years - never broken one (unlike gearboxes), but as Pete Moore says the loadings are different for Autotesting.

Cheers

JB
James Bilsland

P Blair
Regarding the weight of the Anglia axle have you considered converting the iron diff housing/casing to alloy (sold by all the regular Ford comp parts supliers)or maybe you have already done that. It saves around 4.5 kg .....I am assuming here that Anglia axle is compatible with Escort english axle parts.
I suppose the unsprung weight of the axle is more of an issue for you when rallying rather than autotesting ?

Pete....you really should avoid getting up your high horse sometimes.
We are trying to reply to the original thread question, part of which was "Any other Heavy duty solutions ?" and we dont at that point know how much the questioner knows, and how much he wants to spend, which at the end of the day is often a deciding factor.

Whilst on the subject I guess you are running TranX or similar plate LSdiffs, which spec of Tranx ramp settings do you find most suitable for the mix of events you do ? I ask because I am thinking of changing my Quaife diff for a TranX sometime this year.
Ian
Ian Webb '73 GAN5

JB,

I do admit I know very little about the Midget rear axle as it is the only bit still attached to my body! I was just throwing in a bit of my (albeit limited) engineering experience to see if it sparked any great ideas! Ultimatly I agree that an off the shelf soloution would be best.

Perhaps another thing to look for would be to ensure everything is dead straight, reducing any untoward bending on components that are not designed to bend as this will quickly knacker things.

Or go really hightech and adhesivly bond splined ends into carbon tubes... Now I really am going off topic!

All the best,
Malcolm
M Le Chevalier

Unless you go for the double bearing hubs you'll need to take into account the bending loads on the half shaft as well as torsional issues. I think the standard type are referred to as semi-floating and the outer bearing holds the halfshaft in place but the halfshaft in bending is what prevents the wheel deflecting.
David Billington

I drag race an A series turbo and the experience of myslef and others in this arena is that the Peter May shafts in EN24 do twist and will eventually break,

I now use shafts made in EN30 with the drive flanges splined on, not on a taper like the PM ones.Time will tell, I suppose.

The growlerising idea is interesting, but having to have them shot peened afterwards is a bit of a pain.
D.G. Clark

We used EN30 in earleir versions of our halfshafts. They last very well, but not for ever. The 2767 we use now has performed better.
Paul Walbran

This thread was discussed between 23/02/2011 and 12/03/2011

MG Midget and Sprite Technical index

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