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Motorcycle wheel spindles

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Mark Edwards 113/01/2011 09:12:46
6 forum posts
I race motorcycles and I am upgrading to wider wheels, this requires a new wheel a spindle to be made, nominal diameter 17mm x 240mm long threaded at on end.
What steel should I use ? I model engineering equipment not industrial so I need to be able to machine this at home but it has to be strong enough to do the job
Baz13/01/2011 09:35:18
586 forum posts
2 photos
Hi Mark,
EN8 is a pretty tough bit of steel, but it can be quite easily  machined on Myford sized lathes
John Stevenson13/01/2011 09:39:59
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We used to use EN16 or better still  EN21 if we could get it in the right sizes.
 
John S.
John Coates13/01/2011 12:37:59
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558 forum posts
28 photos
Usually spacers are made to adapt a wheel to the motorcycle to retain the original spindle and fixings (nuts, washers, chain adjusters). The best way is the principle of captive spacers where larger diameter bearings have spacers permanently fixed to speed up wheel changes. This not an option for you? And you have checked the alignment of the brake discs relative to the brake calipers as these can need spacing as well
 
I have a 1999 Kawasaki ZX7R onto which I am putting the front end (forks, calipers, yokes) from a 2007 ZX14 and swingarm from a 2005 ZX10R so am dealing with the same issues
Freddybear13/01/2011 13:53:07
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27 forum posts
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My mate worked at Vikers Armstrong ( now BAE ) a few years back.
 
He made a new spindle for his biker brother. He tested the material of the original at work and it was EN16.
 
However, given you racing application, I would have to agree with Mr Stevenson and recommend something that would be of a higher specication eg EN21.
 
I hear many people talking about TITANIUM race parts, but I have no experience of machining this material.
 
Why not look at a few  race parts suppliers websites, to see what material they spec for their spindles!
 
Above all else, remember that it is your Butt on the line.
 
good luck.

Edited By Freddybear on 13/01/2011 13:54:12

Edited By Freddybear on 13/01/2011 13:55:07

Mark Edwards 113/01/2011 14:34:21
6 forum posts
I am fitting suzuki bandit front end and rear wheel into a race "Classic" YPVS race bike.
The rules don't permit me to change the swinging arm but I am allowed to widen the one I have therefore requiring a wheel spindle approx 15mm longer than the standard one.
 
To answer the above question is no nothing lined up, the brake disc had to be moved 8 mm closed to the centre of the wheel,  talon have supplied a new engine sprocket with 9mm offset moving the chain 9mm outwards, The chain still did not line up so a new sprocket carrier had to be made out of alumimium billet (165mm x 35mm) this moved the sprocket 16mm nearer the centre of the wheel and still used the standard cush drive.
Making the new sprocket carrierr took 12 hours !!! on my chester model B combi machine but it did show just what can be made on basic machinery.
 
We are allowed to run titanium components but not wheels spindles or swing arm pivot bolts and this applies to all race bikes in this country I can only assume it must be on safety grounds. My brother had a set made in titanium and they saved lots of weight but scrutineers started using magnets to check they were steel so that soon put a stop to them.
Mark Edwards 113/01/2011 14:56:51
6 forum posts
I have found a supplier of EN16 or EN16T, which should I use, Would I be able to machine the EN16T ? Or if I used EN16 would it have to have some additional heat treatment afterwards ?
Freddybear14/01/2011 22:32:34
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27 forum posts
54 photos
EN16 should be pretty staight forward to turn / mill.
 
EN16T is supposed to be readily machineable too, but as its already hardened, getting a good surface finish can be a pain. 
 
I have only used the T varient once before, to make a small crank shaft.
A tired old lathe, HSS tooling wasn't liked. ( I suspect the HSS problem has the tool angles). Using T/C tipped tools with coolant worked better, but the finishing cut had to be a bit heavier than I usualy like.
 
If I tried it again, I would probably get any  vital surfaces ground.
 
As it would appear John uses these materials at work, what do you have to say Mr Stevenson?
 
JimmieS29/08/2021 21:59:08
274 forum posts
1 photos

I require a replacement f/wheel spindle for a BSA Bantam racer I am restoring for parade use only. The bike is fitted with an unknown set of forks so buying a spare is out of the question. As my old Boxford is uncapable of turning anything parallel to the tolerance required for such a job, could the spindle be assembled from two pieces of EN8 silver soldered together? Thoughts please.

Jim

Clive Foster29/08/2021 22:33:35
2837 forum posts
103 photos

Jim

The bible for this sort of thing is Volume 2 of the three book series "The Racing Motorcycle, a constructors guide" by John Bradley.

He recommends 605M36 in T condition for wheel spindles. That should be what you get if you ask for EN16T from a reputable supplier but I can't see the sense in asking for something that should be to a long obsolete standard and ought to be equivalent. Ask for the right stuff and be done with it.

Although you could use 080M40 which is what ought to be supplied if you ask for EN8 it's a bit lacking. Only goes to tensile range R at 19 mm diameter so limited to very small spindles. John says you need to make sure that it actually is heat treated to a sensible range and not just plain bright drawn or, worse hot rolled bar. Even in 2003 when that volume was published hot rolled EN "equivalents" could be pretty noisome stuff. Its only got worse in the intervening period. When was the last time you actally say EN8R advertised? Like John I reckon there is too much carbon in it for comfort.

If you only want a foot for a spindle might as well get summat a bit decent.

When it comes to safety related things like spindles the job must be done properly.

No excuses.

Ever.

You may know its for parade only at low speed with a careful pilot but no one else will care. Two part construction just won't do. Not forgetting the effect that silver soldering may have on the tensile range.

If I'm making a spindle I want the right material with certificates.

Clive

Edited By Clive Foster on 29/08/2021 22:34:36

Emgee29/08/2021 22:34:28
2158 forum posts
265 photos

Jim

I would think heating to silver solder the 2 pieces of EN8 would change the properties of both pieces and possibly cause a weakness in the spindle.

Best no doubt to get the job outsourced if you can't bring the lathe up to standard, turning between centres may help to get both ends parallel for the distance required.

Emgee

Bill Pudney29/08/2021 23:02:04
563 forum posts
24 photos

I asked the question of Norman White (Norton restorer of note) "What material are Norton Commando wheel spindles?", his response was "EN16"

cheers

Bill

 

Edited By Bill Pudney on 29/08/2021 23:02:17

Chris Evans 630/08/2021 09:11:18
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1960 forum posts

I keep a good stock of EN16T for wheel spindles and especially girder fork spindles. Pre Covid a local steel stockist would let me rummage around in the short bar length rack for the bigger diameters but up to 5/8" I buy the 3 metre length. The last time I bought some 1/2" diameter EN16T the 3 metre length was sub £15. No compromise on safety critical items.

colin hawes30/08/2021 11:22:50
543 forum posts
18 photos

I don't consider EN8 to be strong enough for this application. I would NOT risk my neck on this material. Colin

Mike Poole30/08/2021 12:16:04
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3073 forum posts
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The material for wheel spindles seems to be an old chestnut, opinions raged over stainless steel for spindles. It would be interesting to know what a full analysis of the stresses the spindle needs to tolerate would suggest. As it does not need too much imagination to visualise the horrific accident a spindle failure would cause then I think the tendency is to go with a material that is known to be used in that application. As long as a material is strong enough then too strong is unlikely to be a problem. The spindles on most road bikes are probably far stronger than they need to be, I have never seen one break in normal use and they seem to survive accidents where the machine is completely destroyed. As the spindle size is determined by the machine designer then using the toughest material available will do no harm. Manufacturers will tend to use the best common material rather than specify an exotic alloy steel. Pattern parts have been made from some poor materials in the past which is a worry for a safety critical part but the regulations for pattern parts have tightened up on the performance of non OEM parts so they should be at least equal to the original, of course some sources pay little attention to standards and regulations.

Mike

Clive Foster30/08/2021 13:11:10
2837 forum posts
103 photos

Mike

Fundamentally the issue with wheel spindles is crack resistance rather than strength per se. Especially with threaded end ones that screw into one fork leg where the thread end creates a stress riser.

Even then odds are is more a case of what happens if things aren't correctly installed with the spindle properly fitted into the master leg and the other settled into its natural position by bouncing the forks.

Agreed that spindles are rarely destroyed in a crash. Seen plenty of bent ones tho'. Something I always check when involved with a bike whose history I'm unsure of. Mild bends are more common than I'd like. Regrettably seen some "professionally" fixed (not) bikes with handling or fork issues where the bend should have been obvious on installation.

When you don't have factory or real engineering company resources / expertise to sort out and get ideal fit material for the job it becomes a question of what can reliably be got off the shelf that is known to be suitable for the job.

605M36 in T condition with a certificate is. Anything else folk like us can't really be sure about. 080M40 in R condition with a certificate should certainly be up to the job on anything small enough to have a spindle under 19 mm diameter. I don't do ordering under an EN number, unless "a bit of steel sort of like this" is up to the job and the price is very right, because I can't get real certificates specifying the properties of what I've just paid for.

Of course, like any sane Home Workshop guy I tend to duck jobs where "a bit of steel sort of like this" isn't an adequate specification!

Stainless steels are a minefield. Pretty but you do need to know your engineering if applying serious loads. Crack behaviour and effects of certain chemicals can be a little surprising.

Clive

old mart30/08/2021 18:20:08
3347 forum posts
208 photos

I would go for en19T or en24T both are chrome moly and are much stronger than mild steel without any further heat treating.

Mike Poole30/08/2021 19:28:39
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I like your reasoning Clive, choosing a suitable material could still be undermined by not taking care with suitable radii in the right places. Making a wheel spindle seems a straightforward job until someone who knows what they are doing explains the things that can go wrong. We had some conveyors at work that would break quite large shafts simply because of poor alignment, the actual loads from the parts on the conveyor were minimal but the alignment being slightly out would in time snap a 40mm shaft, I suspect the design was not too brilliant either.

Mike

hubertus fischer30/08/2021 20:53:51
3 forum posts

how about getting a car-halfaxle from the scrapyard? should be sufficiently strong material but probably difficult to machine.

hubertus

Clive Foster30/08/2021 22:31:58
2837 forum posts
103 photos

Bottom line is any commonly available steel heat treated to T condition will be amply strong enough for spindle duties. When you look a tabulated properties there is no discernible difference so far as the likes of us are concerned.

But I'd still rate 603M36 T (En16 T) over 709M40 T (En 19 T) and 817M40 (En 24 T) for this sort of thing because its a manganese-molybdenum alloy and so much less susceptible to temper brittleness than chromium alloys. Its also a somewhat tougher and more shock resistant at normal temperatures.

709M40 (En19) is a chrome-moly steel and 817M40 (En24) is a nickel-chrome-moly steel so both can have temper brittleness issues at higher temper ranges if heat treatment is not done well. Pretty much unheard of in practice for 709M40 on suitable duties, especially since Euro Norms rationalisation has reduced the chrome content a little, even at the highest tensile range. T is pretty much bullet proof. 817M40 (En24) has an unfortunate history of occasional, inexplicable, brittle fracture even in T condition. That alloy is, and always has been, known to be sensitive to less than precise control of heat treatment conditions so best reserved for applications that need it. Not purchased on the "Its more expensive so it must be better." basis.

What you are really buying with these three different steels is the maximum diameter at which a given tensile strength range can be reached. 605M36 (En16) manages 63 mm diameter at T, maximum practical is V at 19 mm diameter. 709M40 (En19) goes out to 100 mm diameter at T and can make W at 19 mm. 817M40 (En24) hits 250 mm diameter at T and 29 mm at W.

Can't see any point in paying extra for properties at a size much larger than I plan to use.

Its worth remembering that the Griffith crack length at which catastrophic failure occurs gets shorter as the tensile range gets higher. There is a double whammy in that steels capable of higher tensile ranges in larger sections tend to have shorter crack lengths too. Generally no great worry up to T condition but beyond that its important to pay proper attention to such things.

As Mike says sharp edges and other stress raisers can cause things to break even when the official loads are well within limits. Motorcycle forks are surprisingly flexi. Even the hefty racer breed.

Always a good idea to avoid seriously low temperatures too. Below -50°C or so unfortunate things start happening. I may be a 603M36 T fan boy but no way am I taking it to deepest Antartica winter as it seriously doesn't like getting really cold.

Clive

Edited By Clive Foster on 30/08/2021 22:40:47

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