A solution to NOT drill your track forks and have a normal front brake nonetheless

A star nut isn't the best of both worlds...an expanding wedge is, and i don't mean a quill style wedge.

The types used for carbon steerers make the most sense as they expand evenly all the way round unlike a stem style wedge quill, but they also allow tensioning against the base of the fork like a star nut whilst still allowing complete removal without resorting to hammers and scoring the inside of the steerer.

True. That might be interesting as well.

But keep in mind that the ones you mean do not 'cut' themselves into the material (which is why they are suitable for carbon), therefore are not equally strong.

The cutting and scoring isn't a problem at all if it's a steel steerer, aluminium is a different story, yes.

Star nuts may dig into the steerer, but they also place all the load on a much smaller area.
Don't underestimate the forces and vibration that heavy braking will place on each edge of each star nut fin.
Not to mention the threads of the securing bolt, which will only be holding by a smaller number of the threads an expanding wedge bolt will.

something like this one allows a huge surface area for both grip, and support...

But also, don't forget that pretty much ALL aftermarket wedges AND starnuts will be the wrong size, as the base of most steerers on older track bikes will have smaller internal diameters to the top of the steerer.
Some cast crowns have very little space inside, which again means that the braking force stress will need something with higher strength inside than starnuts.

IMO of course. :]

you may also find that in some forks, the diameter internally will go from very small at the crown to bigger only a little higher up.

This means if you hammer your double star nut through the small entry hole it may then be loose higher up right where it needs to grip.

Well interestingly we all seem to agree this is a marvelous idea. Now we're just fine tuning the fitting.

Anyone ever had 2 brakes on a front wheel..? one in front of the fork and one behind..?

When I lived in Vancouver with the constant rain, I thought it might help...

Star nuts may dig into the steerer, but they also place all the load on a much smaller area.
Don't underestimate the forces and vibration that heavy braking will place on each edge of each star nut fin.

As said, those forces would be redirected into a vertical pull at the starnut by making use of a short 'stem' that sinks into the steerer tube snugly.

Not to mention the threads of the securing bolt, which will only be holding by a smaller number of the threads an expanding wedge bolt will.

Anyway, steel bolt/thread combinations of >= M6 and a thread length of 10mm are nothing to worry about in this case I guess.

But also, don't forget that pretty much ALL aftermarket wedges AND starnuts will be the wrong size, as the base of most steerers on older track bikes will have smaller internal diameters to the top of the steerer.
Some cast crowns have very little space inside, which again means that the braking force stress will need something with higher strength inside than starnuts.

IMO of course. :]

That *is *a good point. The advantage of starnuts is here that they do not have to fit exactly as they can bend a bit, and some nice hammer strokes should get them in.
This diameter is more an issue with regard to the "stem" piece outlined above.
Either this stem is designed slightly conical, or it might be worth finding out if this diameter is about the same everywhere or inside what range it differs.

jetski

you may also find that in some forks, the diameter internally will go from very small at the crown to bigger only a little higher up.

This means if you hammer your double star nut through the small entry hole it may then be loose higher up right where it needs to grip.

Depends on the steel, as far as I know starnuts are made of a kind of spring steel, so should not be loose then.

Could we open a separate forks-lower-hole-measure thread? Everyone, please participate.

The forces due to braking would not be "redirected into a vertical pull".. Braking would put the star nut or whatever holding mechanism under shear load, not tensile. Maximizing surface area at the interface and mass at the joint is probably most optimal, try to minimize potential stress concentrations. That's not to say a star nut wouldn't do the job!

I think the tensile load wouldn't actually be very much.

can i get a picture of the fork that's on?

Designed for a frame which I don't have anymore.

...the base of most steerers on older track bikes will have smaller internal diameters to the top of the steerer...

It does not fit all steering tubes.

The angle may look off as I haven't tightened the clamp.

you sold the raleigh?

The last problem is simply clearance as others have mentioned.

A lot of track forks have very tight clearance.
In order to allow tyre clearance, the plate will need to be pretty thin, which increases flex.
A front brake can exert a lot of force, which will flex this plate and give poorer braking power.

This can be helped by keeping the plate as close to the crown as possible obviously, but again, there are several types of crown with differing widths, which means you'll need to allow for the widest.

There may also be an issue with the plate 'rotating' slightly under the crown.

Not all brakes pull evenly on both sides, either due to spring tension or poor setup, or wonky wheels, or uneven pad wear etc. Again the braking force and vibrations due to flex in the plate could possibly cause some slight rotation and hence brake rub.
Slight rotation back n forth could lead to loosening.

Just trying to cover all eventualities. :]
This could again depend on the shape of the front of the fork crown.

this is one of the few debates/discussions on this forum which has not descended into name calling... a nice change

Magnus, you are clearly dead-set that your idea is the best.
However, you have missed the point that the SFN is designed purely to offer a temporary and rudimentary anchor for preloading headset bearings. Once you fit a stem correctly the star nut/top cap arrangement becomes largely redundant.

Ed "uncle bulgaria" scoble's idea is better in my opinion and tynan's points are completely valid.

The forces due to braking would not be "redirected into a vertical pull".. Braking would put the star nut or whatever holding mechanism under shear load, not tensile. Maximizing surface area at the interface and mass at the joint is probably most optimal, try to minimize potential stress concentrations. That's not to say a star nut wouldn't do the job!

I think the tensile load wouldn't actually be very much.

ottbot, see above, if there's a bit of a stem fitting into the steerer snugly, then there is no other movement possible for the whole thing but up/down the steerer tube, therefore the force is actually redirected into a more or less vertical pull.

In the end, those carbon-suitable wedges will probably work as well, but might be not as slip-out proof as the starnut, and it needs to be checked if they might cause more problems than the starnut due to the variations in diameter at different track forks bottom holes.

The last problem is simply clearance as others have mentioned.

A lot of track forks have very tight clearance.
In order to allow tyre clearance, the plate will need to be pretty thin, which increases flex.
A front brake can exert a lot of force, which will flex this plate and give poorer braking power.

This can be helped by keeping the plate as close to the crown as possible obviously, but again, there are several types of crown with differing widths, which means you'll need to allow for the widest.

No worries, I have a solution for that which I will show later in the evening. Zero clearance.

There may also be an issue with the plate 'rotating' slightly under the crown.

Not all brakes pull evenly on both sides, either due to spring tension or poor setup, or wonky wheels, or uneven pad wear etc. Again the braking force and vibrations due to flex in the plate could possibly cause some slight rotation and hence brake rub.
Slight rotation back n forth could lead to loosening.

Just trying to cover all eventualities. :]
This could again depend on the shape of the front of the fork crown.

Even though it's not an actual problem, it will be resolved in the next design as well.

Magnus, you are clearly dead-set that your idea is the best.
However, you have missed the point that the SFN is designed purely to offer a temporary and rudimentary anchor for preloading headset bearings. Once you fit a stem correctly the star nut/top cap arrangement becomes largely redundant.

Ed "uncle bulgaria" scoble's idea is better in my opinion and tynan's points are completely valid.

RPM, I am not "dead-set" at all, I pay attention to every comment made and reply adequately. I would appreciate if you would read all my comments first. I already admitted that dmczone's mate's short stem addition to the hanger will improve the design, of course. But, any solution based on a normal quill stem (Ed) does not tighten the piece against the forks, and is therefore not suitable.
Regarding tynan's points, see my reply to him and to ottbot, above.

jetski

I would appreciate if you would read all my comments first.

jetski

I did, thanks.

ottbot, see above, if there's a bit of a stem fitting into the steerer snugly, then there is no other movement possible for the whole thing but up/down the steerer tube, therefore the force is actually redirected into a more or less vertical pull.

There is no redirection of force. The force will remain acting in the direction off pull, it will not go around corners if you know what I mean.

The force will remain acting in the direction off pull, it will not go around corners if you know what I mean.

The force isn't what it used to be. :[

There is no redirection of force. The force will remain acting in the direction off pull, it will not go around corners if you know what I mean.

tynan, "if there's a bit of a stem fitting into the steerer snugly, then there is no other movement possible for the whole thing but up/down the steerer tube"

Maybe it's a problem with my vocabulary, but it can't be too mysterious to understand what I mean? Imagine: tube width: say constantly 22mm, 'stem' length: say 45mm, 'stem' width: say 21.8mm, bolt length: say 60mm, 10mm high starnut at the end of that bolt.

Come on, how on earth would the starnut experience a relevant amount of shear force in this setup?

EDIT: in the end, the carbon-suitable ahead expander will probably do the trick sufficiently, so we should stop worrying about the "expander or starnut" question as it is something that everyone can chose afterwards, it's not directly part of the actual design anyway.

It would be more interesting how far the variations between classic steel track forks are. (hole diameter, diameter constancy and radius of the lower fork crown arc). For example, I found one expander that varies between 20,5mm to 25,7mm which is quite much and should be sufficient for most forks?

Could anyone measure their lower track forks hole, please? Thanks.

jetski

"*if there's a bit of a stem fitting into the steerer snugly, then there is no other movement possible for the whole thing but up/down the steerer tube"

Yes, but the idea that force is 'redirected' is wrong, putting a piece of 'stem fitting' into the steerer will not 'redirect' the force 'into a more or less vertical pull'.

Come on, [I]how on earth* would the starnut experience a relevant amount of shear force in this setup?

I don't think anyone has said it will.

by the way, I just measured my own forks: 19mm hole down there, really wondering now if this is constant up to a certain point (?) and then suddenly stepping to 22.2?

by the way, I just measured my own forks: 19mm hole down there, really wondering now if this is constant up to a certain point (?) and then suddenly stepping to 22.2?

Fork knows ?

Sorry about that, I'll get my coat.

Might be an idea to just make one and try it and put the theory into practice?

As each set of forks is going to be different at the bottom then it is not a concept that can be generally applied and each fork would need it's own dedicated design so making it to work with your fork and your fork only should be the aim maybe?

Might be an idea to just make one and try it and put the theory into practice?

As each set of forks is going to be different at the bottom then it is not a concept that can be generally applied and each fork would need it's own dedicated design so making it to work with your fork and your fork only should be the aim maybe?

A single adjustable expander would work for most steerers.

I've tried a couple of those carbon expanders on alu forks, which I thought I'd try before getting my LBS to fit a SFN, and none of them managed to stay in position (with little load on the top cap). So from experience I'd be weary to use one on a braking system...

Fork knows ?

Couldn't measure myself (I'm abroad atm), girlfriend had to do it, so I got no exact info.

So, still no clue about the details of my fork's 19mm to 22.2mm transition.

I've tried a couple of those carbon expanders on alu forks, which I thought I'd try before getting my LBS to fit a SFN, and none of them managed to stay in position (with little load on the top cap). So from experience I'd be weary to use one on a braking system...

wow - the first starnut supporter :-)