Track fork end slot dimensions?

Hunter said:

How deep should the slots be to allow sufficient adjustment for SS
purposes? How wide the slots? Does there need to be a particular
profile at the back of the slots to allow for the use of chaintugs? I
can, of course, just measure the axle width and guess on the depth, but
I didn't know if there were "magic numbers" that I should be aware of.

1) One-quarter inch per anticipated tooth difference (~6mm)
for sprocket changes over what you need to reasonably fit. Since
each full link removed or added moves the axle one-half inch
and you probably want the axle nuts to be fully supported
(with a floating washer you will be approaching 20mm), 30
millimetres is probably a safe minimum for slot depth.
2) Two to six mm
3) No, and chaintugs are a useless prophylactic

Typically rear axles are ten millimetre diametre.

My Yokota track bicycle has the following dimensions for the
slot in the fork ends:
45mm by 10mm by 3mm.

On 1 Aug 2006 10:39:00 -0700, "Franklin" <[email hidden]>

Quoted message said:

Hunter said:

How deep should the slots be to allow sufficient adjustment for SS
purposes? How wide the slots? Does there need to be a particular
profile at the back of the slots to allow for the use of chaintugs? I
can, of course, just measure the axle width and guess on the depth, but
I didn't know if there were "magic numbers" that I should be aware of.

1) One-quarter inch per anticipated tooth difference (~6mm)
for sprocket changes over what you need to reasonably fit. Since
each full link removed or added moves the axle one-half inch
and you probably want the axle nuts to be fully supported
(with a floating washer you will be approaching 20mm), 30
millimetres is probably a safe minimum for slot depth.
2) Two to six mm
3) No, and chaintugs are a useless prophylactic

Typically rear axles are ten millimetre diametre.

My Yokota track bicycle has the following dimensions for the
slot in the fork ends:
45mm by 10mm by 3mm.

1: It's one eighth per tooth (chain goes halfway round a circumference
increased by 1/2", and this extra 1/4" of chain is spread between the
upper and lower runs. To ensure you can find a chain length to work
with any gear, you need 1/2" of movement without the tracknuts
overhanging the back of the slot, so the bare minimum slot length is
27.7 for a 10m axle with 20mm captive washers on the track nuts.

2: Thicker is generally regarded as better, less than 4mm steel or 6mm
aluminium is asking for a bent dropout the first time you pull the
wheel forward with you starting effort, which brings us to...

3: Chain tugs are useful, but most types are fairly unfussy about the
shape of your forks ends if they're simple flat plates. I'll qualify
that by saying chain tugs are unlikely to be essential if you use a
big enough chainring, but for hill climbs where a small (42t) ring and
a big effort combine to give very high chain tension, it's fairly easy
to pull the wheel. They also make tension adjustment easy,
particularly if you need to take the wheel out frequently for
transport.

FWIW, the slots on my steel Fort are 35mm long and 7,5mm thick

Kinky Cowboy*

*Batteries not included
May contain traces of nuts
Your milage may vary

Thanks to you both. The plates are 6mm.

I'm in Colorado, and most Front Range parks have stiff opening ascents
that will require low gearing, and therefore chaintugs sound wise.

I've been questioning the viability of fun singlespeeding at all given
the typical trail profiles here. I'm not the worst climber around, and
can middle ring the majority of the climbs here, but I don't think I
can do them in, say, a 32/18.

Hunter said:

Thanks to you both. The plates are 6mm.

I'm in Colorado, and most Front Range parks have stiff opening ascents
that will require low gearing, and therefore chaintugs sound wise.

I've never used them, nor needed them, and I have used quite low gears on
my fixed gear bike from time to time.

Quoted message said:

I've been questioning the viability of fun singlespeeding at all given
the typical trail profiles here. I'm not the worst climber around, and
can middle ring the majority of the climbs here, but I don't think I can
do them in, say, a 32/18.

You'd be surprised what you can climb with a gear like that. That is
pretty low for a fixie.

--

David L. Johnson

__o | It is a scientifically proven fact that a mid life crisis can
_`\(,_ | only be cured by something racy and Italian. Bianchis and
(_)/ (_) | Colnagos are a lot cheaper than Maserattis and Ferraris. --
Glenn Davies

Kinky Cowboy said:

1: It's one eighth per tooth (chain goes halfway round a circumference
increased by 1/2", and this extra 1/4" of chain is spread between the
upper and lower runs.

You are correct

Except

Quoted message said:

From a 50:15 to a 47:15 I measured a movement

more than slightly greater than three-eighths of
one inch. Less than one-thirty-second less than
one-half inch. I would assume that the dif'rence
in included angles could account for this. Another
set of possibilities would be sprocket eccentricity,
chain tension variance, my inability to measure
accurately, local gravitational lensing effects, not
using genuine shimano replacement parts, a wo-
oden ruler being not UCI legal.

I would assume that the actual sprocket sizes
would affect this as well (or at least relative to
chain pitch).

Axle tugs increase the difficulty of unshipping
the chain for wheel removal, if that makes any
difference. My experience of using a 39:16 gear
on forward-facing drop-outs with quick-release
(170mm cranks) was altogether without disaster.

Kinky Cowboy said:

On 1 Aug 2006 10:39:00 -0700, "Franklin" <[email hidden]>

Quoted message said:

Hunter wrote:

<snip> Does there need to be a particular

Quoted message said:

Quoted message said:

Quoted message said:

profile at the back of the slots to allow for the use of chaintugs?

<snip>

Quoted message said:

3: Chain tugs are useful, but most types are fairly unfussy about the
shape of your forks ends if they're simple flat plates. I'll qualify
that by saying chain tugs are unlikely to be essential if you use a
big enough chainring, but for hill climbs where a small (42t) ring and
a big effort combine to give very high chain tension, it's fairly easy
to pull the wheel. They also make tension adjustment easy,
particularly if you need to take the wheel out frequently for
transport.

FWIW, the slots on my steel Fort are 35mm long and 7,5mm thick

Kinky Cowboy*

*Batteries not included
May contain traces of nuts
Your milage may vary

Just regarding the shape, it's worth ensuring that the a line drawn
touching the two "back end" points of the drop out (the two spots
against which "T" piece of the chain tug will sit) is perpendicular the
line of the slot itself. Hope that makes sense, I may not have
explained it too clearly...

More important than the chain tugs themselves are to use good quality
track nuts (if using a solid axel), or a good quality QR skewer with a
steel shaft (not titanium - it's commonly thought that it stretches too
much in this application).

You shouldn't be dependent on the tugs to hold the wheel back against
the chain, but I do find them useful when setting the chain tension and
aligning the wheel in the frame.

regards,

bookieb.