surly track hub to BMX spacing??

Anyone know if you can drop the 120mm O.L.D. on a Surly track hub down to 110mm O.L.D. for a trailer bike frame (BMX)?

The kid needs to do some spinning!

Thanks,
davedbk

 

Flip-flop == no
Single Sided == maybe (well, probably not)

Can you respace the dropouts to 120mm?

 

You could stop the rear cassette from coasting by tying it to the wheel. Try weaving a heavy-weight shoe string or a toe-strap in between the "spokes" of the cassette and the actual wheel spokes. I probably won't work all that well, but try it.

I've used this technique on mtn bike rides: when a freehub-body blows out, and the cassette spins freely in both directions, you can't pedal forward anymore. This has happened to older Hugi 240 rear hubs. We've been forced to tie the cassette to the wheel with a toe-clip-strap or else try and "scooter" a bike 20 miles out of the desert.

Ugg!

Good luck,

bama
http://baphometcycles.com

 

Good tip ...

Okay, it's too bad you apparently didn't know how easy it would be to service your Hugi 240 hub in-the-field ... it's true that you don't need tools to work on it.

I presume that grit infiltrated between the Freehub body & the Hub shell, itself ...

You probably just needed to rinse the dirt away from the Star Ratchet's reciprocating ring and then reassemble.

 

Apparently you didn't know how often the pauls and freehub-body shatter . . .

If you don't have anything nice to say . . .

 

FYI. There are no pawls, per se, in a Hugi 240 hub ...

Regardless, I did NOT know that the Star Ratchet mechanism could shatter ...

Your bad luck, apparently.

 

Surly tech said it couldn't be done and gave me the same suggestion, respace the dropouts.


What everyone's favourite method for spreading chain stays?

 

Thanks for the suggestion. How many miles do you get out of a shoestring?

I shall leave my findings, unless it last so long I forget all about this thread.

 

If your frame is steel, then you just need to use the brute force imparted by your upper body strength -- grab a dropout in each hand ... pull apart with whatever you estimate to be 30 lbs of force ... measure & repeat. DO NOT use any additional leverage than you can supply by your lonesome.

Align the dropouts by using EITHER a large adjustable wrench for leverage OR a medium pipe wrench whose jaws are sandwiched with a couple of small scraps of plywood (or, equivalent). Steel is SOFT, so only exert whatever you imagine to be 5 lbs of force.

If the frame is not steel, then forget it.

BUT, why not just buy a 28h or 36h BMX hub OR are you committed to a 32h rim?

 

My scanning of the usual online suppliers revealed no fixed gear threaded bmx hubs. Do you know of any?

 

Well, SOMEONE came up with the very clever (IMO) modification of a FRONT DISC HUB whereby he simply bolted the cog-of-choice to the 6-bolt disc mount ...

So, choose-and-mount a cog ... adjust the left-right offset with spacers (I think that EITHER an "old" Magura front disc hub OR Shimano front disc hub which uses loose bearings will be easier to work with because you'll want to insert a longer-or-solid axle) to determine your chainline ... lace up the rim ... VOILA!

OTHERWISE, use a lockring from a standard English threaded BB ... I would insert a 'washer' made from a laundry detergent bottle, or equivalent, between the cog & the lock ring.

 

I first tried 15lb fishing line. My son (70lb) got on. He got off. He got on and it snapped. Not 1 metre. (He stands on the pedal to swing his other leg over.)

 

Okay, so now we know that the STRING THEORY isn't viable ...

Again, using an English threaded BB lockring with a Track Cog is a commonly used method to go Fixie & is certainly easy enough to implement ... remember to use a Washer to "lock" the lockring ...

BTW. The common suggestion is to use Loctite or Solder(!?!), but I think a Washer would be a better choice.
​

If you don't want to cut a Washer from a detergent bottle, then you can certainly use as BB spacer.

 

I've got the BB lockring.

Re. the washer - are you saying cut a disc from the side of a detergent bottle or from the base of the lid? i.e. 0.5mm thick disc or 2mm thick ring?

 

I suggest you use the plastic from the jug portion ...

Making a Washer from the cap would require too much effort!

The plastic jug is just the easiest material which should work ... you can certainly can make the Washer from almost any material except a paper-based product ...

For example, if you have an old spoke or wire coat hanger, you could just bend a DIY split O-ring which you would be sandwiched by the Cog & BB lockring.
​

 

re the track sprocket...

I bought a 13T - I want my son to do some spinning, not a whole heap.

It has a shoulder on one side. I imagine you install the sprocket with the shoulder on whichever side gives you the best chainline.... or is there a regular side?

I hope it isn't critcal because the BB lockring is 45.9mm in diameter versus the sprocket valley diameter being approx. 45.1mm. If the BB lockring sits against the flat side of the sprocket (with thin washer between) the chain sideplates will hit the BB lockring.

So... is it critical which way the track sprocket installed?

 

HMmmm. If there is an integrated shoulder which makes the cog 5mm thick, then it should probably be on the spoke side UNLESS you can mount it shoulder side out and not have the chain grind against the spokes ... that is, you would want to mount a spare cassette cog spacer (as an example) on the hub before you thread the cog on the hub if you wanted to mount the cog with the shoulder side on the outside.

As far as the BB lockring diameter ... there is no standard circumference ... some are larger than others [the one you have is certainly one of the larger ones ... I did have one on a French BB which was probably about the same size as the one you have, maybe it was 0.1mm larger -- I wish I still had it!].

I randomly grabbed (i.e., it was available) one of the larger BB lockrings (it's steel) which I have, and it is only 4.5 cm in diameter.

An alloy lockring from an OMAS BB is 4.4 cm in diamter.

The alloy BB lockring from the first generation Dura Ace & XTR Octalink BBs is even smaller -- about 3.95 cm.
​

If the size differential of the lockring is either an impediment to the chain OR cosmetically unappealing, then you can reduce the size of the diameter if you have a 'standard' size (e.g., 4.5") hand grinder [mount the lockring on the hub with some spacers instead of the cog if you want to reduce its diameter with a hand grinder] and some patience & normal hand-eye coordination ...

ONE THING you might want to consider doing is to grind ~1.0 cm FLATS on your current BB lockring which are offset by 180º from each other & 90º from the notches in the lockring ... doing so will give you the option of using a medium-to-large adjustable wrench instead of a lockring tool.

BTW. I think that if your 13t cog uses a 3/16" (vs. 1/8") Road chain then it may actually be a threaded UNIGLIDE cog from a vintage 7-speed Shimano cassette ... maybe not ... not that it matters, either way.

 

....progress update

I had the freewheel removed free of charge - thankyou Elite Cycles Perth - and threaded on the track sprocket. The chain clears the spokes when the teeth are on the inside (shoulder outside). That is good news.

... but my Roselli track sprocket is 8.something mm wide (about 11/32"), leaving me with two threads for the BB lockring and washer - not enough. (it is afterall a cheap non-forged alloy hub).

What is the normal width of a 13 - 14 tooth track sprocket?

 

I don't know ...

If you look at the threaded portion of a Track hub onto which a Track cog is threaded you will see that it is only (about) 5mm wide ...

So, there really isn't any reason for the cog to be more than 5.1mm wide ...

And, I guess that 'I' would machine/file/(grind?!?) the excess width away so that the cog is about 5mm thick ...

This is not that hard to do ...

Several years ago I took an 11t Campagnolo cog for/(from) an 8-speed (MTB) cassette & changed its thickness to that of a 9-speed cassette's 12t cog ...

I also narrowed one for a 10-speed cassette.
​

You just need a moderately steady hand, a normal size vise-grip, a (hand) grinder, and a good Flat Bastard file ...

Mark/tape the cog ... you will remove about 90% of what you want with the grinder by gently touching the SHOULDER PORTION of the cog against the grinding wheel ... then, dress/face the rest with a GOOD (~10", including the tail) Flat File.

Done.

It probably won't take you more than 15 minutes if you use both a hand grinder & file.
​

Since you probably aren't going to be mounting the cog on a Track hub, you can remove as much of the shoulder as you want ... and/or, if you were to (inadvertently) make the cog narrower than 5mm, then you would just use a spacer if you were to mount the cog on a Track hub at some future point in time.

BTW. I think that if the face of the shoulder isn't perfectly square, then you may actually not need a washer (I would use one, anyway) ... but, if you decide to mount the cog with the shoulder facing the spokes, then you would want to make the shoulder as square a possible.

 

Does the bike have a front brake? Then don't install a lockring at all. Most track guys don't use a lockring either. From Clark Sheehan, Jonathon Vaughters,among others.