Innovators, a better part is needed!

[trapdoor2]

This weekend I upgraded my shift/brake cabling all around. Much happiness with that.

However, one issue I have been having isn't completely solved to my satisfaction. The FD shifting is better (since I replaced the kinked cable/housing) but that little sheave up front that routes the cable 180 deg. is on my list for improvement.

1. It is already distorted.
2. It doesn't fit perfectly on its shaft/bolt.
3. It doesn't account for the entrance or departure angle of the cable (apart from being wobbly).

I'm thinking that we need a nice, high-zoot ball-bearing inserted into a black delrin sheave. It needs to have a spiral/angled groove around the perimeter of the sheave for the shift cable to deal with the few degrees of entrance and departure angles...and it needs to fit the bolt properly.

[\wish list]

Any takers?

 

[RojoRacing]

picture?

 

[trapdoor2]

picture?

I'll see if I can rig up some lighting to get a pic of the current install. I'll be working up a model in PTC Creo this week. Drawing up the sheave will be easy, I'll have to ask one of our real designers how to do the cable-groove though.
Biggest problem is getting to the damn thing. Can't get a hex wrench on the bolt as the chain-ring is in the way. Ah well, I have been wanting to mess around with my chain-ring position anyway...

 

[trapdoor2]

Ok, here are a couple of pix. First pic is a view down from the top of the bike. You can see that the sheave is tilted and that it does not take up the full width of the shoulder bolt. You can also see the angularity of the cable entering the sheave.


Then, we have a view from the side...underside, that is. I assume the threads on this (L/H) side are there for some purpose.

 

[RojoRacing]

Oh so your just dissatisfied with the quality of the design and not what actually is going on. So you'd be happier with something along the quality of the Rollamajig I made last month right? What CruzBike is using there is a simple and maybe poorly executed bushing pulley system. I proper brass bushing would yield near roller bearing smoothness and still be on the cheap side. Yeah I too think the oem setup is a bit hokey but it seems to move easy enough to not cause drag on my bike. I don't recall mine looking so angled but I'll double check tonight. Maybe your was just welded on a little off.

 

[trapdoor2]

Oh so your just dissatisfied with the quality of the design and not what actually is going on. So you'd be happier with something along the quality of the Rollamajig I made last month right? What CruzBike is using there is a simple and maybe poorly executed bushing pulley system. I proper brass bushing would yield near roller bearing smoothness and still be on the cheap side. Yeah I too think the oem setup is a bit hokey but it seems to move easy enough to not cause drag on my bike. I don't recall mine looking so angled but I'll double check tonight. Maybe your was just welded on a little off.

I don't know about "dissatisfied". The system works...but it bears improvement. The pix don't show how distorted the sheave is on my bike. I can't fit my phone in to take a pic of the distortion...but the sheave is actually warping under the load (it isn't "a lot" but it is there). It needs to be wider where the shaft goes thru...perhaps using a sealed bearing or at least a proper brass bushing.
There are some geometry issues that could be better dealt with as well. The cable stop isn't in the same plane as the sheave and then the FD lever is in a different plane. Optimum would be to have the cable depart the stop and enter the pulley with no angularity...not sure that is possible without major work. However, I think that a specially designed pulley might get us closer to optimum. Of course, this thing doesn't rotate thru more than a dozen degrees or so...
I've got some measuring to do before I crank up the CAD program. Just sort of thinking out loud at the moment.

 

[Dave Arnold]

Marc,

Do you have your FD cable routed coming around the outside (chainring side) of the pinch bolt or starting on the inside and wrapping around to the outside. I moved mine from the inside to the outside and that seemed to help with the pulley alignment. Regarding the design of the pulley: If you think about how a RD cable is routed on a DF bike, usually the cable runs over a plastic guide on the bottom of the BB shell. Essentially it's just there to offer a smooth surface for the cable to slide over--the same thing the plastic pulley does but the pulley might actually work a little better then the typical DF guide.

 

[McWheels]

http://www.ebay.com/itm/3-Speed-Stu...095792?hash=item41b0dc3530:g:q4cAAOxybxlTlzBm

?

 

[RojoRacing]

Ok I fixed this today with a plastic pulley on a smooth ball bearing. If you remember my Rojomajig project for eliminating the large cable housing loop for the RD when using road specific RDs. Well today I installed all new cables and housing without my Rojomajig because I'm trying something else. Anyways I robbed the pulley from the jig and used it to replace the stock cruzbike bushing pulley. The bearing ID in the pulley is 0.005 too small for the 5mm bolt used by cruzbike but I was able to carefully force the bolt through the bearing by tapping it with a hammer and then I cleaned up the slightly marred threads with a M5x0.8 threading die. The new pulley lines good and there's a noticeable smoothness over the stock setup. $10 for the Pulley with bearing installed and probably another $5-10 for a threading die to fix the bolt threads after pressing it through the bearing.

Here's the pulley part #
http://www.mcmaster.com/#3434T14

 

[trapdoor2]

Leave it to McMaster-Carr to have the right item. I love their website...considering that back before PCs, the McMaster catalog weighed about as much as I did...and was a b*tch to find anything in.
I need a couple of other small parts from them, so I'll add that one to the list. Thanks Jason!

 

[Dave Arnold]

Hello all, just a warning: I just bought the part from McMaster-Carr. During the checkout process I was never told about shipping charges. I later read that they charge what UPS actually charges them. I figured what could a part the weight of a quarter cost anyway, so I ordered it. Today I received an updated receipt that showed the shipping charge of $7 for a $10 part.

 

[RojoRacing]

Hello all, just a warning: I just bought the part from McMaster-Carr. During the checkout process I was never told about shipping charges. I later read that they charge what UPS actually charges them. I figured what could a part the weight of a quarter cost anyway, so I ordered it. Today I received an updated receipt that showed the shipping charge of $7 for a $10 part.

UPS is not USPS, they don't have shipping options below $7 for anything that box shaped no matter how small.

If you think of the part as $17 with free shipping it may not hurt so much but yeah it sucks.

 

[Patineto]

Beautiful durable brass cable guide

Look for a Suntour roller cam brake, you get two of them and they last forever.