Group buy?... Doctor Bass Torque arms for NuVinci N171B

[LI-ghtcycle]

I have spoken to the great Doc, and asked him about the possibility of some torque arms made specifically for those of us using the NuVinci N171B & Developers kit (2nd generation 350% NuVinci Hubs) and possibly the new N360 (not sure of the dimensions of it's axles, I'll call Fallbrook Tech in the morning).

Anyway, Doc says we need to do a minimum production run of 12 sets and I am able to swing that on my own, but I don't need that many yet, so I am wondering who else would be interested in some?

Not exactly sure how much he will need per set for this first smaller production run (the larger the run, the cheaper the TA's, the smaller, the more expensive they are for him to get made) so I will defer to the Doc on what he feels is the best price for these.

These will have a 12mm axle with 10mm flat TA's for the freewheel side and 10mm axle with 8mm flat TA's for the brake side that will be mounted with the same high strength epoxy that Doc uses for his larger one as described here at his selling thread:

http://endless-sphere.com/forums/viewtopic.php?f=31&t=29129&hilit=torque+arms

Anyhow, let me know if any of you using the N171B NuVinci or the recent $150.00 Developer's kit specials (this is the same N171B hub with a electronic shifter instead of manual) and want to beef up your drop outs with one of if not THE best commercially available Torque Arms (these are designed for super E-Bikes putting out in excess of 5,000 Watts!! ) on the market for your new NuVinci project.

Thanks!

 

[StudEbiker]

I'm having a hard time understanding why you need torque arms with the Nuvinci. As it doesn't produce any torque on it's own, there would be no tendency to spin the axle.

 

[Rassy]

All IGH's have to be "fixed" in the dropouts just like a hub motor, because they will try to spin the axle in the opposite direction of the wheel spin. If the axle would spin easier than the wheel, then that is what would happen. Even if you go look at the ancient 3 speed bikes you will see that they have a torque arm strapped to the bike frame just like the old coaster brakes.

 

[LI-ghtcycle]

I'm having a hard time understanding why you need torque arms with the Nuvinci. As it doesn't produce any torque on it's own, there would be no tendency to spin the axle.

I would disagree, I have caused my left side (brake side) axle, the 10mm side to nearly spin in a steel 1/4 inch torque plate under nothing more than leg power with a heavy touring bike with full camping gear last August on my trip to the beach. :wink:

Given the fact that the highest estimates of power put out by my legs some gave me for the grades I climbed (near 20% for about 2 blocks in Astoria Oregon) of about 400 Watts burst, I would absolutely recommend that ANYONE using a NuVinci or any other IGH of any kind to remember to beef up the drop-outs or where ever you have your IGH anchored, because in a very real sense, there will be not only the same power applied to the drop-outs as a hub motor, but it can in fact be multiplied by the stage of reduction from motor to hub.

For example, say you have a 2000 Watt load on your drop outs with a hub motor, and it produces X torque.

Now take that same hub motor, give it a 6 to one reduction and now put that same 2000 Watts at the motor, now given a huge mechanical advantage (envision the 6:1 reduction as a long pry bar) and now you are multiplying the same power considerably!

I am not a math whiz, and I can't make a diagram or write up a formula to explain why this is, however, I know from experience it absolutely works this way, and I have the thread pattern of the 10mm axle's threads imbedded into the torque plate to prove it.

 

[StudEbiker]

This is good info to have and now that it is explained it makes perfect sense to me. I'll definitely be looking at those torque arms to see if they are practical for use on the Bike E.

 

[LI-ghtcycle]

Good deal, hopefully we can get enough of other people using the NuVinci hubs including the Dev Kit version to join in and get a good amount of them going.

I am willing to pay for at least half of a production run myself, but the more the merrier!

How is your Dev kit treating you these days StudE? Hopefully it's not giving you as much trouble as before?

 

[amberwolf]

Torque arms for the NV is an interesting thought...but I don't think I'll have room for their thickness on mine, because of the way the swingarm pivot bearings have to fit over the axle along with the nuts and whatnot, plus the shifting mechanism hardware.

The clamping "dropouts" will have to do the job for me.

 

[StudEbiker]

How is your Dev kit treating you these days StudE? Hopefully it's not giving you as much trouble as before?

Testing has stopped as I am waiting on a Headway battery to arrive I bought from Neptronix. I hope it comes tomorrow and I can resume testing this weekend hopefully.

 

[Glenn_M]

Interested but will need price + postage to Australia to confirm. One set only needed.

Glenn

 

[Burtie]

Because the hub both multiplies and divides torque (low or high gear), there will be an associated torque reaction on the axle which needs to be contained. This reaction can be in either direction depending if the hub gear ratio is set >1 or <1 .

The supplied anti rotation washers dont look very strong. depending how much power you intend to run, it would suggest using something better.

On my NV 171 hub, the flats on the axles are vertical on one end, but horizontal on the other end.

If you want to use the flats on both ends of the axle, at least one of the torque plates will need to be removable, or it will be difficult (or impossible)
to insert / remove the wheel.

I ended up making a couple of bolt on, clamping torque plates to do the job.



Burtie

 

[LI-ghtcycle]

Oh yes, very good point! On the brake side, the small diameter is horizontal while the freewheel side is vertical.

So in that case, perhaps the more reasonable solution is to have a Doc Bass style torque arm on the freewheel side, and a custom plate on the brake side.

I agree that for our application the supplied washers are not up to the task of 2000 Watt+ power, however, on the 12mm axle on the freewheel size, I have yet to have any trouble using just that, there is less space on this side available for a torque plate/arm, and I have used the supplied hardware with great success.

This would definitely change if I had sustained power above 2000 Watts, right now I have momentary spikes of 2500 Watts, but that is the absolute maximum I have seen according to my CA so far, and it has handled it fine. The highest sustained watts I generally use while climbing a steep hills is 1500 Watts, and when I have been forgetful and allowed the axle bolts to get loose, the worst that has happened is the NuVinci hub feels like it has gone into "neutral" and even though I have some forward propulsion still, it defaults to a very low "gear" (this has happened on two occasions due only to my not checking things as often as I should) and rather than spin out the torque plate/arms or drop outs, the hub slips internally.

A greater input than the designed maximum torque will result in an internal slip so there is a built-in safety measure to prevent damage, not sure how much of this is by design, but I can tell you with both the acorn nut on the brake side finger loose, and the locking nut on the freewheel/control pulley finger loose, the first thing that starts happening is the pulley begins to pop off.

Once I started to recognize this, I know immediately if things are slipping that I need only to check the axle nuts, and I am back on the road with no problems.

I love the fact that if you over-power the NuVinci or neglect to keep the axle tight that it doesn't just trash the hub, it just starts to slip, and with my torque plate on the brake side with the small 10mm axle, the torque plate is bolted to the frame through the fender and rack mounts, and never has given me any real trouble thus far.

I will see what the good Doc thinks about some form of bolt on plate for the brake side that will be a more generic design to allow use on most frames.

Thanks again for pointing that out Burtie!

 

[LI-ghtcycle]

Well, I have been thinking about something that would be a compromise between Doc's design, and a clamping drop-out for the NuVinci, and here is what I came up with so far:

The top half of this crude quick & dirty drawing would be glued to the frame just above the drop out, and this would be done in such a way as to compliment a Doc styled drop-out on the 12mm axle side.

One nice thing about this for the NuVinci is that you don't have to worry about the torque arms being glued on perfectly since your not going to have the same possibility of trapping the axle if they are misaligned since the small side has a removable clamping side to the TA.

What do you think?

 

[ejonesss]

sorry to bring up an old subject but i think there may be a problem with some frames because the axel is so short.

i found a way (i have not tested yet)

take some bunched flat slotted bars

http://www.hdsupplyhardwaresolutions.com//Products/ProductList.aspx?Type=T3&Cat=C19&SubCat=S59&Part=62451 and stack them (you may have to enlarge the rectangle like holes to fit the axel (have not tested yet)) and put them over the axel and clamp to the frame.

 

[Hosedragger]

Just adding this option. I used these torque arms on my Nuvinci N171 CVT hub and they worked great. Just had to cut a slot in the LH torque arm for the factory anti-spin washer to fit into since the LH side axle is small diameter.