Schlumpf hubs: general discussion

Unicycles and Equipment
2524

Not sure if this is the right thread for this specific question.
I want to build a wheel with a Schlumpf hub (100mm) and a 622 rim. The ERD is supposed to be 600mm (will check, once I have the rim). This ERD is virtually identical to the 29" Kris Holm Freeride rim (599.7mm), according to the UDC spoke length calculator.

Using UDC’s calculator I get spoke lengths of 279mm and 281mm. Using four other calculators (Online Spoke Calculator for Hubmotors and Ebikes, Speichenlängen-Rechner, https://spokes-calculator.dtswiss.com/en/calculator, #1 Wheel Building SPOKE CALCULATOR Now Online | PROWHEELBUILDER | Prowheelbuilder.com) I get spoke lengths of 285mm and 287mm. This is considerably longer.
Thus my question to those who have built a Schlumpf wheel: Are the results from the UDC calculator for this specific hub really that far off? Maybe I did some miscalculations as far as the dishing offset is concerned (I got 11mm to the right side). I’m a bit puzzled since the the only calculator that is unicycle specific and has this particular hub in its data base seems to be so far off. You’d assume it should be the one with the correct values, but then there are four other calculators that all give a different result with a very small bias… :interrobang:
Has anybody built a wheel with the Schlumpf hub and the mentioned 29" KH Freeride rim (or another rim with 600mm ERD) and can confirm whether the UDC calculator was right or not?

(Edited for a small clarification)

2525

Well, I have successfully built a recent Schlumpf wheel (but with different rim and with the 125mm hub). You don’t need to go to a calculator web site - you can simply plug some numbers into a formula and paste that into a google search and it will do the calculation for you.

The formula (for a standard cross 3 lacing with 36 spokes) is:

L = sqrt(d^2 + r1^2 + r2^2 - 2*r1*r2*cos(pi/3)) - r3

However, if you have a different number of spokes than 36 (but assumed to be an even number, same count each side), then use the following formula:

L = sqrt(d^2 + r1^2 + r2^2 - 2*r1*r2*cos(4*pi*x/n)) - r3

here x is the number of crossings (e.g. 3) and n is the spoke count (e.g. 32).

the other symbols have the following meanings:

d = offset along from axle center to flange
r1 = flange radius to spoke hole midpoint
r2 = ERD/2
r3 = flange spoke hole radius

So, to explain these in more detail:

d assumes that the rim spoke holes on your 29er rim will be in a plane which intersects the axle at the midpoint between the 2 bearings (in your case 50mm from each bearing center). The actual hub flange on one side has an offset from the bearing of 10mm, so its offset from the center plane is 40mm. The other hub flange (disc side) has an offset of 16+16 = 32mm from the bearing, which means its offset from the center plane is 18mm. So, d will be 18 on the brake side and 40 on the non-brake side.

r1, I believe is 45.5mm, assuming that your hub flanges have a distance (on each flange) of 91mm between the centers of opposing spoke holes. You should check this on your actual hub.

r2 is 300mm, assuming the ERD is 600.

r3 is 1.1mm, assuming standard gauge spokes.

substituting these numbers we have 2 formulas (for 36 cross 3):

sqrt(18^2 + 45.5^2 + 300^2 - 2*45.5*300*cos(pi/3)) - 1.1 =
sqrt(40^2 + 45.5^2 + 300^2 - 2*45.5*300*cos(pi/3)) - 1.1 =

just copy and paste a formula into the google search bar to get an answer.
when I do it (using the above numbers, which you should check) I get:

279.5mm and 281.8mm which is much closer to the UDC numbers.

But if 32 spokes is assumed, we need to use the other equation with x=3 and n=32…

sqrt(18^2 + 45.5^2 + 300^2 - 2*45.5*300*cos(4*pi*3/32)) - 1.1 =
sqrt(40^2 + 45.5^2 + 300^2 - 2*45.5*300*cos(4*pi*3)/32) - 1.1 =

to get 285.2 and 287.4 which is closer to the other calculators.

Extremely minor inaccuracies can happen due to assumptions about the nipple, the exact center line of the spoke, the spoke tension stretch, and the ERD. Of these, the ERD is the biggest worry (do you trust the rim specifications, or do you measure, using your spokes?).

Spokes will stretch a bit under tension, but this is not much. If a bit too long, it is not critical if the rim has a double wall. If you are getting the spokes cut, you may be able to ask for the threaded section to be a tiny bit longer to minimize nipple threading issues.

Good luck with your build.

NOTE: I edited this post to cover the case of 32 or 36 hole rims, as I guess some people will choose the new option of a 32 hole hub which might give a greater range of bicycle rims to choose from.

3 Likes
2526

The key part is that the data for the hub is correct.

For the current disc hubs - 100mm I’m using these values:

IMG_3742
IMG_37421604×695 105 KB

Plugging this into my spoke length calculator with an ERD of 600- I get:

278.9 / 281.4 - always round this up! - so 279/282 - or you could just opt for 280/282

(it is paywalled so can’t share)

But you should probably check the ERD with the nipples you plan to use as sometimes the rim doesn’t factor this in - unless you’ve factored in it already.

Failing this just reach out to the rim manufacturer and ask again for clear ERD info - it might be related to there being a few versions of the Freeride rim.

Hope the build goes well! :star_struck::gear:

1 Like
2527

Thanks, @gocup and @mindbalance for your highly valued input. The baseline seems to be that the UDC calculator can be trusted for calculations for the Schlumpf hub. Will double check with gocup’s formula once I actually have the rim and have determined the ERD myself.
The strange thing is that the numbers I used seem to be the same that you guys used, except maybe for r3; according to UDC the flange hole diameter is 2.6mm, so radius is 1.3mm. But that is peanuts. I used the following numbers (hope Florian doesn’t mind me posting this:

Masse Schlumpf_900
Masse Schlumpf_900900×1084 165 KB

Everything in black is original, the colourful part is my contribution.

I’m still a bit puzzled, but I’m glad to know that the UDC calculator seems to be the one to trust most, and I can double check with the provided formula.

PS: Instead of 18 and 40mm offset I also tried 17 and 39mm, since the schematics of the calculators imply that they measure from the centre of the flange while Florian measures from the outside of the flange (I assumed the width of the flange to be 2mm). But that obviously doesn’t change a whole lot for the final spoke length.

2 Likes
2528

Finally found the issue …and it‘s a bit embarrassing. :flushed:
The UDC calculator always resets the spoke number to 36 when you change the hub or rim type. My guess is that this happened when I did the calculations, without me noticing it. When the spoke count is set to 32, the results are in the same ballpark as the results of the other calculators (maybe a tad shorter, will have to properly check).
Phew! :sweat_smile:

1 Like
2529

Ah ha… I edited my formula (in my post above) to account for the 32 spoke case. And of course, the results for 32 spokes then match the non UDC calculators. Once again, good luck with the wheel build!

2530

Thanks a lot, @gocup, I made an Excel Sheet with your equation (and I even get the same results, this time :grin:). The rim is already here, nipples should arrive next week. Then, I’ll be able to measure the ERD and see if the nominal 603mm (I ordered a different, sturdier rim than originally planned) are correct. The Schlumpf hub is ordered, too, but I have no idea when it’ll be delivered. In a reply to an enquiry of mine via e-mail, Florian wrote that the hub is available “short term”. I shall see. Exciting times :partying_face:.
The resulting lengths of your equation correspond to the decimal to those of the DT Swiss calculator, by the way, while the UDC calculator calculates 1mm shorter spoke lengths. Will have to see what length I’ll be able to order anyway.
An interesting addition is that the DT Swiss calculator factors in the desired spoke type (their own spokes only, of course) for the final length recommendation. A calculated length of 286.4mm gives a recommended length of 287mm for DT Competition (2/1.8/2) spokes, while a length of only 286mm is recommended when using DT Alpine III (2.34/1.8/2) spokes. I think I’ll go with Alpine III for the disk side and Competition for the non disk side, if I can source them.

2531

Some more observations - things start to get a bit tricky when you have to consider the actual physical spokes, nipples and rims (and hub). For example, longer brass nipples usually have a longer threading range allowing compensation for spokes not of the “perfect” length. It also seems that ERD is not as simple as it could be as it depends on the nipple and whether it is measured when the spoke tip aligns with the bottom of the screwdriver slot or the top of the nipple head (if that is possible - sometimes it can’t screw in that far). And some spokes have more thread than others. By the way the spoke length is always measured from the inside of the J bend. Spoke elongation under tension might be about 0.5mm, depending on the spoke, and also depending on the tension (more elongation on the brake rotor side, less on the non-rotor side). Spoke length is usually rounded down (not up) from the theoretical length to get the spoke size. When you get the hub, you will see another spoke dimension can be important - the length of the J part which goes into the hub flange. Note that the rotor side flange is thicker than the non-rotor side flange, and of course the spoke angles are different. There are 4 categories of spokes to consider - inner rotor side, outer rotor side, inner non-rotor side, and outer non-rotor side. One or more of these might benefit from having spoke washers under the spoke head at the flange (this has been discussed on the forum somewhere). I guess all this planning hassle contributes to the feeling of accomplishment when the wheel is built. (The actual lacing up of the wheel is the easy part!)

3 Likes
2532

That‘s why I need to wait for the nipples to arrive. They‘ll be aluminium Squorx nipples. I chose them for two reasons: They’ll be easier to tighten from the back, so the black anodising won’t be damaged. And for the only wheel set that I’ve built myself (for a touring b!ke, many years ago) I used simple, reliable stuff: DT Champion spokes and ordinary brass nipples. This new wheel shall be a bit fancier.

Oh, I thought they were measured from the central line. That would make a difference of about 1mm per spoke.

I have already ordered washers. :+1:

The planning, particularly the identification of the correct spoke length, is indeed the most intimidating part. That’s why your help is really, really appreciated. All in all I‘m positive that things are working out rather well. Really looking forward to leaving the theoretical part and finally get to the actual lacing, though.

1 Like
2533

I just realized - a tiny ambiguity about spoke length - I am pretty sure that the measurement for ERD, and by those who sell spokes, is from the inside of the J bend, but the equation already adjusts for this (i.e. r3 which is half the spoke diameter, about 1.1mm, is subtracted). btw, the Squorx nipples seem an interesting design.

2534

Squorx are interesting indeed. Not essential in any way, but they have some advantages. There’s the Torx end to avoid damaging the nipples when tensioning and trueing the wheel (a slit works too, but is more prone to slipping and damaging, especially with aluminium nipples) and there’s the hemispheric shape of the area that contacts the rim. That is also available in a more ordinary nipple with the slit at the back. So, yeah, they’re interesting but not essential.
I even started fancying a snowflake spoke pattern, but came to the conclusion that a wheel with the Schlumpf hub is not the right project for such an endeavour. Maybe I will get back to the idea with a future wheel build.

1 Like
2535

Anyone here have had experience with one of the new freewheel Schlumpf hubs? That’s a lot of money, and I wonder whether they are worth every cent. Especially, how fast do they engage? Do you feel they are solid enough for riding muni?

I’m imagining a G36er with freewheel on both gears. That’d be amazing :heart_eyes:

1 Like
2536

I’m not sure if it’s legal, but you should ask Florian Schlump how many and to whom he sold theses hubs.

It makes me think that CDK sold 5 QU-AX Pipifax hub in 1 and a half years… even though it’s the best freewheel hub in the world :star_struck:

2 Likes
2537

I think historically freewheel Schlumpf hubs were mostly sold to Bicymple and a few other weird “novelty” bike companies, with freewheel in both gears.

I would be fascinated to know whether anyone bought the latest generation with freewheel on one of the gears.

2 Likes
2538

Ok, I just read an e-mail that Florian sent me today. My hub should be delivered next week. And the best part: the hub is cheaper than expected, thanks to a winter sale starting this month :partying_face:
Extras for 32h and brake disc are free of charge, and the price hub itself is reduced by 20%! Non-disc hubs are even 30% cheaper!
I thought I let you guys who were hesitating because of the price know. It’s still a lot of money, but it’s also a lot less than I expected.

https://www.florianschlumpf.swiss/index.php/en/unicycle-hub-order-form

Really looking forward to build the wheel and dive into a new unicycling experience.

Not directly related to Schlumpf hubs, but while I’m sharing information on unicycle deals: unicycle.com UK has the Nimbus Oracle 36" on sale. Don’t ask me how I know… :blush: :partying_face: :uni:

https://www.unicycle.co.uk/36-nimbus-oracle-unicycle-green.html

4 Likes
2539

I may reconsider my opinion on freewheel Schlumpf hubs… :laughing:

3 Likes
2540

Some more info from Florian on his freewheel hubs, and the possibility to move to a Qaxle interface:

  1. Freewheel: it’s a modified clutch, that allows to integrate it either on the low or high-gear side (or both, if you like).
  2. It has 12 positions of engaging.
  3. Why our sales promotion now? When we started the last production run, we were faced with an extreme increase in costs. Added to this were poor exchange rates for most of our customers, or in short: the hub became a luxury product that only a few riders could afford.
    I want to revitalize the business, of course, and give riders a chance to buy a hub who simply couldn’t afford it recently.
    Whether we will ever make a hub with this new interface is unclear. It would completely change the entire design, as the axle diameter is larger and therefore not a single part remains the same, from the ball bearings to all the gear parts and the outer diameter.
    The future will show how the market develops. At the moment, it seems to me to be rather restrained.
2 Likes
2541

That is bad news…

All the rest is good news (especially the part about the promotion)

2542

Well, not great news for the freewheel part. 12 points of engagement is shitty. This is 6 less than a cheap Nimbus Drift Trike hub. That means you can pedal 30° without actually moving the wheel forward. That’s insanely bad.

2543

I assume that the number of engagement points is more or less correlated with hub durability or is it just the number of pawls?
The fact that there’s play is one thing, but not being able to put torque on the climb is another, which seems just as important to me.
I’m not aware of the minimum number of pawls needed for peace of mind when climbing a pass, for example.