Any reason NOT to use a Shimano Nexus & Schlumpf Mountain Drive on a Street Machine?

The Shimano Nexus 7/8 hubs aren't available as options on the HPVelotechnik website... is there a reason for this apart from trying to get you the, by all means better, Rohloff Speedhub?

Like the title says, I'm interested in combining the Nexus hub with a Mountain Drive. The combination seems like a comfortable way to have a wide range of non-repeating gears without having to deal with derailleurs (as far as I can tell, but I'm a newb) and without spending an arm and a leg.

Any obvious reasons not to do this that I'm not aware of?

(I posted this on the BROL forums and haven't gotten a response... sorry about the duplication if that offends anyone)

 

I was hoping to see more replies to your question since this appears to be the way to escape all deraileurs.

Can you recommend another site/thread where this topic is discussed in more detail?

 

You could post the question on the Bentrideronline forums, in the either builders section or the main discussion area. Another possibility is to email someone at Shimano and Schlumpf. There may be a limitation for one or both which would preclude you from using them together, or perhaps it's not done because of the combined inefficiencies.

 

Schlumpf - SRAM S-7 has been done. There is even instructions on one of their sites on combining the two epicyclic drives. One folding bike manufacturer has a S-7 with high speed drive. I've heard of folks using the combo on recumbant trikes. I remember one person combining a Schlumpf with a Nexus 7 on a Trailmate Funcycle.

The down side is you are loosing additional efficiency with the cascading of those drives. Either of the Schlumpf or Nexus is well below the Rohloff in efficiency before you multiply their efficiencies together. There is also a weight penalty associated with either over derailleus, and two systems will be mildly heavier than the Rohloff. As for non-repeating gears, you'll still get some, but fewer with the mountain drive than the speed drive or high speed drive.

The particular manufacturer you cite is European, so SRAM would be more likely if they were to combine epicyclic systems than Nexus. FWIW, the Nexus 4 has broader range than the small step increase Nexus 7, and would be less expensive and lighter if you do choose to combine two internal drive systems. Also, the SRAM S7 has broader dynamic range than the Nexus 7. I own an HPE Corsa tadpole from the 80s that has a Sturmey 5 and a Sturmey 3, and the efficiency losses are high.

 

Schlumpf - SRAM S-7 has been done. There is even instructions on one of their sites on combining the two epicyclic drives. One folding bike manufacturer has a S-7 with high speed drive. I've heard of folks using the combo on recumbant trikes. I remember one person combining a Schlumpf with a Nexus 7 on a Trailmate Funcycle.

The down side is you are loosing additional efficiency with the cascading of those drives. Either of the Schlumpf or Nexus is well below the Rohloff in efficiency before you multiply their efficiencies together. There is also a weight penalty associated with either over derailleus, and two systems will be mildly heavier than the Rohloff. As for non-repeating gears, you'll still get some, but fewer with the mountain drive than the speed drive or high speed drive.

The particular manufacturer you cite is European, so SRAM would be more likely if they were to combine epicyclic systems than Nexus. FWIW, the Nexus 4 has broader range than the small step increase Nexus 7, and would be less expensive and lighter if you do choose to combine two internal drive systems. Also, the SRAM S7 has broader dynamic range than the Nexus 7. I own an HPE Corsa tadpole from the 80s that has a Sturmey 5 and a Sturmey 3, and the efficiency losses are high.

 

I don't belive the increaded drag is as much a factor as some people make it out to be. Schlumpf tells on there web site what is compatable and I belive the setup you are talking about will work. If you go to www.kinetics-online.co.uk you can find there gear calculator that loads onto your computer. This calculator is fun it gives combos for schlumpf to external or internal geared systems and says them by name.

 

The Harris Cyclery/Sheldon Brown web site has a lot of information on internal hubs. You might want to check out Sheldon's discussion of fitting a Nexus hub into an existing bike: http://sheldonbrown.com/nexus-mech.html

It looks like their might be issues regarding the dropouts. Even if you can get around the problem of not having horizontal dropouts (which allows you to set the chain tension), the hubs use a special washer which maintains the orientation of the axle (and with it the shifter).

 

This thread has been around a while. Has anyone done this yet?

Vertical dropouts on a trike would not seem to be a problem if the front boom is used to adjust chain tension.

Does anyone know of any site that has good technical pictures of the Nexus hubs? The Shimano corporate site is worthless for any documentation or technical information.

 

I was considering doing a similar conversion to my bike. I've been commuting on a Bianchi Milano with a Nexus 8 hub. It is wonderful! I really like the features of the hub. The friction losses are one of those initial concerns that go away with use. They are minor in the grand scheme of things. Also, the gears wear together (5-600 miles) and make the "friction sounds" go away for the most part. I have decided against doing it for one reason.

Getting a rear flat tire is truly a PITA! To swap tubes, you need tools, the instruction manual, and time. It is easier to leave the tire mounted, pull the tube, and patch. After stuffing the patched tube back in, pray you will make it home without another flat.

If you decide to go this route, buy many CO2 cartridges and keep filling the flat tire right to the bike shop. Some bike shops will not know how to remove and remount the Nexus. They may pass on helping you or charge you shop rate to learn on your bike.

 

The ant-rotation washer has prongs that fit into the droppouts. Should substitute fine. As for droppout orientation, could be an issue though.

 

The driving of those gears result in a 1% efficiency loss in the direct drive (the turning gears are unloaded) of the Schlumpf and 5% extra loss in reduction/overdrive ratio (the turning gears are loaded). You will see slightly larger losses with the Nexus. Compounding two losses of over 5% is a pretty hefty penalty. There will be some applications where a broad ratio without ders may be worth it such as folding bikes and/or belt drive systems, but it needs to be factored in when electing to go that route.

 

I have tried using the Schlumpf speeddrive with a Rohloff. In the direct gears there was no extra friction/drag noticeable. In overdrive and gear 7 there was so much friction it was like pedalling through toffee.

The drag is multiplied, not only added to.

Any gear setup using two hub gear systems will have gears where everything inside is working away fully, and creating drag. Take those gears and multiply the gear by using another hubgear - and multiply the drag also.

Its ok to do, but understand that there will be some extra extra drag in certain gears.