Monday, 11 April 2011

Sachs 5 speed Torpedo Pentasport hub gear


This is a Sachs 5 speed Torpedo Pentasport hub gear - which is quite a mouthful of a name for a nice little german hub gear. This is the hub that will be going into my Stowaway build. It isn't stamped with a year and month as Sturmey Archer's handily are, so I can only guess at it's age. It is marked Sachs so precedes their taking over by Sram in 1997 and the 5 speed was introduced in 1987, so it's from sometime within that period.

It has got pretty respectable range of 251% which puts it a fair bit wider than a standard 3 speed (177%) and not too far away from my Shimano Nexus 8 (306%). The size of the steps between gears is also nice and even, with slightly shorter steps at either end of the range (1-2 & 4-5).

These Sachs/Sram hubs don't use a pull-chain that shorter range 3 speeds use, instead it has a 'clickbox' which clamps over the top of two push rods. The push rods are sleeved one inside of the other and when pushed in certain combinations will activate all 5 gears in sequence. It's this certain sequence that is dealt with inside the clickbox. The big advantage of this is that there is no adjustment to do, you just screw on the clickbox and hey-presto all 5 gears are selectable. The possible disadvantage of this is that the shifter, cable and clickbox come as a one piece unit. They are seperable, but each part is very specific and you can't for example just replace the cable as the cable is a solid wire with a special end fitting. You see most bike cables just have to pull, this cable has to push & pull. - which is a different kettle of fish. Basically if you need a new one, just go on ebay.de and buy the whole thing for a few euros.

Another aspect to this hub is the metal cover plate on the drive side of the hub. It's quite large. Meaning that the hub can't accept very small sprockets such as 15/14/13 maybe also 16. I haven't tested further, but it should be ok with sprockets larger than this. You can see in the wheelbuilding photos below that I've put a 15 tooth on just to hold the plate on whilst I do the build and this doesnt have enough clearance. This would probably make the hub unsuitable for smaller wheels such as a Brompton as they need small rear sprockets to maintain.a sensible gear range. But on this bike with 451mm wheels a 46 tooth front ring and, for example, an 18 tooth rear would give gear inches of 32 to 81 - a nice range.

I did open up the clickbox on mine out of simple curiousity and it was a bit of a mixed bag, it was a good thing because I renewed the grease inside of it, but a bad thing because it is quite fiddly to put back together.


Above is a view of the inside of the clickbox with some new grease in there. There isn't anything to worry about with this though, the casing and components are very solid and it is very well sealed. I only opened mine to regrease it because this thing is a minimum of 14 years old.

I've had this hub for a while, having got it off ebay in the spur of the moment sometime last year. So when I started thinking about what to put in my Stowaway built this seemed the obvious choice. Before I started building it into a new 451mm wheel I opened it up for the first time just to check if it needed regreasing.


It's a very simple hub to open. Much simpler than for example the well known Sturmey AW 3 speed. All you have to do it undo the two nuts on the none drive side (shown above),....
....then slide off the two retaining washer thingies.....

...and take off the big plastic dust cap. Once you have done that then the entire hub shell just lifts away from the internals - see below.


At first glance the inside of the hub doesn't look too delightful. but looking closer its actually very well greased up and doesnt require any attention. It has been regreased at somepoint by a previous owner using somekind of grey moly grease. Whatever it is, it is working just fine, so for the time being I'll leave it as it is. Below is the internals side by side with the shell.

With that done it's time to build it into the rim.
First of all the wheel needed a slight dish and fingers crossed this will all line up ok when the bike is built. Secondly the Damon Rinard spoke calculator Excel spreadsheet on Sheldon Brown's site came up with needing spokelengths of 198.5mm and 201.1mm for a 2 cross pattern. However I knew from building the Hopper that the calculator seems to overvalue the lengths by around 6mm. Maybe I'm using it wrong (I'm pretty sure I'm not), but I ordered lengths of 192mm and 194mm from SJSCycles and low and behold they were the perfect size. The rim is a Sun Ringle ICI-1 from Chainreactioncycles. They are very nice rims and the cheapest 451mm that it seems you can get with 36 spokeholes.


Starting off by loosely fitting a spoke from every other flange hole to every 4th hole along rim hole.

Then doing the same on the otherside
Now you start crossing the spokes by filling in the gaps on the hub flange with spokes coming in from the opposite side, crossing over the top of the next spoke and crossing under the spoke beyond that. That probably makes no sense, but there are much better wheelbuilding tutorials on the web than I can offer, besides the best way to understand it is to just build one and find out.
And repeat on the opposite side. Easy really. This is the first time I've built a wheel using brand new rims and I can tell you it is infinitely easier than using secondhand rims or existing ones from your bike. It simply laced up and was running tight and true without the slightest bother. (The Hopper wheels - built from well used BMX rims where the complete opposite and a real pain in comparison)




4 comments:

  1. Nice rim... Sachs are the best at hub gears.... Much better than Shitmano.

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  2. Thanks for this post... it's the only one I've found that takes apart the shifter.

    I have an (older?) Sachs Torpedo 5 speed pentasport shifter... it's a two cable hub gear... the gears work but the thumb shifter is broken... and I'd like to fix / replace it.

    Pictures here and here:

    http://www.flickr.com/photos/ciaranryan/6267275773/in/photostream/

    http://www.flickr.com/photos/ciaranryan/6267275547/in/photostream

    My bike only has the thumb shifter and not the additional click box that yours has, at the end of the cable.

    So, my question is: German ebay sells your version of the thumb shifter... if I bought one do you think my two gear cables would fit into it and allow me to change gears?

    Thank you for any advice you can give... info is hard to find.

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  3. I'd doubt that a shifter like mine would work on yours. My shifter works because the clickbox is pushing the two pushrods in a predetermined pattern. Your two cables will be doing the same kind of thing but Id guess in the same way an old Sturmey 2x cable 5 spd did which is a cable going into each side of the hub - totally different design really.

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  4. I just stumbled upon this hub and restored it, but i was trying to find some info about it and found this interesting link (http://www.all-about-hubs.com/start.php?action=naben_galerie1_en). It says there that it's dated from 1992 to 1998, just thought you might like that.

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