The SRAM site does have info on the drum brakes in their online manuals, 1999 edition. I can't seem to reach it now, but www.google.com says the URL is at: http://www.sram.com/product/misc/tech_manuals/1999/99_techman_igh_english.pdf
If you search for "sachs vt-5000" on Google, you can get this URL as well as a text version of the document. The PDF version includes pictures.
For drum brake maintainence, it says:
M A I N T E N A N C E / C A R E O P E R A T I O N *
The hub mounting is sufficiently lubricated * The drum
brake can be controlled very and essentially maintenance-free.
precisely and provides very effective * Lubricate brake
cable regularly. braking deceleration compared with (Cable
housing without inner tube.) conventional bicycle brakes.
However, the * Do not clean hub with water under drum
brake only reaches maximum braking pressure (e.g. hard
jet of water, high- power after a certain breaking-in
period. pressure cleaner etc.) water penetrating * To
get used to the new brake, operate the could produce
corrosion in the brake brake lever carefully to acquire a
feel for 5b drum and cause malfunctioning. the drum
brake's deceleration. * Do not rinse hub with benzene,
petroleum 5a 5 etc. as this could produce impurities in
Advice: the brake pads The front brake is usually applied
using the * If the front wheel develops too much brake
lever on the right of the handlebars. lateral play, have
the mounting adjusted Some bicycle manufacturers may,
however, by a specialist.
From: David Rodenhiser - I remember that some time in the last couple of years, someone posted on this list a chart detailing the efficiency of the Sachs 3 speed internal hub at various power levels. I can't seem to find it in my archives. Does anyone have a copy they could forward to me?
Hi David, I guess this is what you are looking for:-
Measurements of Efficiency of Chain and Shaft Drives
Section 1.2.2 Contributed by Chris Juden, CTC Technical
Officer, email@example.com. The best work I know of on
this subject was commissioned by Fichtel & Sachs AG.
Comparisons of single-speed, multi-speed hub and
derailleur gearing were published in Radmarkt Nr.12/1983
and I am aware of other work within that company which
compared the efficiency of chains in various states of
neglect. Here's a summary of results, percentage
efficiency values estimated from the graphs printed in
New, clean, lubricated chain drives
1-spd 3-spd Hub Gear 6-spd Derailleur
Power Low 1:1 High 24T 19T 13T
50W 96.0 90.6 93.4 87.3 94.2 94.1 92.1
100W 97.3 92.8 95.7 90.9 96.2 96.4 94.9
200W 98.1 94.0 96.9 92.9 97.4 97.6 96.9
400W 99.0 95.0 97.9 93.9 98.1 98.4 97.8
Used chain (8000km), no rust, lubricated 100W 94-96%,
Neglected used chain (7000km), rusty, dry 100W 88%, 200W 93%
We can draw some interesting conclusions from these data. They confirm that hub gears are a little less efficient than derailleur, even in direct drive, and show that they work better in low than high ratio. With a derailleur: running the chain around the little pulleys takes only about 1W. And a misaligned chain is much less wasteful than small sizes of the sprocket, especially at low power levels. Indeed: at 50W the out of line 24T does a bit better than the in line 19T! 13T is not even very small by today's standards, but is clearly rather inefficient. At very high power levels however, alignment may become as important as size.
We have a tandem Greenspeed trike. Our Sachs three speed internal hub does not work in high gear. It cuts in and out. The local bike shops do not know much about them. It sounds like I might have to order a new hub for $225 plus installation. Does anyone know of a better solution?
Have you tried the techniques for adjusting the 3x7 written by Ian Sims? He's allowed me to post a copy on my Greenspeed resources web page: http://18.104.22.168/greenspeed/internal_hub.html When the hub is either out of alignment (i.e., it isn't centered in the dropouts, or the frame isn't straight), or when it's just not adjusted well, popping out of gear is a symptom.
The primary difference to me
between the 3X7 and a regular setup is the reduced drag
in the drivetrain. I don't want to start another thread
about this issue! This is only my personnal experience
that I am relating here and other people may have a
different opinion and a different experience. When I
first built up my Greenspeed GTR from a frameset in 1998
I decided to use a 3X7 hub (13,14,15,17,19,21,23 cluster)
and a Schlumpf type 1 (with 63 tooth chainring). This
gave me a very wide range of gearing with very small
increments between gears. Back in 1998 this worked out
great for me. I was 44 years old and in poor physical
condition. Ok, I was fat and way out of shape. The small
increments between gears allowed me to get just the right
gear under any circumstances. Last summer I replace the 3X7
with a 9-speed hub, 11-32 cluster, and SRAM 9.0 deraileur
just to see for myself if there was a difference. At that
point I had been commuting by trike 10 miles each way to
work for 3 months. I'm almost totally car-free now. Now
that I am 25 pounds lighter and probably in my best
physical condition since I left Army basic training in
1974, I find that I no longer need these small increments
in gearing. Maybe it's because I am much stronger and
much more used to spinning now. I don't really know why,
I just know that I don't find myself thinking it would be
nice to have a gear a little bit higher or a little bit
lower than the one I'm in. The trike feels more lively
and responsive without the 3X7. Maybe it's primarily a
weight issue, but I think I can also sense a bit of loss
going on in the 3X7, even in 2nd gear, that's not there
with the 9-speed setup. I don't remember how much it
cost, but it wasn't all that expensive. I think the
biggest cost was the deraileur and shifters. I was using
an old Dura-Ace deraileur with the tight cluster on the 3X7
so I had to replace it with a wider range deraileur. I
chose the SRAM 9.0 and it is absolutely terrific. The
longer grip shifts from SRAM also work better on the
trike than the old short ones.
On Wed, 1 Aug 2001 14:27:49 +0100, "Eric Jarvis" <firstname.lastname@example.org> wrote: ... But I see that a couple of manufacturers are selling trikes with Sachs 3x7 hubs which have been upgraded to 3x9. I have an upright with an existing 3x7 system and would like to know if it is possible to upgrade this to 3x9. If so what work and parts are required ?
This requires the use of a special lock ring (the part that holds the cassette on the freehub). This special lock ring is longer and allows you to fit the wider 9 speed cassette to the 7 speed hub body. This results in a wider hub, so you also need to add a spacer to the hub spindle. The modified hub is then 138mm wide at the dropouts, about 3mm wider than a standard 135mm mountain bike style hub. The trike frames are typically made with 138mm to 139mm rear dropouts, but you might be able to squeeze the modified hub into your existing upright's frame. There are a couple of other things to keep in mind. When you put a 9 speed cassette on a 7 speed hub the outermost one or two sprockets of the cassette will not engage the splines of the freehub body, and are only held in place by the extra long lock ring. At least for some folks, this can result in poor shifting between the outermost sprockets, since the shifting ramps on these sprockets are not being indexed into their proper positions by the splines. I have found it virtually impossible to keep the sprockets alined while tightening the lock ring. Most folks don't seem to have a problem with the shifting, so it may depend on the particular cassette, as to how critical it is to get the outermost sprockets alined properly. I heard from one person who epoxied the outermost sprockets together, and found that to be a fairly straight forward fix to the shifting problems. It also depends on whether your hub has a "compact" freehub body. If so, the splines don't actually go all the way to the end of the body, this is to allow the hub to take a 7 speed cassette with a 11 tooth outermost sprocket. I'm told, that if you use a hub with a normal "non-compact" body, and if you remove the dust shield from the body, that you can just barely get the outermost sprocket to engage the splines enough to keep it aligned while you tighten down the lock ring.
Thursday, 29 January 2009