PDR

I’m very pleased with my Brompton (2-speed titanium) but I would like a couple of extra gears for riding up the odd steep hill and riding down even faster. I currently have 56 & 74 gear inches, but I don’t want to add too much extra weight and I don’t want a second gear lever cluttering up the handlebars.

I spoke to Ben Cooper (Kinetics) last Friday and it looks as though a Schlumpf High Speed Drive will give me exactly what I want... a low 30” the standard 56”/74” and a higher 90” top gear. Plus it only adds 300g to the weight of the bike, a lot less than any other Brompton gear option.

I called into the LBS where I bought the Brompton this afternoon and it turns out that one of the guys is an experienced frame builder so reckons he could fit a high speed drive for me. This would save me the worry of shipping my bike up to Ben. Just need to confirm with Ben if there are any snags I might have to consider.

Does anyone here use this system on a Brompton or other type of bike?

pibach

As far as I know the Schlumpf is a good 1500g. I.e., ~700g heavier than other crank systems. Its one of the heaviest options to get more gears in fact.
Although I like it for its principle, I spoke with owners that had a lot of problems with the old version, noisy, greasy, leaky, etc. The newer model might be improved though, still just too heavy, unfortunately.
56 GI is good enough for most hills, if you are fit. No need for more gears. Just my 2 cents.

PDR

Thanks for that info, I had been told about 300g, but at 1500g it is not worth doing.
I’m fit enough for the hill up to work. I’d like higher gear for going downhill but I can just coast rather than peddle.

BruceMetras

A Schlumpf Speed Drive is 912g ..

BruceMetras

These are some odd calculations.. the Speed Drive is a 1.65/1 overdrive 2spd hub.. the High Speed Drive is a 2.5/1 overdrive hub.. if you geared your bike for a low of 30", then your 'standard' would be a 30"/48" when in direct drive.. if you have a Speed Drive, when engaged in overdrive, you would have 49.5/79.2 .. if you have a High Speed Drive engaged in overdrive, you would have 75" and 120"..

Speed Drive ratios would basically overlap at 48" .. 30"/48"/49.5"/79" .. so basically a wide range 263% 3spd

High Speed Drive (no overlap) 30"/48"/75"/120" .. here you have a true 4spd with 400% range ..

jur

... and so the extra weight is given by subtracting the old BB plus crankset... make that 900g plus 340g for the Schlumpf crank arms minus 900g(?) for the old stuff, and a smaller chainring and shorter chain, gets you very very close to 300g extra.

PDR

That would be good

If that is only 300g more than the standard 2 speed set up then I might consider it. But if it is 300g on top of the already heavy BWR, then no, it would be too much of an increase in weight.

gringo_gus

this is very interesting, it points to my concern that the brompton S2LX is a great bike, but two gears aint enough and any more and you start to lose the lightness that gives it such an advantage... be interested to see how this plays out. I guess one could get a lower lower gear and stick with two if it was uphill that was the problem ?

This isn't meant to be a criticism, I rode one and think its a great bike, but a big spend too...

jur

That would be 300g on top of the existing setup and (I'm guessing) about 700g lighter than the BWR.

PDR

The 2-speed is a great bike, but I’d just like a lower gear for the steeper hills (especially when it is windy) and a higher top gear for going downhill. If I can increase the gear range without adding too much extra weight then I reckon I would end up with the perfect (for me) folding bike.

PDR

Thanks Jur,
The difference between the 2 speed and the BWR is 732g so you where very close. So the HSD would give me a bike that is lighter than even the 3 speed.

The guy in the LBS was telling me that he had been on a manufacturers test day and had been trying out the nano? electric Brompton conversion and he said it was very good might be something to look at in years to come when I’m old.

jur

I had a folder set up with a Schlumpf and a Duomatic... the 2 most often used gears in the middle required a double shift each time. The wide range 4sp PDR Brommie would be the same - a double shift between 50 and 75". But it would be easier to handle than the Duomatic/Schlumpf setup - the latter were both done by foot.

Before you take the plunge, do a more accurate weight calc, just in case we erred grossly somewhere in an assumed weight.

LWaB

The Nano-Brompton is no longer in production, the inventor has some medical problems. He is looking at getting somebody else to make it under license.

Juha

One thing to consider is, there'll be some internal friction with the Schlumpf. You'll have to decide for yourself whether you're willing to lose some drivetrain efficiency to get the extra gears. I don't know if anyone has attempted to quantify how much the loss in efficiency would be.

--J

invisiblehand

As Jur pointed out, in the two most likely gears, the Schlumpf would be engaged in one of them. However, solely from memory since I can't recall the source, I remember something like a 3% loss so it doesn't matter much.

PDR

I have decided to scrap the idea of the High Speed Drive due to the weight and several other issues.

I spoke to the Brompton Guru Steve Parry this afternoon and I’m now going for a much cheaper and easier mod that will leave the top gear @ 74” but drop the 54” gear a bit for better hill-climbing ability. After all it is hill climbing which takes effort, I can just coast down hills for free.

As Steve said, it is such a shame to add weight to the superlight Brompton, his mod does not add weight to the bike.

invisiblehand

Are you changing the cogs in the rear?

PDR

Yes, just the larger cog... having a custom one made

pibach

I am really wondering why you want a smaller gear. The steepest hill here (otherwise it is almost flat in and around Berlin) I can do in my 6th gear which is ~80 GI. Many singlespeeders are happy with only one gear in the high 70th. Also in hilly San Francisco. And there are people who tour the Alps with just one gear. Sometimes it is just a matter of technique. Good pedal grip and a strong handlepost is a basic prerequisite though. And not to wear business suit ;-)

PDR

“strong handle post”... are you suggesting that I should be standing up out of the saddle to peddle? It is something that I never do and I don’t like spinning furiously either. At 46 I'm still fit and strong but I'm just a little concerned as to what long term impact pushing high(er) gears up hills will have on my knees later in life.

I’m just thinking that I could do with a slightly lower gear for the long hills.

EvilV

Re weight:

A good dinner would add 800 grams to your outfit. If you like the idea go for it and hang the weight. I can never understand why people agonise over a few grams. Most of us are probably a good ten pounds over weight ourselves - some, a hell of a lot more than that. I could certainly lose a good 15 pounds to get back to the weight I was in my forties.

LWaB

Because they have to lift and carry a folding bike. It makes a difference.

Lewis Butler

Like this one from Highpath, PDR?



https://www.flickr.com/photos/plooifiets/2035772624/

LWaB

I think Highpath have stopped making the brazed double cog.

PDR

I think it is down to psychology. I bought the lightest possible configuration (bar the single speed) and I don’t what to end up saying “I’ve got a great gear range but the bike now weighs more than a steel 6-speed”. I do carry the bike a lot so every gram really does count.

I will end up with a 12/18 & 54T. It is a simple and inexpensive mod and I can also have a play with different size chainrings.