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From: AMuzi <am@yellowjersey.org>
Newsgroups: rec.bicycles.tech
Subject: Re: Getting old is not for sissies
Date: Sun, 2 Mar 2025 10:10:08 -0600
Organization: Yellow Jersey, Ltd.
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On 3/1/2025 8:06 PM, Frank Krygowski wrote:
> On 3/1/2025 4:39 PM, Jeff Liebermann wrote:
>> On Sat, 1 Mar 2025 13:55:50 -0500, Frank Krygowski
>> <frkrygow@sbcglobal.net> wrote:
>>
>>> IIRC, hydrostatic transmissions are standard features on 
>>> zero turn
>>> mowers. But as you noted, the mechanical efficiency is 
>>> lousy. That's not
>>> a concern if you have a big enough engine and low enough 
>>> use hours. It's
>>> a huge concern for a cyclist.
>>
>> True, but the huge concern is mostly for racing.  If 
>> you're using the
>> bicycle as a moving exercise machine, the added weight and 
>> increased
>> friction might even be considered beneficial.  It's like 
>> the weights
>> on barbells where light weight is not a concern.  For 
>> competitive
>> fixie racing, maybe the governing organization should 
>> specify a
>> minimum allowable bicycle weight, which might inspire 
>> technical
>> innovation instead of shaving grams off the bicycle weight.
> 
> I think that level of inefficiency would be a concern of 
> most cyclists, and very few actually race. It would take a 
> lot of fun out of riding.
> 
> I once worked on a bicycle belonging to a friend that had a 
> quite rare (at least, at the time) 5 speed Sturmey-Archer 
> geared hub. IIRC, there were two shift cables, one going to 
> each side. Anyway, as I remember when shifted to its lowest 
> gear it seemed extremely sluggish. Unlike the equivalent low 
> gear on a derailleur bike, it really didn't seem much easier 
> going uphill in that gear. Instead it just seemed slower. 
> And as I recall, that was a not uncommon complaint about 
> that particular hub.
> 
> I understand the desire for exercise. But I think almost 
> everyone prefers to get their exercise while moving farther 
> or faster, not by slogging along slowly. If that were 
> acceptable, we'd all be riding solid tires.
> 
> 

Odd symptom and no logical reason for it IMHO.

The S-5 gearbox (went through several variants) is basically 
an AW three speed design with dual sun gears. With no left 
side change, it's a three speed (+26.6% high, direct drive, 
-21.1% low).

When the left side is changed, the sun gear clutch slides 
over to the other gear set, giving -33.3% super low, direct 
drive and +50% high.

The gear sizes being different from an AW (-25% low, direct 
drive, +33% high), the five model notably gives a faster 
high gear but not a lower low gear.

Since everything is in the same oil bath* and rolling on the 
same bearing adjustment*, overall efficiency should vary 
only in the relative losses of gear diameter which is a 
small difference.


* can be correct or deficient

-- 
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971