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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 11:16:10 -0600
Organization: Yellow Jersey, Ltd.
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On 3/2/2025 10:10 AM, AMuzi wrote:
> 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
> 

edit: 'not a much lower low gear'

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