Moulton SST -- reasons (not) to buy?

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Brucey
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Re: Moulton SST -- reasons (not) to buy?

Postby Brucey » 9 Mar 2019, 11:21am

reohn2 wrote:
Brucey wrote:all the evidence is that the moulton fairing is very far from 'no advantage at all' and that adverse windage on it is not likely to be a major problem.

cheers

Show me the evidence


as suggested here

https://www.bikeradar.com/road/gear/article/bicycle-fairing-50204/

you should read 'bicycling science' by Whitt and Wilson. Fairings are not banned in racing by the UCI purely on safety grounds....


As I have noted already practical experience of the adverse windage of a fairly large object that is frame mounted at the front does not seem very severe. The side windage of the moulton's Zzipper fairing is a small fraction of the windage of the rider.

cheers
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hercule
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Joined: 5 Feb 2011, 5:18pm

Re: Moulton SST -- reasons (not) to buy?

Postby hercule » 9 Mar 2019, 11:49am

Brucey wrote:
Mick F wrote:PS
As for drag of a SA hub, one comparison I can make, is comparing front vs rear.
Front has a hub dynamo.

Rear spins far better, meaning that the hub dynamo produces more drag than the SA hub.


A good portion of the drag in an IGH is in the gear transmission; this doesn't turn during freewheeling, so doesn't add drag. Try turning the rear wheel backwards and see how you get on.

cheers


Is the drag in reverse of much relevance then? I have the SA fitted to my recumbent trike for a wider gear range, thinking that it might be bearable in terms of drag, but in practice it’s been unnoticeable at least by me. I have another couple of machines with Sachs 3x7 hubs, and they are definitely draggy in all but direct drive.

The nature of trikes is that sometimes you do need the go backwards, a little resistance to motion is no bad thing in those circumstances!

reohn2
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Re: Moulton SST -- reasons (not) to buy?

Postby reohn2 » 9 Mar 2019, 1:33pm

Brucey wrote:
reohn2 wrote:
Brucey wrote:all the evidence is that the moulton fairing is very far from 'no advantage at all' and that adverse windage on it is not likely to be a major problem.

cheers

Show me the evidence


as suggested here

https://www.bikeradar.com/road/gear/article/bicycle-fairing-50204/

you should read 'bicycling science' by Whitt and Wilson. Fairings are not banned in racing by the UCI purely on safety grounds....

I'm not interested in racing

As I have noted already practical experience of the adverse windage of a fairly large object that is frame mounted at the front does not seem very severe. The side windage of the moulton's Zzipper fairing is a small fraction of the windage of the rider.

cheers

Whilst I agree about the windage of rider and fairing,the fairingonly adds to riders windage,and my concerns are in adverse and changing windage,changing direction on a windy day,blustery winds,riding past gate opening,HGV's overtaking at speed,etc,etc.
In other words normal UK road riding conditions,as I stated before the fairing in question can be like a sail.
I'm going to leave it at that.
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Brucey
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Re: Moulton SST -- reasons (not) to buy?

Postby Brucey » 9 Mar 2019, 4:22pm

unless you have ridden with something like that you can't say if or how bad it really is. IME having something large that turns with the steering can be b.awful but something that doesn't turn is nothing like so bad.

You may not be interested in racing but I have yet to meet a cyclist that isn't at least mildly interested in going faster for less effort and that is what a fairing can do for you.

More reading here

https://www.notechmagazine.com/2013/04/ride-your-bike-faster-or-with-less-effort-using-a-partial-fairing.html

Image

in which they look at a handlebar mounted (i.e. turning) fairing and yes they do note that it is adversely affected by crosswinds, but they don't say it is a show-stopper. The same size fairing mounted on the frame instead is going to be considerably more benign; it adds only a small fraction to the total side windage of the machine.

cheers
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pete75
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Re: Moulton SST -- reasons (not) to buy?

Postby pete75 » 9 Mar 2019, 4:32pm

Brucey wrote:the notion that motorcycles are somehow not terribly vulnerable to side winds is one that is quickly dispelled by riding one in adverse conditions. They vary considerably too.


cheers


Oh yes and it depends where the windage is as well. When Honda tried to do alloy wheels on the cheap with their Comstar wheels - a cast alloy rim with broad pressed steel "spokes" they were really dreadful in cross winds presumably due the wind's effect on the front wheel. For a few winter weeks back in the mid eighties I used a s equipped CB400 twin for journey to work. Twelve miles each way in the fens. Not the best place for a machine that's unstable in anything from a fresh breeze upwards.

reohn2
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Joined: 26 Jun 2009, 8:21pm

Re: Moulton SST -- reasons (not) to buy?

Postby reohn2 » 9 Mar 2019, 4:47pm

Brucey wrote:unless you have ridden with something like that you can't say if or how bad it really is. IME having something large that turns with the steering can be b.awful but something that doesn't turn is nothing like so bad.

You may not be interested in racing but I have yet to meet a cyclist that isn't at least mildly interested in going faster for less effort and that is what a fairing can do for you.

I meant I not interested in racing in this context.

More reading here

https://www.notechmagazine.com/2013/04/ride-your-bike-faster-or-with-less-effort-using-a-partial-fairing.html

Image

in which they look at a handlebar mounted (i.e. turning) fairing and yes they do note that it is adversely affected by crosswinds, but they don't say it is a show-stopper. The same size fairing mounted on the frame instead is going to be considerably more benign; it adds only a small fraction to the total side windage of the machine.

cheers

I take your point about steering mounted v frame mounted,but my point is that wind can come from any and all directions in one ride especially in a traffic heavy UK and where the winds can be strong and blustery.It's not an exact science our weather conditions
We'll agree to differ shall we?

PS, in any case that beard would negate any advantage the fairing offered :wink:
Last edited by reohn2 on 9 Mar 2019, 4:54pm, edited 1 time in total.
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Brucey
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Re: Moulton SST -- reasons (not) to buy?

Postby Brucey » 9 Mar 2019, 4:54pm

Image

1/12th scale model won't catch the breeze so badly.....

IIRC the CB400N and the sister 250 model had 'nice light steering' so novice riders wouldn't feel like they had to muscle the (fairly heavy) machine in and out of turns. If so, this may have been achieved by having more fork offset, which would have increased the (turning) windage on the front wheel assembly. More fork offset has a fairly brutal effect on the turning windage; you don't need much offset before about 2/3rds of the side area of the wheel is ahead of the steering axis and acting like a backwards rudder.

Re fairing windage; you only need concern yourself with side winds, or at least the side wind component; tail winds allow the body to shelter the fairing and headwinds exert less force than normal (which is the whole point of the thing). R2, I kind of got the point that you are not going to rush out and buy a fairing but that is not to say that your reasons for so doing (or not) are well founded (or not). Boring old science and practical experience suggests that the upsides may outweigh the downsides if you go about it in the right way.

cheers
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Brucey
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Re: Moulton SST -- reasons (not) to buy?

Postby Brucey » 9 Mar 2019, 5:29pm

Image

cheers
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reohn2
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Re: Moulton SST -- reasons (not) to buy?

Postby reohn2 » 9 Mar 2019, 5:33pm

Yeah right! :)
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pete75
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Re: Moulton SST -- reasons (not) to buy?

Postby pete75 » 9 Mar 2019, 5:53pm

Brucey wrote:Image

1/12th scale model won't catch the breeze so badly.....

IIRC the CB400N and the sister 250 model had 'nice light steering' so novice riders wouldn't feel like they had to muscle the (fairly heavy) machine in and out of turns. If so, this may have been achieved by having more fork offset, which would have increased the (turning) windage on the front wheel assembly. More fork offset has a fairly brutal effect on the turning windage; you don't need much offset before about 2/3rds of the side area of the wheel is ahead of the steering axis and acting like a backwards rudder.


cheers

The 400 was for people who'd passed their test so not really a novice. Back then I think they may have been bought by more experienced, mature riders as younger guys usually got a 650 or 750 after test passed.
I'm pretty sure it was the wheels. A girlfriend had the previous model CB250 with wire wheels and that was ok in cross winds.

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deliquium
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Re: Moulton SST -- reasons (not) to buy?

Postby deliquium » 9 Mar 2019, 6:16pm

Perhaps AI could be employed to prevent thread drift (the collective scourge of fora) - or any other means, please?

:wink:

It's a man thing isn't it?
Current pedalable joys

"you would be surprised at the number of people in these parts who nearly are half people and half bicycles"

brumster
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Re: Moulton SST -- reasons (not) to buy?

Postby brumster » 9 Mar 2019, 8:47pm

Brucey wrote:Image

cheers


I'll have to time myself next time I'm wearing my cape on the rainy commute !

Brucey
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Re: Moulton SST -- reasons (not) to buy?

Postby Brucey » 10 Mar 2019, 6:48am

pete75 wrote:I'm pretty sure it was the wheels. A girlfriend had the previous model CB250 with wire wheels and that was ok in cross winds.


if the mudguards were similar and the steering geometry was the same then it might well have been. But a relatively small change in fork offset can make a much larger difference in the turning windage than you would ever be likely to get from the difference in spokes.(*) (unless they were somehow acting like wings in a crosswind....?)

IIRC (and I'm really dredging the old memory banks here) the steering geometry of the 400N model was almost identical to the 250N. Both the 400N and the 250N models were much heavier bikes than the predecessor models and they may well have made the steering lighter (more fork offset = less trail) than the predecessor models for the reasons I previously noted. [I had a '87 CB350S and that was no good in crosswinds either despite unexceptional four-spoke wheels. It had very similar steering, weight etc as a CB400N...]

(*) for example if you have a wheel of 24" rolling diameter, then a 3" fork offset is enough to put ~2/3rds of the wheel area ahead of the steering axis. This will make for a lot of turning windage regardless of the spokes used.


The above is relevant to the discussion about side wind stability; for example it is obvious that a bar bag is going to be a bit like the rudder on a boat sailing backwards but folk automatically suppose that if their low-rider panniers are more or less centred on the front wheel they can't contribute much to side windage; nothing could be further from the truth. Panniers ought to be set so that they are centred on the steering axis to avoid turning windage effects, i.e. they should be set backwards/downwards by the same amount as (or a little more than) the fork offset.

cheers
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pete75
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Re: Moulton SST -- reasons (not) to buy?

Postby pete75 » 10 Mar 2019, 9:59am

deliquium wrote:Perhaps AI could be employed to prevent thread drift (the collective scourge of fora) - or any other means, please?

:wink:

It's a man thing isn't it?


Al who?? :lol:

hercule
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Joined: 5 Feb 2011, 5:18pm

Re: Moulton SST -- reasons (not) to buy?

Postby hercule » 10 Mar 2019, 10:32am

Moderator request: Can we have a Janet instead of an Al, please?

Janet.jpg


https://en.wikipedia.org/wiki/The_Good_Place

:D :D :D