if a Moulton would...

General cycling advice ( NOT technical ! )
Nessie23
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Re: if a Moulton would...

Post by Nessie23 »

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Jdsk wrote: 10 Apr 2021, 3:01pm
Has anyone produced an explanation?

(The larger moment of inertia (as above) would result in the opposite effect.)

Jonathan
I believe the inertia explains it. The larger wheel with greater inertia will require a greater force to get it moving and keep it moving on a level surface. However the test that Mick refers to is rolling down a hill so maintaining momentum is the dominant factor (assuming Mick and his mate are similar mass and their combined shape in their respective bogeys are also similar, to even out drag) then the greater inertia of the larger wheel wins the day. Colin’s observation of a larger diameter wheel smoothing out surface imperfections is also valid.
Jdsk
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Re: if a Moulton would...

Post by Jdsk »

The cylinders down the slope might bear some relationship to downhill carts, but they're very different from a bike on the flat. The propulsive force is proportional to mass for the former but independent for the latter.

But the answer for those cylinders is ... the acceleration down the slope is independent of mass and radius, but does depend on the distribution of mass along the radius away from the centre. That independence is often said to be counterintuitive. You can test the dependence on distribution with with a can of beans full and empty. (Other canned products are available.)

Jonathan
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Mick F
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Re: if a Moulton would...

Post by Mick F »

Try a big and empty can of beans vs an empty small can of beans.
Try a tiny light quarter inch cylinder against a same weight 2ft cylinder.

Try it, and report back.
Mick F. Cornwall
Jdsk
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Re: if a Moulton would...

Post by Jdsk »

I've already posted how that works for cylinders on slopes.

When you wrote:
Mick F wrote: 10 Apr 2021, 10:25amSo, as far as I'm aware - all else being equal - that bigger wheels roll better than smaller wheels.
were you referring to cylinders on slopes, or to bike wheels on the flat? The effect of diameter is different.

Thanks

Jonathan
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simonineaston
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Re: if a Moulton would...

Post by simonineaston »

As one who's ridden Moultons of sundry stripe for years, I would venture to suggest that using one wouldn't necessarily guarantee the relief sought by the OP... I think as a general rule, the OP's symptoms could just as well be ameliorated by careful & considered changes in setup on a DF machine. Such care would be required when setting up the Moulton anyway - using one wouldn't automatically bring about a transformation in comfort. There's one caveat, which has been referred to already, indirectly, which is the higher up the Moulton status tree you go, the smoother the front suspension. The TSR is a sweetspot for many, for price versus performance, and Iandesud has praised his more expensive Jubilee - I can vouch for the effectiveness of the New Series front suspension, but few people want to visit that rarified atmosphere... Personally, I'd be tempted to work on your existing bike, your posture on it, your choice of 'bars and their covering first, while maybe seeking out a cooperative Moulton owner (I see one such has volunteered already!) with a view to a short/medium term loan.
S
(on the look out for Armageddon, on board a Brompton nano & ever-changing Moultons)
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Mick F
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Re: if a Moulton would...

Post by Mick F »

Jdsk wrote: 10 Apr 2021, 6:26pm I've already posted how that works for cylinders on slopes.

When you wrote:
Mick F wrote: 10 Apr 2021, 10:25amSo, as far as I'm aware - all else being equal - that bigger wheels roll better than smaller wheels.
were you referring to cylinders on slopes, or to bike wheels on the flat? The effect of diameter is different.
I'm talking about a slope to get it going, and then level to measure the roll-out.

My test at the railway station has a gentle slope of a dozen yards, then level for a hundred yard(ish).

Satellite view.
Red blob is start.
Blue blob is where Moulton finishes
Green blob is where Mercian finishes.
Roll-Out.jpg
Mick F. Cornwall
Jdsk
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Re: if a Moulton would...

Post by Jdsk »

Mick F wrote: 11 Apr 2021, 9:29am
Jdsk wrote: 10 Apr 2021, 6:26pm I've already posted how that works for cylinders on slopes.

When you wrote:
Mick F wrote: 10 Apr 2021, 10:25amSo, as far as I'm aware - all else being equal - that bigger wheels roll better than smaller wheels.
were you referring to cylinders on slopes, or to bike wheels on the flat? The effect of diameter is different.
I'm talking about a slope to get it going, and then level to measure the roll-out.
There are two different phases there: the acceleration down the slope and the decelerating run along the flat section.

And multiple variables between bikes including inertia of wheels, rolling resistance, air resistance and mass. The inertia of the wheels would have a smaller effect than the rolling resistance and air resistance.

Jonathan

PS: Now that measurement of speed is so easy and cheap it's possible to use run-out tests from a matched speed on the flat which removes the complexity of having two phases.
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Mick F
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Re: if a Moulton would...

Post by Mick F »

............. but that's what it's all about isn't it?
Riding a bike isn't a constant speed thing. You stop and start and you go down hills.

Two bikes going along the flat side by side, and the riders stop pedalling simultaneously will produce the same results as my car-park roll-out tests.

My experiments are allowing the bikes to roll down a gentle slope for a few yards, then rolling along on the flat to see how far they roll.
Results are always repeatable and consistent.

Done it with a few different bikes ................. and even an old MTB altering the tyre pressures and strapping a concrete block to the frame to add weight. Not much different in those trials. Tyre pressure (within reason) didn't make much difference, and neither did the concrete block.
Mick F. Cornwall
Jdsk
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Re: if a Moulton would...

Post by Jdsk »

Mick F wrote: 11 Apr 2021, 1:38pmTwo bikes going along the flat side by side, and the riders stop pedalling simultaneously will produce the same results as my car-park roll-out tests.

My experiments are allowing the bikes to roll down a gentle slope for a few yards, then rolling along on the flat to see how far they roll.
Those are different experiments. They will produce different results if the speeds at the bottom of the slope are different. But if they're only running down hill for "a few yards" that effect will be small.

How fast are they typically going at the bottom of the slope?

Jonathan
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Mick F
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Re: if a Moulton would...

Post by Mick F »

Here's me with Moulton in January this year.
Came up the hill out of the village, and then round and round a couple of times at the station before carrying on with the ride.
Just checked the data, and it was 5.2mph.
Screen Shot 2021-04-11 at 14.05.57.png
Mick F. Cornwall
rogerzilla
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Re: if a Moulton would...

Post by rogerzilla »

Mick F wrote: 11 Apr 2021, 9:29am
Jdsk wrote: 10 Apr 2021, 6:26pm I've already posted how that works for cylinders on slopes.

When you wrote:
Mick F wrote: 10 Apr 2021, 10:25amSo, as far as I'm aware - all else being equal - that bigger wheels roll better than smaller wheels.
were you referring to cylinders on slopes, or to bike wheels on the flat? The effect of diameter is different.
I'm talking about a slope to get it going, and then level to measure the roll-out.

My test at the railway station has a gentle slope of a dozen yards, then level for a hundred yard(ish).

Satellite view.
Red blob is start.
Blue blob is where Moulton finishes
Green blob is where Mercian finishes.
Roll-Out.jpg
I did a rollout test with a Brompton (349 x 32 Kojak) and a tourer (700 x 30 Marathon Racer) a few years ago. The Brompton did not do well at all. It was on very fine-grained tarmac and the difference would be even starker on a rough bit of road.
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Mick F
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Re: if a Moulton would...

Post by Mick F »

Well, there you go.
Bigger wheels roll better than smaller wheels.

Maybe shopping trollies should have 1ft diameter wheels instead of a silly little ones. :wink:
Mick F. Cornwall
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gazza_d
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Re: if a Moulton would...

Post by gazza_d »

This has veered off into interesting areas.
Firstly I agree with those who who say that a Moulton could help, but it may not. You would need to set the front suspension to be quite soft, but it could reduce the road buzz a bit. Try and find a dealer with one you could use for a test ride perhaps, or if adventurous buy one second hand to try. They hold their value so if it doesn't suit you could probably quickly sell it on again.

Secondly, the discussions around whether Moultons are more or less efficient than big wheelers.
In last spring's lockdown I started cycling a 12.5 mile lockdown loop with 300 ft of ascent, which is a mix of roads and surfaces. I did it a few times on the APB which is equipped with a dynamo hub and an alfine 11. I also did a couple of rides on my oldish steel Carrera Virtuoso with 14 speed Shimano. The Carrera is stripped down as far as poss with no lights, guards or racks etc, unlike the APB which is "fully loaded". The Carrera has 25mm gatorskins, whilst the APB has the 28mm Nutrak tyres.

When out for an hour so so I tend not to spare the horses.
I was surprised that the Carrera was actually slower by a handful of seconds. I have another comparison which is just a mile around the roads where I live and again the APB is quicker than the Carrera. It's not really long enough to be a useful comparison unlike the 12 miler though.

I suspect a lot of that is that the Moulton has better roadholding and handling and is quicker on the unpaved sections (2) which offsets any drag inherent from the hub gear and dynamo. I was definitely more fatigued on the Carrera as well and it was a good reminder of how plush the Moulton ride is and that is worth more to me than a few seconds an hour.
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531colin
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Re: if a Moulton would...

Post by 531colin »

Which bike fits?
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Mick F
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Re: if a Moulton would...

Post by Mick F »

531colin wrote: 12 Apr 2021, 8:31am Which bike fits?
For my own answer to this question, I spent some time getting Moulton to the exact setup as Mercian. Saddle height, setback, bar height and reach, bar shape and design too. They even share the same saddles and pedals.

Other than the feel and performance of the bikes, they are identical in every respect ............. and that's what I wanted.
Mick F. Cornwall
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