Author Topic: Flints and tyres  (Read 1684 times)

LittleWheelsandBig

  • Whimsy Rider
Re: Flints and tyres
« Reply #25 on: January 06, 2019, 11:18:00 pm »
A velomobile doesn't wobble like a bicycle, so the rear wheel spends more time in the track of the front wheel, too.

The vast majority of velomobiles are trikes, so the rear wheel is rarely in the track of a front wheel.
Well yes, but we were talking about quads.

Quattrovelos have different track widths front and back.
http://en.velomobiel.nl/quattrovelo/maatschets.php
Wheel meet again, don't know where, don't know when...

LittleWheelsandBig

  • Whimsy Rider
Re: Flints and tyres
« Reply #26 on: January 06, 2019, 11:27:29 pm »
this was used on precast roadway sections, only in places where there was (seemingly) a skid risk.  Being precast the surface of the concrete is smooth.  I have never seen the coating (which is exactly as described earlier, and accordingly has no resemblance whatsoever to chipseal) used on anything else, thank goodness; in causing bicycle tyre punctures it would come a close second to just strewing drawing pins all over the place.

cheers

A smooth concrete surface has a good friction coefficient.
https://www.gomaco.com/Resources/worldstories/world36_1/bristol.html

I have no idea what type of surfacing you are talking about as usually the aggregates used in normal bituminous pavements (asphalt or whatever) have shape and durability requirements that rule out using a high percentage of anything that behaves/ looks like flints.
Wheel meet again, don't know where, don't know when...

Re: Flints and tyres
« Reply #27 on: January 07, 2019, 07:29:37 am »
having unexpectedly skidded on smooth concrete myself I think there are conditions under which the measured coefficients of friction do not apply. Clearly those responsible for this roadway thought likewise else they wouldn't have added the surfacing to it.

  As I said in the first instance this is an unusual surfacing which I have not seen more widely used (thank goodness).  If I had to describe the aggregate used in two words, I'd say it was 'shattered flints', any one of which might, once loose, be sharp enough to cut/puncture a bicycle tyre.

cheers

LittleWheelsandBig

  • Whimsy Rider
Re: Flints and tyres
« Reply #28 on: January 07, 2019, 07:46:23 am »
That sounds more like the grit used on bituminous roofing or to prevent an emulsion seal coat from being lifted up by construction traffic tyres.

Precast concrete panels are an extremely unusual way to construct a road surface (quite rare even on bridges), so probably best considered an experiment or aberration.
Wheel meet again, don't know where, don't know when...

Re: Flints and tyres
« Reply #29 on: January 07, 2019, 08:43:04 am »
not that I have any great knowledge in this field but I have never seen an aggregate like this before; it might well be meant for some other purpose, but I don't think it is the same stuff as appears on roofing felts.

 The added surfacing has only been applied in a few key areas but as for describing the roadway as 'an experiment or aberration' I think that is about right.

cheers

Re: Flints and tyres
« Reply #30 on: January 07, 2019, 01:38:08 pm »
At a guess it sound like some form of blast furnace slag as it a glassy aggregate that can be used in tarmac and concrete.

LittleWheelsandBig

  • Whimsy Rider
Re: Flints and tyres
« Reply #31 on: January 07, 2019, 01:56:23 pm »
I don't know of anybody using blastfurnace slag as aggregate in recent times; it is pretty valuable for other things. Ground Granulated Blastfurnace Slag (GGBS), fly ash (electrically precipitated from coal-fired power station smoke) and silica fume (from making ferro-silicon alloys) are all used as cement replacements when making concrete (replacing 25-85% of the cement content) with some quite handy performance enhancement, apart from the green benefits. The continuing reduction in blast furnaces, coal-fired power stations and steelmaking in the UK must significantly reduce the availability of these materials at some point.
Wheel meet again, don't know where, don't know when...