How straight does a frame been to be?

[pjclinch]

A zombie thread... Back at the time the roads were soaked 24/7 so I couldn't take the photo and then I forgot about it, but it popped in to my head on the way home...

"Common sense" says you want everything in a perfect line.

My Burrows 8-Freight cargo bike doesn't even bother trying and has the rear wheel sat to one side of the main frame spar, so is several centimetres off-beam from the front. It doesn't really ride no-hands too well (!), but then with an 80 degree head angle and a 20" wheel on a dead-straight fork giving only marginally more than no steering trail at all, it's probably that more than the offset back wheel... The very long wheelbase will affect the end result, I imagine, but overall my takeaway is judge by the actual ride (actually fine on the 8-Freight unless you have rather silly loads on board) and not the ruler.

I thought Burrows designed the 8-freight's frame and fork so that one or other (perhaps both) of its wheels stood at a non-vertical angle to the road, so they tracked in-line despite being offset by several centimetres at the hub. What kind of straight-line tracks does this bike leave after going through a puddle on a dry road: two wavy lines side-by-side, or weaving symmetrically around one another, or something in-between that weaves loosely with only occasional and unequal crossings?

Two neat parallel tracks...

8 Freight tracks

Pete.

[Brucey]

that is an interesting picture; I suppose the long wheelbase must spare it the worst effects of crabbing; I strongly suspect that, with a shorter wheelbase, the rear tyre would scrub out rather quickly.

[Carlton green]

I read a study on wheelchairs where they tested wheel misalignment and they concluded that as you increase toe in or toe out of the wheel the rolling resistance increases exponentially. And just 1 deg of toe in or out produced a 25% increase in rolling resistance. I would say that was quite significant, especially at the speeds of average cyclist where aerodynamics has less of an impact

It’s maybe off of topic so I hope that nobody will mind the (ideally brief) diversion. I was shocked at that increase in rolling resistance and wondered how it translated across to (two wheel) bike trailers. Is that study, or similar data, available to read on-line? Thank you.

[pjclinch]

that is an interesting picture; I suppose the long wheelbase must spare it the worst effects of crabbing; I strongly suspect that, with a shorter wheelbase, the rear tyre would scrub out rather quickly.

This is my assumption too, though that'll be "for some values of 'shorter'". For example, Burrows' Ratracers/Ratcatchers look like they use a similar offset wheel to save the bother of splitting the main frame spar, are considerably shorter wheelbase than an 8-Freight and they were built and used for HPV racing where rubbish handling and a tendency to crash when cornering are not desirable features!

I've no idea what the critical numbers will be, but the Ratracer suggests at least a bit lower than an 8-Freight's wheelbase.

Pete.

[colin54]

[CJ]

that is an interesting picture; I suppose the long wheelbase must spare it the worst effects of crabbing; I strongly suspect that, with a shorter wheelbase, the rear tyre would scrub out rather quickly.

I read a study on wheelchairs where they tested wheel misalignment and they concluded that as you increase toe in or toe out of the wheel the rolling resistance increases exponentially. And just 1 deg of toe in or out produced a 25% increase in rolling resistance. I would say that was quite significant, especially at the speeds of average cyclist where aerodynamics has less of an impact

It’s maybe off of topic so I hope that nobody will mind the (ideally brief) diversion. I was shocked at that increase in rolling resistance and wondered how it translated across to (two wheel) bike trailers. Is that study, or similar data, available to read on-line? Thank you.

Since a bicycle is, uniquely, composed of two castors with a common pivot, any sideways force on a tyre tends to swing that tyre into line with the other one. What little "crabbing" there may nevertheless be, is sustainable only by the rider maintaining a constant steering torque between the two castors. The fact that people seldom notice this torque indicates that the amount of tyre scrub and energy absorbed by it must be very small. I would guess that even with the amount of misalignment seen in the 8-freight, any scrub is immeasurably insignificant compared to that caused by the sideways forces of cornering, which are themselves demonstrably less than the force and rear tyre wear entailed in propelling the bicycle forwards.

Vehicles with wheels that run in fixed alignment side-by-side, on the other hand, cannot compensate for any misalignment except by scrubbing their tyres, which they do, to great and dire effect if the misalignment is at all significant.

The bicycle is indeed a most wonderful invention.

[pjclinch]

The bicycle is indeed a most wonderful invention.

Amen!

[531colin]

Will an 8 freight go no hands?

On a regular touring type bike, having the back wheel 4 mm to one side of the front wheel means riding no hands with the saddle under one cheek to go straight ahead.
(Why 4mm? Because that was what I had…some Orbit bikes had the frame offset 4mm in order to reduce wheel dish, so I tried the “wrong” combinations; it would have been rude not to!)

[brumster]

Will an 8 freight go no hands?

On a regular touring type bike, having the back wheel 4 mm to one side of the front wheel means riding no hands with the saddle under one cheek to go straight ahead.
(Why 4mm? Because that was what I had…some Orbit bikes had the frame offset 4mm in order to reduce wheel dish, so I tried the “wrong” combinations; it would have been rude not to!)

Interesting. I once test rode a Genesis Tour de Fer one time and found it almost impossible to steer ' no-handed' Never an issue on other Touring bikes I've either owned or ridden.

[pjclinch]

Will an 8 freight go no hands?

On a regular touring type bike, having the back wheel 4 mm to one side of the front wheel means riding no hands with the saddle under one cheek to go straight ahead.
(Why 4mm? Because that was what I had…some Orbit bikes had the frame offset 4mm in order to reduce wheel dish, so I tried the “wrong” combinations; it would have been rude not to!)

Not really, or at least not for me. I can ride no-hands but I'm not great at it, and I do find it varies a lot between bikes. The MTB is no great trouble, the Moulton limited to short distances (couple of hundred meters or so) the Brompton even shorter distances and the 'bent I just don't want to try (though I've come across the same model ridden no-hands).

The one time I got a significant distance on the 8F no hands was really quite an odd experience as it veered from side to side far more than most hands-free. I do wonder if that has more to do with the 80 degree head angle than the unusual wheel alignment though. There wasn't an obvious bias in either direction as I remember it, and I also note there's apparently some ingrained bias to a lot of my no-hands, so the Brompton significantly often veers right when I lose the line, irrespective of which side of the camber I'm on.

Pete.

[531colin]

............
Interesting. I once test rode a Genesis Tour de Fer one time and found it almost impossible to steer ' no-handed' Never an issue on other Touring bikes I've either owned or ridden.

Yes, but I recognise 3 categories of "impossible no hands"
1.. Very stable steering, so the bike goes where its heading and needs lots of effort to turn
2.. the polar opposite....think of somebody winning a race (or stage) crossing the line and with their hands still in the air slalom-ing the photographers and team people .....this requires quick steering, and even quicker reflexes
3.. something off-track....sometimes can be ridden no hands with the saddle under one cheek

[531colin]

Will an 8 freight go no hands?

On a regular touring type bike, having the back wheel 4 mm to one side of the front wheel means riding no hands with the saddle under one cheek to go straight ahead.
(Why 4mm? Because that was what I had…some Orbit bikes had the frame offset 4mm in order to reduce wheel dish, so I tried the “wrong” combinations; it would have been rude not to!)

Not really, or at least not for me. I can ride no-hands but I'm not great at it, and I do find it varies a lot between bikes. The MTB is no great trouble, the Moulton limited to short distances (couple of hundred meters or so) the Brompton even shorter distances and the 'bent I just don't want to try (though I've come across the same model ridden no-hands).

The one time I got a significant distance on the 8F no hands was really quite an odd experience as it veered from side to side far more than most hands-free. I do wonder if that has more to do with the 80 degree head angle than the unusual wheel alignment though. There wasn't an obvious bias in either direction as I remember it, and I also note there's apparently some ingrained bias to a lot of my no-hands, so the Brompton significantly often veers right when I lose the line, irrespective of which side of the camber I'm on.

Pete.

Most small-wheel bikes fall into the "difficult to ride no-hands due to quick steering" category above.
I had a go on one of Steve Mundie's small wheelers https://www.steve-mundie.co.uk/ ....literally went up the road, came back no hands, so it is possible to build a small wheeler that rides well no hands, I guess Moulton and Brompton can't be bothered to find out how to do it.

8 freight veering sounds like wheel flop due to long trail rather than having to lean the bike (saddle under one cheek) to get the wheels in line.

[pjclinch]

I had a go on one of Steve Mundie's small wheelers https://www.steve-mundie.co.uk/ ....literally went up the road, came back no hands, so it is possible to build a small wheeler that rides well no hands, I guess Moulton and Brompton can't be bothered to find out how to do it.

The easiest bike to ride no-hands I've tried was a Dutch hire bike (quite possibly an OV-fiets). It was nice riding along on a cold day with my hands in my pockets, but it's not really high on my overall list of priorities.
I suspect it's not really on Moulton or Brompton's list of priorities either, for that matter, but also the fact that I, a not-very-good hands free rider, can ride them for a bit no-hands in any case suggests they're not appallingly compromised in that respect.

I do know that no-hands ability varies a lot. My wife is much better at it than me on an identical bike, for example (though I can ride a unicycle a bit and she can't at all). Quite a few folk just can't/won't, so that you rode one of Mundie's easily may say more about you than about how good/bad a Moulton/Brompton is in that respect.

Pete.

[531colin]

I had a go on one of Steve Mundie's small wheelers https://www.steve-mundie.co.uk/ ....literally went up the road, came back no hands, so it is possible to build a small wheeler that rides well no hands, I guess Moulton and Brompton can't be bothered to find out how to do it.

The easiest bike to ride no-hands I've tried was a Dutch hire bike (quite possibly an OV-fiets). It was nice riding along on a cold day with my hands in my pockets, but it's not really high on my overall list of priorities.
I suspect it's not really on Moulton or Brompton's list of priorities either, for that matter, but also the fact that I, a not-very-good hands free rider, can ride them for a bit no-hands in any case suggests they're not appallingly compromised in that respect.

I do know that no-hands ability varies a lot. My wife is much better at it than me on an identical bike, for example (though I can ride a unicycle a bit and she can't at all). Quite a few folk just can't/won't, so that you rode one of Mundie's easily may say more about you than about how good/bad a Moulton/Brompton is in that respect.

Pete.

Has it occurred to you that I have ridden Brompton and Moultons?

[Brucey]

............
Interesting. I once test rode a Genesis Tour de Fer one time and found it almost impossible to steer ' no-handed' Never an issue on other Touring bikes I've either owned or ridden.

Yes, but I recognise 3 categories of "impossible no hands"
1.. Very stable steering, so the bike goes where its heading and needs lots of effort to turn
2.. the polar opposite....think of somebody winning a race (or stage) crossing the line and with their hands still in the air slalom-ing the photographers and team people .....this requires quick steering, and even quicker reflexes
3.. something off-track....sometimes can be ridden no hands with the saddle under one cheek

I'd add a fourth category; bikes with defective headsets.


Incidentally, do you know what steering geometry Steve Mundie used?