How straight does a frame been to be?

[rogerzilla]

When discussing wheel alignment specifically, either spelling is used in the UK, "caster" being more popular, and universal in the US. The front wheels on supermarket trolleys are normally castors in the UK.

I think the "e" spelling is popular in wheel alignment circles because it matches "camber".

[CJ]

in my dictionary it says 'caster -person or thing that casts'

are you sure you don't mean 'castor' ?
(Although that is how Americans tend to spell it, bless 'em.....)

Sorry, maybe I've been corresponding too much lately with Americans!

My Concise Oxford Dictionary nevertheless lists '1 var. of CASTOR' as the most familiar and important meaning of 'caster' - and without any (US) indication that it's a purely or mainly American variant. Person who casts and machine for casting type come in at 2 and 3 respectively. So I think most people will get it.

[hoogerbooger]

(My Raleigh Randonneur is out by a similar amount between the chainstays.... but I have a 130 wheel in 126 drop-outs and I think the dimple on the chainset side weakens it laterally....so that one has moved more........

as it seems to ride fine.....with or without hands on the bar.....I've just not got round to cold setting it.....)

[531colin]

(My Raleigh Randonneur is out by a similar amount between the chainstays.... but I have a 130 wheel in 126 drop-outs and I think the dimple on the chainset side weakens it laterally....so that one has moved more........

as it seems to ride fine.....with or without hands on the bar.....I've just not got round to cold setting it.....)

Yes, the right side chainstay is usually less stiff because its dented to clear the chainring; cold setting is best done one side at a time, if you do both together it usually ends up less than straight.

[pjclinch]

"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.

Sorry I've not got round to this, keep meaning to take photos and forget, but in ~20 years of using it I've never even suspected the wheels aren't vertical. The rear is just set to the side of the main frame spar. while the front is on the centreline. Will try and remember to take pics...

Pete.

[531colin]

...............My Burrows 8-Freight cargo bike ....... 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 may or may not have much trail, but it would certainly have less trail if the fork were offset conventionally. https://en.wikipedia.org/wiki/Bicycle_a ... e_geometry

[pjclinch]

"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?

Here's some pics, any attempt to rotate the original doesn't seem to affect them being sideways here, sorry!
The dry road thing was a bit hard to organise and will have to wait, but I don't think there's any attempt to be clever by canting the wheels.

I think some account needs to be made for a rider's ability to correct for such oddities. Given that balancing a bike to start with requires a lot of unconscious adjustment of balance and position I suspect I just dial in to the oddness and correct, much as for example riding a bike along a strong camber and not drifting down it, or riding with one pannier and not being pulled to one side, and so on.
The first time I rode a Kettwiesel trike with only a right-hand driven wheel was on a heavily cambered road. I spent several minutes drifting in to the kerb. Once I'd learned to correct for that it became a non-issue, but that's simply a learning fix, not an engineering one.

Pete.

[Jdsk]

IMG_20240215_113920588_HDR.jpg (68.34 KiB) Viewed 808 times

[Brucey]

I always thought it didn't look right but I was too polite to say anything to his face. The 8-freight design is a fine effort, but they are certainly not without their problems; in particular, the Al chassis tends to crack badly in hard use, which is an ongoing problem for many users. I think a steel chassis would be much easier to repair.

[pjclinch]

I always thought it didn't look right but I was too polite to say anything to his face. The 8-freight design is a fine effort, but they are certainly not without their problems; in particular, the Al chassis tends to crack badly in hard use, which is an ongoing problem for many users. I think a steel chassis would be much easier to repair.

It would be, but it would also be much harder to pick up!
One of the USPs of the 8-Freight is it's remarkably easy to manhandle compared to just about anything else of comparable capacity. I can pick it up in balance unladen with two fingers.

Mine has easy access to its parking spot now, but in its previous parking spot it had to be picked up and carried up some narrow steps through a standard sized door. That was a faff but certainly not untenable, it would be pretty much a non-starter with a Bakfiets.

As with most lightweight kit it's not ideal for heavy use and that's not surprising. I typically use mine for loads of less than 20Kg and where big loads are characterised by bulk more than weight, for which it's proved strong enough (touchwood!) for ~ 20 years now. If you're carrying significantly more on a regular basis I'd strongly suggest something meatier in construction and e-assistance too.

But we digress from the point somewhat, that being that bikes can be workable even when they "don't look right".

Pete.

[Brucey]

The 8-feight weighs what, ~35lbs or so. I don't for a moment doubt that a stronger steel chassis would probably be heavier too, but if the weight crept over 40lbs (say) then I'd suppose that we might have gone wrong somewhere. Local to me a courier firm used a small fleet of 8-freights, I guess they usually had an insurance-mandated load bin fitted, which probably weighed ~10kg even when it was empty. At a guess, the average load must have been 39-40kg;ex-depot, anyway, whatever it was, it turned out to be quite enough to crack every single one. I carried out a straw poll of the rider's concerns, and typically the cracking was prominent. But they seemed to much less concerned by the steering,which probably shows you can get used to anything. I see people happily riding bent bikes of all kinds all the time but I'd probably take umbrage if someone tried to sell me one.

[CJ]

The first time I rode a Kettwiesel trike with only a right-hand driven wheel was on a heavily cambered road. I spent several minutes drifting in to the kerb.

That's correctly designed for its home market, driving and riding on the right, where the lower wheel helps to drive the machine back up the camber, couter-acting the effects of gravity, trail and tilt upon the steering. For the same reason most traditional British tricycles drove the left wheel only. Riders who took their English 'barrow' on the 'continong' came back with arm-ache from the constant steering torque required to keep out of the ditch!

[pjclinch]

The first time I rode a Kettwiesel trike with only a right-hand driven wheel was on a heavily cambered road. I spent several minutes drifting in to the kerb.

That's correctly designed for its home market, driving and riding on the right, where the lower wheel helps to drive the machine back up the camber, couter-acting the effects of gravity, trail and tilt upon the steering. For the same reason most traditional British tricycles drove the left wheel only. Riders who took their English 'barrow' on the 'continong' came back with arm-ache from the constant steering torque required to keep out of the ditch!

I'm aware of that, the point is steering counter to camber is a learnable response, just as other imbalances are. Learning a different response takes time, but it's quite possible, which is how tadpole trikes get ridden fine on cambered roads despite not having a tendency to be corrected by the "downhill" drive.

Pete.

[pjclinch]

The 8-feight weighs what, ~35lbs or so. I don't for a moment doubt that a stronger steel chassis would probably be heavier too, but if the weight crept over 40lbs (say) then I'd suppose that we might have gone wrong somewhere. Local to me a courier firm used a small fleet of 8-freights, I guess they usually had an insurance-mandated load bin fitted, which probably weighed ~10kg even when it was empty. At a guess, the average load must have been 39-40kg;ex-depot, anyway, whatever it was, it turned out to be quite enough to crack every single one. I carried out a straw poll of the rider's concerns, and typically the cracking was prominent. But they seemed to much less concerned by the steering,which probably shows you can get used to anything. I see people happily riding bent bikes of all kinds all the time but I'd probably take umbrage if someone tried to sell me one.

This pretty much makes my point: the steering on an unashamedly off-centre bike can be gotten used to quite easily if the designer has done a proper job on the design as a whole: MB did.
That you'd prefer something else is a legitimate choice, of course, but matters of material choice and whether the frame is up to heavy duty professional use are somewhat moot when the question is whether it's easy enough to steer. It is.

I'm not trying to set up the 8-Freight as some paragon of design perfection, I'm using it as an example that a few millimetres outside of some notional perfect track may not necessarily be a Biggie, nothing more than that.

Pete.

[Brucey]

i understand entirely.MB wasn't perfect and nor were many of his designs. But at least he got the 8-freight out there; by contrast I am more than slightly worried that some of my best ideas will die with me.