Building a recumbent trike rear wheel

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531colin
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Re: Building a recumbent trike rear wheel

Post by 531colin »

Chris Jeggo wrote: 18 Oct 2021, 5:54pm To get the rim in the same plane as the central plane of the bike frame the asymmetry of the dishing has to cancel out the asymmetry of the dropouts. Where the hub flanges finish up depends on the choice of hub. It therefore follows that the symmetry of the spoking depends on the choice of hub.
There are two desirable symmetries, the rim with respect to (wrt) the bike frame, and the rim wrt the hub flanges. If the frame builder knows the asymmetry of the hub flanges wrt the locknuts then he can build the frame to match, and everything will be lovely. Clearly ICE have designed their frame on the assumption that the central plane of the hub flanges is 6mm from the central plane of the locknut faces.
information is available for spoke length calculations

It must be at least 30 years ago that Orbit were building some frames with the dropouts 4mm to the right; that was a compromise between chainline and completely eliminating dish. I guess with a recumbent the chain is so long that chainline is less important, and they have gone for eliminating dish.
Even so, I think that its an unsound assumption that if you put the rim equidistant between the flanges then the rim will be on the bike's centreline, although it probably matters less on a long wheelbase trike than on a short wheelbase bike.
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Tilley
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Re: Building a recumbent trike rear wheel

Post by Tilley »

SJS built a wheel for my Trice TNT trike with a Sturmey Archer cassette hub and i didnt specify any specific dishing. The wheel has performed faultlessly for years so I cannot see that the adjustment will make a significant difference.
fullfathom5
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Re: Building a recumbent trike rear wheel

Post by fullfathom5 »

Thanks everybody who replied. SJS Cycles are now happy they understand my trike's specific requirements and I should be getting a new rear wheel in 3 to 4 weeks (although I won't need it for a while as I have also just sourced a brand new 9 speed 9-32 ICE cassette).

Interestingly, from browsing trike forums it appears that (as @tilley stated) it doesn't really seem to matter if a trike's back wheel is dished correctly or not .
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Tigerbiten
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Re: Building a recumbent trike rear wheel

Post by Tigerbiten »

It only really matters if you're going to fit 50-406 tyres due to the back fork being wide enough to fit anything smaller even if slightly offset.

Luck .......... :D
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531colin
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Re: Building a recumbent trike rear wheel

Post by 531colin »

If you are just bunging an odd wheel you happen to have kicking about then fair enough, why worry?
But if you are having a wheel handbuilt, and the frame designer worked it out so that you can have a dishless (reduced dish) wheel, then why not have a reduced dish wheel.....greater strength and reliability for no extra weight, whats not to like?

(I wonder which gets the greater side loading, the back wheel of a bike where the rider gets out of the saddle, or the back wheel of a tadpole recumbent trike, cornered enthusiastically?)
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Chris Jeggo
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Re: Building a recumbent trike rear wheel

Post by Chris Jeggo »

Many years ago I knew someone who was trying to design an electric recumbent trike and who wrote off at least one wheel while cornering. Also many years ago I knew several members of the Tricycle Association who habitually cornered enthusiastically, but on racing trikes, not tadpoles.
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[XAP]Bob
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Re: Building a recumbent trike rear wheel

Post by [XAP]Bob »

531colin wrote: 18 Oct 2021, 6:38pm It must be at least 30 years ago that Orbit were building some frames with the dropouts 4mm to the right; that was a compromise between chainline and completely eliminating dish. I guess with a recumbent the chain is so long that chainline is less important, and they have gone for eliminating dish.
Even so, I think that its an unsound assumption that if you put the rim equidistant between the flanges then the rim will be on the bike's centreline, although it probably matters less on a long wheelbase trike than on a short wheelbase bike.
Wheel doesn't need to be on the centreline at all, look at the wind cheetah.

The chainlink is basically not relevant with the longer chain, but possibly more importantly the forces on a trike wheel are fundamentally different from on a bike wheel. A bike leans into a corner, so the force is always acting vertically through the wheel; a trike doesn't, so there is a substantial lateral force where the wheel meets the road.
Since that force is applied in either direction (depending on which way you steer) the wheel really wants to be able to cope with those forces in both directions. A substantially dished wheel is less strong in one direction than the other.

It also helps that all the spokes end up the same length, one fewer spare part to carry.
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.
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NATURAL ANKLING
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Re: Building a recumbent trike rear wheel

Post by NATURAL ANKLING »

Hi,
531colin wrote: 20 Oct 2021, 11:38am If you are just bunging an odd wheel you happen to have kicking about then fair enough, why worry?
But if you are having a wheel handbuilt, and the frame designer worked it out so that you can have a dishless (reduced dish) wheel, then why not have a reduced dish wheel.....greater strength and reliability for no extra weight, whats not to like?

(I wonder which gets the greater side loading, the back wheel of a bike where the rider gets out of the saddle, or the back wheel of a tadpole recumbent trike, cornered enthusiastically?)
https://en.wikipedia.org/wiki/Red_Bull_Soapbox_Race
Plastic wheels seem to be favourite at the moment........they bend but appear not to break................
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Chris Jeggo
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Re: Building a recumbent trike rear wheel

Post by Chris Jeggo »

[XAP]Bob wrote: 21 Oct 2021, 2:18pm ... A bike leans into a corner, so the force is always acting vertically through the wheel...
Not always; not
531colin wrote: 20 Oct 2021, 11:38am where the rider gets out of the saddle.
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squeaker
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Re: Building a recumbent trike rear wheel

Post by squeaker »

Chris Jeggo wrote: 21 Oct 2021, 5:39pm
[XAP]Bob wrote: 21 Oct 2021, 2:18pm ... A bike leans into a corner, so the force is always acting vertically through the wheel...
Not always; not
531colin wrote: 20 Oct 2021, 11:38am where the rider gets out of the saddle.
Occasionally with interesting results
FrontWheelFold.jpg
"42"
Psamathe
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Re: Building a recumbent trike rear wheel

Post by Psamathe »

squeaker wrote: 21 Oct 2021, 5:57pm
Chris Jeggo wrote: 21 Oct 2021, 5:39pm
[XAP]Bob wrote: 21 Oct 2021, 2:18pm ... A bike leans into a corner, so the force is always acting vertically through the wheel...
Not always; not
531colin wrote: 20 Oct 2021, 11:38am where the rider gets out of the saddle.
Occasionally with interesting resultsFrontWheelFold.jpg
Which maybe illustrates why some riders are better suited to recumbents?

Ian
Jdsk
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Re: Building a recumbent trike rear wheel

Post by Jdsk »

Which force is being discussed here?

Thanks

Jonathan
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[XAP]Bob
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Re: Building a recumbent trike rear wheel

Post by [XAP]Bob »

Intuition suggests to me that cornering forces are likely to be greater than the relatively minor component of power which ends up perpendicular to the plane of the wheel.

Going round a ten metre diameter circle at 20mph requires a centripetal force of ~1600N for a 100kg load.
That's fairly significant - pushing sideways with the (earth normal) weight of 160kg - and that is applied at the height of the hub.

A cyclist getting out of the saddle and throwing the bike back and forth is doing so to line up the downward force on the pedals with the line intersecting the two contact patches (approximately).
That's going to be a relatively small angle, 15 degrees or so, thus applying a lateral force of 1/4 of the downwards input. Chris Hoy might manage to put 6 times his body weight through the pedals I suppose.
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.
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