rear wheel steering
rear wheel steering
I know it's been tried before and generally not well received. I'll go and try and google out what I can over the next few days, but I have a cunning plan for a vehicle in my head that involves rear wheel steering and I'm trying to work out what makes it so damned bad.
After all Thrust SSC used it (fairly small turning angle though), and did the 1/3 scale mini they used for testing (on UK roads no less)
So why is is so hard? What goes wrong?
After all Thrust SSC used it (fairly small turning angle though), and did the 1/3 scale mini they used for testing (on UK roads no less)
So why is is so hard? What goes wrong?
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.
There are two kinds of people in this world: those can extrapolate from incomplete data.
Re: rear wheel steering
Essentially the problem (as I understand it) is that once the nose gets out of line it then tries to turn more and more . If you ever tried to push a trolley with fixed wheels on the front and castors at the back, you'd see what I mean. You end up fighting the thing, it's unstable directionally.
Re: rear wheel steering
Think the other issue (and more significant for mosy cycles) is balance.
Normally you lean left, and steer left (throwing your weight right) to correct - making an inherently stable dynamic system.
RWS your weight is thrown the wrong way (at least initially) so they are inherently unstable.
Of course as I'm not aiming for two wheels this is less important, and there do seem to be a number of RWS trikes around, some commercial ones even.
Normally you lean left, and steer left (throwing your weight right) to correct - making an inherently stable dynamic system.
RWS your weight is thrown the wrong way (at least initially) so they are inherently unstable.
Of course as I'm not aiming for two wheels this is less important, and there do seem to be a number of RWS trikes around, some commercial ones even.
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.
There are two kinds of people in this world: those can extrapolate from incomplete data.
- corshamjim
- Posts: 290
- Joined: 17 Jan 2010, 7:31pm
- Location: Corsham, Wiltshire
Re: rear wheel steering
I think another problem is that if you find yourself travelling parallel to and close to the kerb, if you try steering away from the kerb your back wheels will hit it. Or worse you're travelling parallel with an HGV.
ToggleChain Tourist - http://www.togglechaintour.co.uk/
Re: rear wheel steering
The biggest issue is stability at speed, should you oversteer & then try to correct it.
Forklift trucks are usually rw steer and can tip easily, watch this clip: http://www.youtube.com/watch?v=x79Ys8p4mOY&feature=related
Once you start cornering, if you overcook it & the truck begins to tip over, there is nothing you can do to correct it. The steering is useless, and either accelerating or hitting the brakes will just make it tip over even quicker, hence the rollcages & seatbelts they are all fitted with.
I remember watching a documentary about Thrust SSC & the Mini they used. I'm pretty sure they got around the problem by using a tadpole layout, but with a pair of rear wheels one behind the other - they both steered, and the geometry allowed them to self-centre. Using one rear wheel would just suffer the same problem of having two rear wheels side by side.
Anyway, what's your idea? Would the above help, or would it be too long?
Edited: Bad grammar yet again.
Forklift trucks are usually rw steer and can tip easily, watch this clip: http://www.youtube.com/watch?v=x79Ys8p4mOY&feature=related
Once you start cornering, if you overcook it & the truck begins to tip over, there is nothing you can do to correct it. The steering is useless, and either accelerating or hitting the brakes will just make it tip over even quicker, hence the rollcages & seatbelts they are all fitted with.
I remember watching a documentary about Thrust SSC & the Mini they used. I'm pretty sure they got around the problem by using a tadpole layout, but with a pair of rear wheels one behind the other - they both steered, and the geometry allowed them to self-centre. Using one rear wheel would just suffer the same problem of having two rear wheels side by side.
Anyway, what's your idea? Would the above help, or would it be too long?
Edited: Bad grammar yet again.
- hubgearfreak
- Posts: 8212
- Joined: 7 Jan 2007, 4:14pm
Re: rear wheel steering
[XAP]Bob wrote:I have a cunning plan for a vehicle in my head that involves rear wheel steering
just 'cos common sense says otherwise, doesn't mean you shouldn't go for it.
gallileo springs to mind
Re: rear wheel steering
Swizz69 wrote:The biggest issue is stability at speed, should you oversteer & then try to correct it.
Ah - that'd be bad, although it's unlikely to be truly high speed...
I remember watching a documentary about Thrust SSC & the Mini they used. I'm pretty sure they got around the problem by using a tadpole layout, but with a pair of rear wheels one behind the other - they both steered, and the geometry allowed them to self-centre. Using one rear wheel would just suffer the same problem of having two rear wheels side by side.
Anyway, what's your idea? Would the above help, or would it be too long?
Hmm - so the pair of wheels at the back stabilised each other - hmm, I think that would be too long for me, but it did show that RWS is plausible.
I am looking at a tadpole configuration, so kerb crawling isn't a problem - close HGVs would be more of an issue, but they tend to be good round here.
I'm thinking about a clean, social, recumbent tandem (i.e. a side by side 'bent tandem with enclosed chainlines). In order to make the chainlines relatively short and easy to keep out of the way and clean I was looking at dual independent front wheel drive, and therefore using a single steering rear wheel.
There must be a dozen configurations which could work well, but I know Mrs Bob isn't going to be keen on a very low machine in traffic ...
...tbc.
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.
There are two kinds of people in this world: those can extrapolate from incomplete data.
Re: rear wheel steering
I think the thing is RWS can be done but it has more 'issues' with it than FWS.
"I thought of that while riding my bike." -Albert Einstein, on the Theory of Relativity
2007 ICE QNT
2008 Hase Kettwiesel AL27
2011 Catrike Trail
1951 engine
2007 ICE QNT
2008 Hase Kettwiesel AL27
2011 Catrike Trail
1951 engine
- 7_lives_left
- Posts: 798
- Joined: 9 May 2008, 8:29pm
- Location: South Bucks
Re: rear wheel steering
[XAP]Bob wrote:I am looking at a tadpole configuration, so kerb crawling isn't a problem - close HGVs would be more of an issue, but they tend to be good round here.
That reminds me of when I came across a very long flatbed lorry with front and rear wheel steering while cycling through London. It had very prominent notices warning following vehicles that this was the case. Having seen it in motion around a roundabout I can understand why the warning was present. You wouldn't want to get along side any HGV but the same would apply to this vehicle in spades.
What's the relevance to a rear wheel steering bicycle? It might be just as confusing to following vehicles as this lorry was. They might end up driving over you back wheel as you make a turn.
Re: rear wheel steering
Then they'd have been hitting you anyway...
Might be worth putting an RWS warning on the back though...
Might be worth putting an RWS warning on the back though...
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.
There are two kinds of people in this world: those can extrapolate from incomplete data.