Front Wheel Drive?

[oncemore]

I know TW Bents are quite well established - but what is the reasoning behind front wheel drivers?

Cobra Folding Recumbent Bicycle bike Lightweight Frame on eBay (end time  02-Sep-09 13:40:52 BST)

Same seller seems to have at least two models of folding trikes - at what seem good prices.

[PhilO]

I know TW Bents are quite well established - but what is the reasoning behind front wheel drivers?

Cobra Folding Recumbent Bicycle bike Lightweight Frame on eBay (end time  02-Sep-09 13:40:52 BST)

Same seller seems to have at least two models of folding trikes - at what seem good prices.

Pros: Shorter chain
         Less steering interference if the bike is a low racer
         Separable frame design is relatively easy
Cons: steering interfence greater on higher bike designs (chain twist)
          Grip can be compromised when climbing
          Heel clearance to derail  dueraileur  gear mech. can be an issue.
           Pedal-induced steering can be a problem (but I've not been able to detect it on the few I've ridden).

I'm sure there are others, and people will be along shortly to add them! 

[Regulator]

Bidding for that ends the day before my birthday...

...if anyone's feeling generous 

[oncemore]

Does the boom on which the cranks sit move with the forks (in which case presumably the distance to the pedals alters) or is it fixed in line with the frame (in which case I assume the chain must twist)?

I had a "normal" TW Bents for a while - it was certainly top vfm as 'bents go!

[Von Broad]

Does the boom on which the cranks sit move with the forks (in which case presumably the distance to the pedals alters) or is it fixed in line with the frame (in which case I assume the chain must twist)?

Yes, that's right, the boom is fixed in line with the frame - the most common type of recumbent.

Conversely, you can get the former type which you describe - a moving bottom bracket, FWD. Look at this as an example of fine workmanship.

I did have a go at building one [not quite to that standard!]. I finished it and rode it once round a car park. It was a nightmare! It had so much pedal steer it was frightening. But people do ride them.....on the roads.

There was a chap [his name escapes me now] who rode a homemade dual 700c MBB FWD on PBP. He seemed to do ok. I was well impressed. Got round quicker than me anyway.  

If you could perfect that kind of geometry, and could master the handling, the MBB solves a primary compromise of RWD recumebents - that long floppy chain.

Another moot point, but drive traction can be a problem with FWD, particularly when ascending wet slippery conditions. But again, some people don't seem to have a problem with this.

edit: here's another example of the MBB FWD - this one using larger wheels. For some reason it's the French that are getting into these designs at the moment. 

[oncemore]

The big wheeler is good, but the one in the first link is simply STUNNING. The best looking two wheeler sans engine I've ever seen. Phenomenal. Words fail...except oh how I want one!!

[Jon P]

I've ridden a Toxy ZR for a couple of years, not massively impressed with FWD compared to RWD, but it works.  The "magical mechanism" which "allows the chain to twist" doesn't really exist, as on this bike it's just a couple of idlers and a chain 1.5 or 2x the normal length.  What it means in practice is that you are severely hampered eg coming out of a T-junction, it often is easier just to get off the bike and move it by hand, the steering is extremely restricted but works well enough on the open road but would be a pain negotiating tight bends eg on an audax.

The front wheel tends to slip on hills, I recently got up Edge Hill on mine which must be 1:5 in places but it will start going at 1:8 in the wet, and when the surface is bumpy you always get a bit of intermittent slip.

I got round the heel interference by installing a 3cm shim on the right pedal, not ideal but has been OK so far.

All-in-all a bent for £1200 that weighs 12kg and is a folder is a good buy, I'd go for it on its own merits and just looking for a link I saved for a Berlin bikeshop that was selling one that weighed 15kg and cost a lot more, now vanished ...

[rogerzilla]

A FWD trike would presumably be less of a problem.  Chain drive to differential (if you bother with one), driveshafts with CV joints to wheels.  No efficiency problems, but I imagine it would be terrifically heavy.

[LittleWheelsandBig]

A FWD trike would presumably be less of a problem.  Chain drive to differential (if you bother with one), driveshafts with CV joints to wheels.  No efficiency problems, but I imagine it would be terrifically heavy.

The Russians have gone this way.  Peter Eland of VeloVision had one years ago(may still do so).

[Mr Larrington]

Look at this as an example of fine workmanship.

Drool.  I am hugely in lust with Le Rapide...

[Jon P]

Mr L just reminded me of another gripe about FWD - one of his friends can bring the chain off just by pedalling backwards, and mine comes off the forward idler regularly for apparently no reason whatever and I need to split the chain to get it back on, I just can't understand how it does it.

[TimO]

There was a FWD trike some years back (single front wheel, twin rear wheels), where the hub had some very clever universal joint arrangement, so that the pedals and chain were fixed, but the front wheel could steer.

I've got a piccy somewhere, but I don't think it shows the details of the hub, since it was all hidden inside the hub/wheel and not visible.

[rogerzilla]

There's a thought - do you actually *need* handlebars on a FWD trike or bike?  Just somewhere to put the gear and brake levers.

[Wendy]

There's a thought - do you actually *need* handlebars on a FWD trike or bike?  Just somewhere to put the gear and brake levers.

Many FWDs do need handlebars, since apart from FWD they still have a std headset and steering.

[TimO]

There's a thought - do you actually *need* handlebars on a FWD trike or bike?  Just somewhere to put the gear and brake levers.

You could go the Flevo bike route, the wheel and chain don't move relative to each other, and the handlebars don't steer the bike, they're purely somewhere to rest your hands and fit the controls to.

[Panoramix]

The big wheeler is good, but the one in the first link is simply STUNNING. The best looking two wheeler sans engine I've ever seen. Phenomenal. Words fail...except oh how I want one!!

Don't underestimate Breton engineering 

The factory is close to places where they build maxi multihulls racing boats or high tech windsurfs using a similar technique (prepeg carbon). I wouldn't be surprised if a bit of technology transfer happened! I am not sure how much they cost but I wouldn't mind one!