DIY recumbent bike....?

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Brucey
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DIY recumbent bike....?

Postby Brucey » 1 Jun 2015, 1:08pm

Well.... where to begin....?

I think it is fair to say that I am a life-long rider of 'normal' bicycles. Out of curiosity, I have tried recumbents in the past, and of course if you wish to go as quickly as possible, a low-slung recumbent position appears to be almost obligatory. But until recently the idea of owning such a machine did not appeal to me; they were for the most part expensive oddball machines, lacking in basic practicality.

Of particular concern is the perceived (certainly, if not actual, always) problem that a low slung machine may be missed by other road users. Having ridden a motorcycle for many years, I know all about that... and I know that the average motorist is looking out for other cars first, (lorries and buses too) slow-moving normal bicycles (if you are lucky) and then a third 'other' category. Rightly or wrongly, there is a perception that 'not being seen' may truly be a matter of oversight if you are riding a low-slung machine.

In the long term I have all kinds of mad ideas about much faster machines, but in the shorter term I realised that I would need a machine that I could use (much as I use an normal bike) with a recumbent position, just to train on and try a few ideas out. I looked at those you can buy and they seemed expensive (for what they are), mostly with a riding position that is lower than I'd like, and not particularly amenable to being messed about with.

So I decided to build my own '(very) high racer recumbent' machine.... starting with a motley assortment of knackered mountain bikes, and a few other odds and ends, I have built this;

Image00016.jpg
best question so far; 'is it a chopper, mate?'


Now the saddle is a lash-up... but this machine has 700C wheels and the seat height is much like that of a normal bike. When stopped, you can straddle the machine but only if the lowest part of the saddle is narrow enough to go between your legs. ( I still don't know if I will ever come to a happy compromise in this respect; all constructive suggestions welcome).

At first, I couldn't ride the thing at all, and I was seriously worried that I'd built something unrideable. But since then I've stuck with it and I've (over a period of about a week and forty-odd miles) become vaguely competent with it.

Image00032.jpg
a rare sight!


In terms of the design objectives, although it is early days yet, it appears to have worked, in that I have yet to have any close passes whilst riding it. I think that the high riding position may really be helping to make the machine more visible to other road users. The sight of pedals flailing round at about eye level (for car drivers) certainly seems to give them pause for thought!

I've installed a SA 3 hub as a mid-drive, with an 11-28T 9s cassette. As configured presently it is approximately like having 45, 60, 80T chainrings, but that can easily be adjusted to give 29, 39, 52T instead. This setup gives instant access to low gears for starting (essential, I have found) and the drive can be easily reconfigured for touring or fast road work. As well as other cassettes at the rear I can replace the 3s hub with a 5s one easily enough, and indeed the mid-drive mountings will even accept a derailleur system up to 135mm wide. Thus a double derailleur system could give me (say) 6 x 9 gears. The front chain cannot come off, and the rear chain has yet to unship whilst riding the machine, even though I have not implemented the provision for chainguides. The whole drive is very quiet in use, and since most of the use can be in gear 2, and the chain runs are on large sprockets with straight runs, I would hope it is quite efficient, too.

So far as practicality goes, it is a yard and a half from the pedals to where you can put your feet down; I have found that sitting upright, unclipped, legs dangling, is the best way to approach tricky junctions, provided you can coast through them or intend to stop anyway. The steering is weird (to me) having a slight tiller component, and so far I can turn in about a 25 foot circle, feet up and pedalling; with practice I'd expect to get better than this. High speed handling remains a mystery to me; I've yet to venture over 25mph on it.

Although I hadn't exactly planned it, I have found that I can easily attach my carradice saddlebag to the rear of the seat, so I've already been able to use the machine for some utilitarian purposes. However I shan't use it too much more until I have made a better saddle arrangement.

All comments welcome!

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

beardy
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Re: DIY recumbent bike....?

Postby beardy » 1 Jun 2015, 1:24pm

A new class. The recumbent tall-bike class.

It will never get type approval with two kicking feet and a spinning toothed blade at face height. :shock:

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[XAP]Bob
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Re: DIY recumbent bike....?

Postby [XAP]Bob » 1 Jun 2015, 1:34pm

nice, although you've found the issue with such a high seat - stopping (or rather staying upright when stopping)

I too like the idea of a mid drive, sensible ranges of gears enabled with a minimum of fuss. Are you using one of the 'commonly' available trike drive hubs, or have you fashioned your own output sprocket?
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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Spinners
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Re: DIY recumbent bike....?

Postby Spinners » 1 Jun 2015, 1:47pm

Chapeau!

I'm seriously impressed with your fabrication of this beast and think it looks cool!
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mercalia
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Re: DIY recumbent bike....?

Postby mercalia » 1 Jun 2015, 3:36pm

I wouldnt like being that high off the ground on my back incase of a fall - a long way to fall and do your back in? there must be a reason that bents are low?

Brucey
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Re: DIY recumbent bike....?

Postby Brucey » 1 Jun 2015, 3:53pm

I have fitted a chainguard to the machine (cost = zero, it was an old chainring) because I was worried about disembowelling people. Mind you, with an IGH mid-drive, the chain is covering the worst of the chainring and shouldn't come off too easily anyway.

Image00019.jpg
there's about twelve feet of chain in total....


The mid-drive is a standard AW hub, salvaged from an old wheel.

Image00017.jpg
mid drive madness....


The output sprocket is a 24T one from a cheapo shimano freewheel (the one where each sprocket supports its neighbour in turn). I had to build up the ID of the sprocket with weld metal until it was a snug fit on the ball ring OD (which can vary from one hub to another BTW), then I ground six slots in it for the mounting bolts. This way I avoided having to drill through the sprocket where it might be hard. The sprocket is bolted through the RH flange using six M3 capheads, 12.9 rated, with nylocs and washers. I tapped each hole in the flange M3, but the thread wasn't strong enough to do much good. I guess it is slightly better this way (tapped rather than clearance drilled) if I ever want to use the hub in an ordinary wheel again. The sprocket isn't ideal because it has HG teeth on it, but it has worked OK so far. Obviously it is turned to face left so that it can drive rather than be driven.

The dropouts that hold the mid-drive bolt in with three M6 bolts each side, so can be respaced (for other IGHs) or replaced with a derailleur set if needs be. You will be amused to hear that the support crade is made from genuine gas pipe... and is designed so that it will accommodate input/output sprockets up to about 26T before there is a clash. I think I can go larger than that for a derailleur input sprocket.

Surprisingly the mid drive and the chains have yet to make me dirty, or get in the way when the machine is stopped. If I ever choose to put a fairing on the machine, the mid-drive is in the lee of the pedal circle, so there is no aero penalty. If needs be in the future I can fit a singlespeed rear wheel in a narrow fairing, and just use a derailleur mid-drive.

The fabrication was all done using MIG welding, and where necessary there was a fair amount of die grinding to get rid of start/weld toe defects and give more cosmetically pleasing weld beads. By some miracle the boom is actually straight, despite the potential for winding up being cocked sideways. The dangling seat tube I have left as a mounting point to allow future experimentation with 'retractable undercarriage'.

Parts of three rather horrid mountain bike frames and several sets of steel handlebars, plus the gas pipe were used to make the main frame. If you look you can see where it still says 'CODE' (from a Minerva code) and 'Hawk' (from a Hawk woodland). Quality stuff, eh... :roll: obviously the machine is no lightweight overall but it isn't too heavy either.

Fat tyres and/or suspension seem like a good idea BTW... potholes are presently torment, for both rider and bike.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Geoff.D
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Re: DIY recumbent bike....?

Postby Geoff.D » 1 Jun 2015, 3:56pm

"Chapeau", indeed.
I like the experimentation. The "suck it and see" philosophy works for me.

I like the hub brake, as a counter rim wear and inconsistency in weather conditions.
I like the high position, for its (I gather) increased stability at low speeds
I like the lack of heel strike
I like the intermediate hub gear, and the possibility of a further hub gear at the rear

Have you considered a straight riser from the steering head? I converted mine to this arrangement, topped it with a stem of an appropriate length (i.e. one I had in a back drawer!!) and fitted north road bars. My knees rise into the bend in the bars. This arrangement avoids any tiller effect, and allows me to mount lights. Judging from your photo, though, it's possible that for the bars to give enough clearance for your knees they might interfere with your eye line.

I'm not so convinced about the saddle arrangement, though. Perhaps the greatest positive, for me, about recumbent riding is the avoidance of a saddle between my legs! I can recognise that one gets used to new techniques, with practice. So, I wouldn't worry about having to dangle my legs in anticipation of stopping. But, I'm not convinced from the photo that a day's outing would do my bum much good. But, there again, you're sat on it at a different angle, with some weight taken on your back, so it might be OK. I hope this sounds like an observation (intended), rather than a negative comment (unintended).

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[XAP]Bob
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Re: DIY recumbent bike....?

Postby [XAP]Bob » 1 Jun 2015, 3:57pm

I imagine you get a significant amount of boom flex as you pedal as well ;)
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.

Brucey
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Re: DIY recumbent bike....?

Postby Brucey » 1 Jun 2015, 4:08pm

mercalia wrote:I wouldnt like being that high off the ground on my back incase of a fall - a long way to fall and do your back in? there must be a reason that bents are low?


Having fallen off a few times already at low speed, I think it is less risky in some respects vs a standard bike, if you are going to fall off. The reason is that by the time you know you are going down sideways, your whole body is already below saddle height, so there is less far to fall, if you like, and your head is far less likely to whiplash into the ground. I've not even grazed myself as yet, touch wood. I think that kind of fall is about as dangerous as falling out of bed, probably! It does take some getting used to though, you'd never sell one of these on the back of a quick test ride!

The height is an issue mainly because of the starting/stopping thing. I've built this machine absolutely as high as I can do whilst being able to get both feet on the ground and it isn't easy to do that, either, as I need to pull back on the bars and have my torso upright as I do so. As I mentioned earlier the saddle is a problem; I couldn't use the same kind of saddle as most other recumbents have, so there is a bit of work to do there yet.

A chum of mine has just bought a Bacchetta Corsa with 700C wheels (and a slightly lower saddle) so it'll be interesting to compare and contrast. So far I know one big difference; mine was about £2K cheaper... :wink:

cheers
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Brucey
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Re: DIY recumbent bike....?

Postby Brucey » 1 Jun 2015, 4:17pm

Geoff.D wrote: . ...Judging from your photo, though, it's possible that for the bars to give enough clearance for your knees they might interfere with your eye line.....


yup, I'm looking through the loops in the control cables, because I've got a high BB position. If I had bars 'over' my legs I'd have big viewing problems. I also have an idea that outstretched arms might be fatiguing too, but I guess it might be something you just get used to. Part off the reason for this riding position is that it is similar to that which will have to be used in a later fully faired machine.

The conventional saddle doesn't do that much; it is mainly there as a reference point, and to help me not slide sideways too much when starting off. The whole saddle needs a major sort-out; what I have there at present was just to try the thing out for size, I didn't expect to be able to ride it as far as I have done, even. It has not been without penalty though; I have removed the skin from my nether regions, which is just as painful as it sounds.

[XAP]Bob wrote:I imagine you get a significant amount of boom flex as you pedal as well ;)


Not much so far; I spin quite well and I think I'm putting as much effort in to staying on the thing as I am going forwards! The tubing is about 1-3/4" OD 1.6mm wall, so it is pretty stiff. The main frame is complete overkill, because it has two tubes that size in it!

cheers
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mig
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Re: DIY recumbent bike....?

Postby mig » 1 Jun 2015, 4:44pm

how does it fair on uphills brucey?

Brucey
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Re: DIY recumbent bike....?

Postby Brucey » 1 Jun 2015, 4:50pm

mig wrote:how does it fair on uphills brucey?


thus far, 'badly'.

I've got neither the right gears nor the right technique yet!

So far I've managed about an 8 or 9% grade but conked out on a steeper slope, mainly because of a very tight turn, I thought, but who knows...? It is all very different to what I'm used to.

cheers
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Cunobelin
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Re: DIY recumbent bike....?

Postby Cunobelin » 1 Jun 2015, 7:12pm

This may sound silly....


Don't get me wrong, I love the Kettwiesel, and all my other recumbents, but the polished, refined products today miss out on some of the pioneering and innovative aspects of my original recumbents of 30 years ago

Seeing machines like this reminds me of that era

Brucey
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Re: DIY recumbent bike....?

Postby Brucey » 1 Jun 2015, 8:16pm

I kept looking at other machines and thinking

'I wouldn't have done it like that'

and/or

'I wonder what would happen if I tried that?'

Where the diamond frame is an example of fairly convergent evolution for upright bikes, when you look at recumbent machines, there is little similar convergence, and things change enormously with relatively small changes in intended application or designer's whim.

The first ride was 'interesting' to say the least; I had got the machine to the point of rideability ( I thought) at 11pm on Saturday night, with the faint prospect of possibly racing it on sunday. So, tired and dirty though I was, I had to try it out.

After about four attempts, I managed to get started down a tiny slope at the end of my drive, and wobbled off down the road. I was weaving furiously, like I'd never ridden a bike before, ever. Visions of clattering one of my neighbour's parked cars ran through my mind with an unusually vivid clarity.

After a fair amount of wobbling and weaving I somehow got as far as a dead right turn and inexplicably made it round without coming to grief. A few hundred yards later there was a road which might have had traffic on it so I thought I'd better stop. I had no clear idea how to do this, so almost inevitably I slowed so far and then -somewhat gracelessly- I just toppled over. The ridiculousness of my situation was not lost on me; I was laughing like an idiot as I hit the road. I got up and tried to start off again, and realised that there was no slight downslope, and that I had no clear idea how to start off without it.

Thus my test ride ended with me walking half a mile home, wondering if I'd built a machine that I could ever actually ride properly.

The thing is, if I do all the other things I have planned, this machine will look vaguely normal by comparison with those....

cheers
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[XAP]Bob
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Re: DIY recumbent bike....?

Postby [XAP]Bob » 1 Jun 2015, 8:19pm

The act of learning to ride all over again....
Just don't do what Destin did:
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.