Author Topic: Recumbent trike (hopefully folding)  (Read 16316 times)

Re: Recumbent trike (hopefully folding)
« Reply #50 on: September 19, 2017, 04:12:23 pm »
I figured out how to build a seat extender that allows an adjustable angle by using an old folding bike stem. So I cut the centre off an old set of handlebars and welded them onto the seat post. Sadly my welder was out of gas and the welds sucked, so I need to get some more gas before I can try again...

Re: Recumbent trike (hopefully folding)
« Reply #51 on: July 24, 2018, 03:52:08 pm »
Almost a year since I last updated this.  :-[
I need to get on with making it usable - my daughter is pestering me to ride it work before she goes back to school (though the chances of her being able to ride it are almost nil (it's set up for me at 6ft and she's 4ft - pulling the bottom bracket back far enough for her to reach would mean the cranks bashing the crossbeam)).

I did look at my little scratch start TIG, but the dials on the front are damaged/missing - I should probably just get rid (and, if funds allow, get something more modern).

Kim

  • Timelord
Re: Recumbent trike (hopefully folding)
« Reply #52 on: July 24, 2018, 06:57:27 pm »
I need to get on with making it usable - my daughter is pestering me to ride it work before she goes back to school (though the chances of her being able to ride it are almost nil (it's set up for me at 6ft and she's 4ft - pulling the bottom bracket back far enough for her to reach would mean the cranks bashing the crossbeam)).

Don't underestimate the ability of a sufficiently determined child to ride a recumbent that doesn't even slightly fit :)
There's a photo somewhere of EldestCub successfully riding my Streetmachine with his shoulders leaning on the bum-end of the seat and his back arched over the steerer...
Careful, Kim. Your sarcasm's showing...

Torslanda

  • Professional Gobshite
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Re: Recumbent trike (hopefully folding)
« Reply #53 on: July 25, 2018, 09:25:10 pm »
Many, many moons ago Redshift and I were standing on Morecambe Prom eyeing up various offerings at CycleFest. I suggested she had a go on a Trice and got a vaguely negative response which included 'It's probably set up for someone much taller!' and so on.

Five minutes or so later a chiddler of about 7 trundled past on one. Backside wasn't even touching the seat . . .
VELOMANCER

Well that's the more blunt way of putting it but as usual he's dead right.

Kim

  • Timelord
Re: Recumbent trike (hopefully folding)
« Reply #54 on: July 25, 2018, 09:33:33 pm »
Five minutes or so later a chiddler of about 7 trundled past on one. Backside wasn't even touching the seat . . .

I have grainy video of ?SmallestCub photobombing a BBC Midlands Today interview about all the cycle infrastructure they were about to build[1] by doing just that.


[1] Spoiler:  They didn't.
Careful, Kim. Your sarcasm's showing...

Re: Recumbent trike (hopefully folding)
« Reply #55 on: July 26, 2018, 09:42:48 am »
Many, many moons ago Redshift and I were standing on Morecambe Prom eyeing up various offerings at CycleFest.

The last of those glorious events was in 2004!  :o

If it ain't broke, fix it 'til it is...

Re: Recumbent trike (hopefully folding)
« Reply #56 on: December 29, 2019, 07:15:32 pm »
I molished a random backrest for this and rode it on the rollers today.
The old backrest was shaped ply with special captive nuts and sensible bolts, but I couldn't find it in the garage! New one was a part of a shelf, held in place with wood screws. Worked better as it had more height and so supported my upper back better! Now all I need to do is cut some random steel, bend it to a suitable headrest position and work out how to stiffen it sufficiently to stay there. :)

Side note - I saw on a BHPC picture the other day a steering damper on some old trike. Anyone know what that was nicked from? It might make it easier to ride this thing (outdoors) without every tiny bump bouncing the steering around the place.

Re: Recumbent trike (hopefully folding)
« Reply #57 on: January 19, 2020, 10:38:57 pm »
I resolved the neck rest with more wood, and I rode it about 5 times on the rollers. I've gone back to the upright for now as I can't get enough resistance on the rollers (I was in the biggest gear I have at 90rpm doing around 200W), and also because I don't have my 'bent legs and I don't want to lose fitness getting them (this is, after all, just an experiment - I'm not racing the thing).

I can answer my own question - there are loads of steering dampers for go carts and also for motorbikes on eBay.  At some point I'll actually try riding it outside again, and maybe at that point I'll decide it needs one, but I'm not going to bother until then...

Re: Recumbent trike (hopefully folding)
« Reply #58 on: April 08, 2020, 09:55:44 am »
It's back on the rollers (so that my head height and that of my daughter are roughly equal), still with the issue that I can't get enough speed on it to get proper power.  I have noticed that I seem to gravitate towards 75rpm rather than 88 or so on the upright. The cranks are 175mm long secondhand carbon ones that I found lying around in my garage, but they have the benefit of 30-40-50 rings and a new BB, so they are going to be staying for a while I suspect.  I'm also wondering if I can get my jackshaft to work again. Chain tension was the problem last time, but I reckon I can just run a regular short cage derailleur on the front loop of chain if I set it up properly. Experiments beckon on that front, because I have all the parts. :)
I also want to get a new seat, because the wooden one sucks. It will almost certainly end up coming from overseas, and cost more than any other part on the trike (even a fibreglass one), so I've not got much further than looking at them online. It would be a lot more convenient if I could actually try one!

Getting my daughter onto the turbo necessitated a little bodgery:
2020-04-03_06-25-30 by duncancmartin, on Flickr
Unfortunately, having moved the pivot so that it can contact the wheel, the bolt to hold it at the right tension is too short. For the moment, it's got a bit of wood propping it into the right place (this is definitely "bodge it") - at some point I am going to have to try to find a suitable long bolt. It works though. :)

If I can sort out the trike such that I'm happy riding it consistently, I might apply this bodge to my wheel on smart trainer and see what she thinks of Zwift! ;)

Re: Recumbent trike (hopefully folding)
« Reply #59 on: April 18, 2020, 04:07:08 pm »
I think the trike seat is actually bad for me when I'm trying to ride at a reasonable power. Fundamentally, the backrest is a shelf, so it's only about 6 inches wide, and I think that if I push back into the seat then I end up sort of flexing my back and pulling wher emy ribs join my sternum.  Combined with breathing a bit more, that hurts.

So, I have a new seat design.  I downloaded the plans from a user called Atom on the bentrider forum, and made the form, around which a seat can be produced. It ended up being re-inforced in a few places as just having these bits was a bit wobbly, but I don't have a good photo of that!
2020-04-18_03-57-36 by duncancmartin, on Flickr

Unfortunately, I couldn't find anywhere that would deliver the required 3mm plywood in these strange times, so I thought I'd have a go of making it out of 1.2mm zintec steel (I happen to have some of that lying around, plus some really handy tools for cutting it). And I can always weld it to stuff too. I was even wonder about panel beating those little wings that are supposed to hold you in place, thought I may end up just cutting it a bit and then welding them on. I made it 35mm wide, because I figured I could always trim it down - while welding extras on is fine, adding a few mm down the entire length is beyond my skills!
2020-04-18_03-57-56 by duncancmartin, on Flickr

Hopefully when I release my ratchet straps it doesn't just spring back! I'll probably lose a little bit of the shape, but that's not too big a deal - I can always use the ratchet strap to basically turn it into a circle and then straighten out the middle bit again. The only minor annoyance is that I've actually managed to strap it to the Workmate! This is probably good for the rigidity of the structure, but it doesn't help me get it into the garage! So it might just have to be released this evening.

Once I'm happy with the shape I need to work out how I'm going to attach it to the trike. Bracketry is fairly simple to make though, so hopefully that won't be a problem.  Maybe I can even make it adjustable? First things first - get it to a shape I can sit on!

Re: Recumbent trike (hopefully folding)
« Reply #60 on: April 18, 2020, 05:50:43 pm »
As expected, it sprung out a lot. :(
2020-04-18_05-48-24 by duncancmartin, on Flickr

So I took it off the buck and over-bent it. I'll revisit it tomorrow.
2020-04-18_05-48-41 by duncancmartin, on Flickr

Re: Recumbent trike (hopefully folding)
« Reply #61 on: April 18, 2020, 08:29:05 pm »
It just sprung back. And it's heavy. But it kinda works when I put it straight on top of the existing seat.

I have a piece the same length about 10cm wide. I could just whack that piece into my mould so it's basically the same shape, and then put them into the mould together to the right shape, before welding them together. Hopefully that would add a bunch of rigidity, in the same way that laminating the plywood does. It would add yet more weight, but it might make it work as a seat.

I saw someone on YouTube cutting 1mm deep lines into his plywood so he could bend it properly. I could do that if I had a cirular saw, but I don't have a suitable tool I don't think. :(

Re: Recumbent trike (hopefully folding)
« Reply #62 on: May 27, 2020, 02:03:19 pm »
I got some thin plywood when I was ordering other stuff to make a bench. My wife didn't appreciate me leaving a couple of "bits of wood" in the bath to soak, but I think this is a result:
Bending one sheet:
IMG_20200524_195626 by duncancmartin, on Flickr
Sticking the 2 together (count those clamps)
IMG_20200525_203449 by duncancmartin, on Flickr
I think there were 4 welding clamps and 9 G clamps of various types and sizes. Plus I added a bunch of staples (and then my staple gun ran out.
Result. :)
IMG_20200526_201234 by duncancmartin, on Flickr

There's a few voids around the edges, but it's 16 inches wide (and 4ft long) so it needs to be cut down anyway. I got that size because it meant that 6 pieces fitted onto a 8x4 sheet with nothing left over. I guess if I trimmed 3" from the side I could stick that on the back in the middle and really reinforce it. It's pretty sturdy though, so if I make a sensible bracket to go on the back I could probably attach it to my trike quite neatly. Sadly my hip is irritating me no matter what I do, so I'm not going to be riding it for a while. I might even hand onto the seat and see how it goes on my new 2 wheel recumbent. Watch this space for developments (I'm designing it myself so I need to teach myself fusion 360 before I start chopping steel up, otherwise it will all be wonky!).

Re: Recumbent trike (hopefully folding)
« Reply #63 on: June 07, 2020, 09:32:58 pm »
Good work. Work done is never wasted as it's all about the learning. The thing that leaps from the page for me [save the fact you've built a seat for yourself] is that you're moving imperceptibly onto making a composite version :) The lightest and stiffest way forward. Way to go.

Once you've got the shape right, as it looks as though you're very close to getting with that plywood seat, then you're well on the way to having a plug/mold to shape with. Working with composites is another learning curve, but it's well possible with the very minimum of equipment. It doesn't have to be carbon fibre either - glassfibre is perfectly adequate.

Getting back to the present though, your plywood seat will be plenty strong enough, but, depending on how you attach it to the frame, some unwanted flexibility might be an issue. But you'll have to see.

Watch this space for developments

We will be :-)
Garry Broad

Dave_C

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Re: Recumbent trike (hopefully folding)
« Reply #64 on: June 08, 2020, 12:14:37 am »
Great thread! Many thanks for bringing this back up.

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@DaveCrampton < wot a twit.
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Re: Recumbent trike (hopefully folding)
« Reply #65 on: July 17, 2020, 10:27:44 pm »
If you want to do a composite seat the ply form will work as a mould. The lazy way of doing this is with the ply  in vaseline to make it release. I did a lot of bodywork mods like this on my mother's Marlin kit car and they all worked very well. For a proto you don't bother too much about moulding finish as you can sort that out with sanding and polishing afterwards (even if the purists would say that this is work that should be done before producing the article rather than afterwards but for prototyping that doesn't make sense to me and my way is much quicker.