Thinking of DIY 20/20 SWB

Recumbents and all feet forward machines

Thinking of DIY 20/20 SWB

Postby Low Racer » Sun Oct 04, 2009 7:28 pm

I am comtemplating doing a diy project on a 20/20 SWB. Hopefully the end result would look a bit similar to the Azub Eco. The main tube would be an aluminium fence post similar to Pic 2. The 1 5/8" might be sufficient. I have seen them at Bunning and they in come two colorbond colours.

Fabricating a plate connecting the rear fork to the main tube. This will be held together with four screws and can be taken apart for easy packing if travelling. I am a total novice and have the faintest idea on welding. My neighbour is a welder and will be asking for his help if I decided that it's worth doing.

Where can I source the 1 1/8" head tube and at what angle should it be? Can you bond steel to aluminium?

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by BNA » Sun Oct 04, 2009 9:38 pm

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Re: Thinking of DIY 20/20 SWB

Postby John Lewis » Sun Oct 04, 2009 9:38 pm

Sounds interesting. You might do better in all steel. The reason I say this is because in aluminium you will need special grades eg 6061 T6. The welds will need TIG or MIG welding with the correct gas and welder type. Finally when it is done it will need specialist heat treatment. The aluminium is evenly heated to a certain temperature, soaked at that temp for a specific time and then dropped into a cooling bath which I think is ethylene glycol. I've no idea where you would get it done.

On the other hand steel is pretty forgiving. I use muffler tube and square section mild steel tube. It does mean it's heavier. If you have the ability or someone to do it for you then CroMo would save a little weight. You can either arc weld or braze. I've done both. My Bentech and TE clones are brazed and the other ones (Using the square tube) are arc welded. If I remember right the Bentech with its 26" rear and 20" front, disk brakes and heavy cheap components came in at ~15 kg.

Hope this is of some help.

John
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Re: Thinking of DIY 20/20 SWB

Postby }SkOrPn--7 » Sun Oct 04, 2009 9:40 pm

Hi Low Racer before you start buying things and committing to this project you need to get a few things in order first. I'm not sure how much you have researched this and I'm not sure of the full details of your neighbours ability so in order to further help we need some more info. First off welding Alloy needs special gear and can your neighbour do this or has the gear? Second point when talking alloy is the understanding of alloy strengths and what there used for so in saying that I doubt the Bunnings fence post would even come close to being suitable for the project at hand as your wanting an alloy frame. What your after is alloy in the 6XXX range which are relatively strong and have good corrosion resistance. Also some head tubes are made from 7XXX series alloy so if using 6XXX series welding becomes a problem due to the different alloy make up. Next is the wall thickness which needs to be determined to make sure it's load bearing ability can carry you and your gear and in my opinion alloy square tube is going to fail unless you undertake a design or a design that will better cater for the riggers of bicycle use using alloy so round tube or butted tube when dealing with alloy is a better choice due to strength.

Next if using a colour bond fence post the colour will need to be stripped of so no foreign material will enter the weld pool causing a week weld joint so keep that in mind it's best to start your project with raw material.

Some links to frame building supplies.

http://www.framebuilding.com/

http://www.cycle-frames.com/bicycle-frame-tubing/

http://www.fairing.com/default.asp

Head tube angle is another issue and where do you start in order to make the correct decision. I'm no expert but having done my own research I worked backwards and what I mean by that is I selected the forks I was going to be using and got the technical data on there strengths and work load which in turn gave me my starting point to determine the head tube angle I would be choosing and through all my own measurements and calculations it was 72 degrees. I also had a plan made up of the frame including the swing arm and seat which all adds to this complicated process of DIY builders and some of these things are unknown factors because you don't have the goods in front of you to play with and find there correct positioning so a little leeway is needed to do final tweaking. Using steel a greater margin for error can be used or changes made without the large worry of something failing but with alloy this is a different kettle of fish.

I know I'm making things sound complicated where as there not as bad as they sound providing you have an understanding and you have done research because working in alloy can be and expensive mistake if undertaken and something you do fails. That is why I'm being extremely cautious in listing the pitfalls you need to work out and understand first where as working with metal frames you can be a little more forgiving to the DIY builder.

Can you bond steel to aluminium? For the hobbyist or DIY builder the short answer is "NO" now having said that the answer is yes..........

I hope this helps a little.

Ricky
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Re: Thinking of DIY 20/20 SWB

Postby just4tehhalibut » Mon Oct 05, 2009 1:37 am

Not to detract from your enthusiam but the model that you are thinking of cloning is one that I don't like, the chainline on that bike is terrible. I've also seen similar on some of the Taiwanese bikes that you can get off Ebay. Look at how close the chain is when crossing the chainstay. You will either be forced to use an idler just to keep the chain up, or in the case of the Eco a black plastic tube, not so elegant.
The Bacchetta and RANS SWBs for example actually avoid the chain crossing over the top of the chainstay and do this by using special dropouts for the rear stays that put the axle below, not directly in line with the chainstay. I think that Trisled in VIC sell laser-cut dropouts like this. The beauty is that you also don't have to stuff around with an angled headtube in the frame, simply a 90 degree offset and then factor in the positioning and depth of the headtube and the depth of the rear dropouts towards getting the 'rake' that you want for your forks. This is elegant. You will need an idler (or black tube) somewhere on the frame but more for chainslap or keeping black oil stains off your calf than forcing the chain around the frame.
If you are re-using the rear triangle off a diamond frame or the rear suspension fork off an MTB then you will hit this problem with chainline that adapting the forks to a recumbent will bring. The other issue with the Eco was that it is a monotube design and a bit flimsy looking. The Bacchettas have this sorted, their main tube is not round, actually somewhat teardrop-shaped. The RANS SWBs instead used to be a round tube with a small triangle for the rear stays but now resembles the Bacchetta bikes, they have stayed with the round main tube but reinforced the rear forks where they attach to the frame, no longer needing any supporting tubing or triangulation. The issue is torsional rigidity (as well as not having the rear stays ripping out when you're riding to work). So look to how your forks will attach and how the main tube will flex under power and rider.
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Re: Thinking of DIY 20/20 SWB

Postby Low Racer » Mon Oct 05, 2009 8:31 am

Thank you all for the good responses. The idea started with googling DIY recumbent bikes. Some of these bikes are down right rudimentary and yet rideable. Whether it's safe to ride is another question.

Image

I agree that the Eco is flawed with the chain line travelling so close to the rear stay. It was discussed on BROL. However, someone pointed out that the chain does clear the rear stay when you are pedaling.

Obviously there's a lot more to consider than just weld this and that together. I have to do a lot more thinking.
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Re: Thinking of DIY 20/20 SWB

Postby }SkOrPn--7 » Mon Oct 05, 2009 9:41 am

Low Racer I would follow Johns advice and stick with steel as your main part of the frame and just4tehhalibut has brought up some very valid points and point that I also took into consideration then worked around in my own build. Don't be put of by all this still continue if you feel that you wish to do a DIY bent it took me 12 months to get to the point I'm at and asking questions here then looking at all the poor designs and quality designs ruling out the things I will not be doing and things to avoid. I had a clear mind to the direction I was going and that included a straight chain line along with no ugly teflon tube and a chain that travels under the stay and a frame that can carry a good safe work load well beyond those on the retail market. For a simplistic build I would stick with a Bacchetta type of frame build using steel I reckon they have it right by looking at the frame and you only have to listen to those who really have that bike too how good it is. :D

Cheers Ricky
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Re: Thinking of DIY 20/20 SWB

Postby John Lewis » Tue Oct 06, 2009 11:50 pm

Lowracer,

This might be a good starting point. Designing a great handling bent.

http://bikesmithdesign.com/Design/12Steps.html

Also have a look at the AZ Highroller for ideas. It can build as 26/26 20/20 or 26/20 with minor variations.

http://www.atomiczombie.com/product-highroller.htm

You might find some ideas here too.

http://www.fleettrikes.com/

Hope you have a go. I started by following a design pretty much exactly. I didn't expect much and surprised myself. Once you have one under your belt, no matter how it turns out, You will be better placed to build that dream machine.

John Lewis

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Re: Thinking of DIY 20/20 SWB

Postby Doorknob » Thu Oct 08, 2009 9:23 am

Don't forget to research brazing to assemble your bike. Hot glue for metal.
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Re: Thinking of DIY 20/20 SWB

Postby Low Racer » Thu Oct 08, 2009 5:41 pm

John Lewis wrote:Hope you have a go. I started by following a design pretty much exactly. I didn't expect much and surprised myself. Once you have one under your belt, no matter how it turns out, You will be better placed to build that dream machine.

John Lewis


Thanks for the linkies and encouragement, John. I am sure you are right that once I had one under my belt, I'll be more confident doing a second one. Lots of reading first though.
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Got myself a Bird

Postby Low Racer » Mon Oct 26, 2009 5:13 pm

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Got myself a Birdy as my commuter bike. Not gonna try building as it is beyond my capability.
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Re: Thinking of DIY 20/20 SWB

Postby Uba Tracker » Mon Oct 26, 2009 7:41 pm

Hi Low Racer, as much as I like the Birdy I must say I was disappointed to find that you abandoned the prospect of building your own 'Bent. All of the advice offered was spot on the money but it's alot of advice to absorb and in reality you needn't try to understand all of of it immediately. Learning is a curve (I'm sure I don't need to labor that point to you) and how steep you make it is up to you, you might very well take ten years to build your 'Bent, but so what, at the end of it you have undertaken a great journey of self discovery and satisfaction. I'm almost certain that John, Ricky, Just4tehhalibut and all other home builders would agree. I hope you reconsider.

cheers

Harry
A bad day's riding beats a good day's work everytime
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Re: Thinking of DIY 20/20 SWB

Postby Low Racer » Mon Oct 26, 2009 9:59 pm

Uba Tracker wrote:Hi Low Racer, as much as I like the Birdy I must say I was disappointed to find that you abandoned the prospect of building your own 'Bent. All of the advice offered was spot on the money but it's alot of advice to absorb and in reality you needn't try to understand all of of it immediately. Learning is a curve (I'm sure I don't need to labor that point to you) and how steep you make it is up to you, you might very well take ten years to build your 'Bent, but so what, at the end of it you have undertaken a great journey of self discovery and satisfaction. I'm almost certain that John, Ricky, Just4tehhalibut and all other home builders would agree. I hope you reconsider.

cheers

Harry


Thanks Harry. Maybe one day I will. I am overwhelmed with info (BTW thanks guys for all great info). I couldn't pass with the good price for the Birdy and it folds to nice little package.
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Re: Thinking of DIY 20/20 SWB

Postby }SkOrPn--7 » Mon Oct 26, 2009 10:52 pm

That's a cute little bike I have never heard or seen it before so hope all works out and the bike services your needs. Harry has hit the nail on the head while you have purchased the Birdy for now this will give you the breathing space to now take a leisurely approach to doing your research and understanding the DIY world of bike building and with any luck continue with your own project. :D
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Re: Thinking of DIY 20/20 SWB

Postby jaffaman » Tue Oct 27, 2009 9:26 pm

Low racer, I have some folders as well, and must say one thing that is worth doing is really experimenting with the setup. As shown in the picture it is setup like a road bike - seat up a little higher than handle bars. One of the nice things about the folders is you can really muck around with this - I have found my favourite position is more upright, so I have lowered my seat, pushed the seat back as far as it goes, and raised the handlebars, and also experimented with different length stems to move the handlebars forward and back. Of course, this is fine for cruising around, but if I want to push it a bit harder I can quickly reset it to the sort of position shown with the seat up and handlebars down. I guess the point is that your bike allows a lot of adjustments, so play with it a bit and find what you like and what you don't.

One day (maybe soon) one of the folders is going to be reinvented to a swb folding semi recumbent I think - either with a cruzbike conversion http://www.cruzbike.com/conversions, or something more radical. If you still like the idea of a recumbent, I reckon your birdy may make the journey to cruzbike OK - seems to me to have the right configuration for this to work, though the birdy's rather unique front suspension may get in the way? If it worked it would get you real close to what you had in mind in the first place.
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Re: Thinking of DIY 20/20 SWB

Postby John Lewis » Tue Oct 27, 2009 10:26 pm

Hi Lowracer,

Nice little folder. Reckon it would make a neat SWB. :D

Seriously though There is one made from a Dahon (I think) folder. It has a Cruzbike seat and the boom has been clamped in position. Think it was a pro job. It was for sale some time back. There are some photos on the WAHPV Yahoo group site. I think in the first photo folder if I recall. You will probably have to join the group to look.

John Lewis
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Re: Flicked Birdy for a Cafe

Postby Low Racer » Sun Feb 07, 2010 7:39 pm

In the process of getting the Birdy to the new owner. Good though as it is, I still like the recumbent. Can't resist putting the winning bid for Bacchetta Cafe when it appeared on evilbay last week. The seller just delivered the bike this arvo. The bike is very heavy compare to the Birdy. Took me, maybe 20 seconds, to get use to the Cafe (compare to the M5). Once I accustomed myself, it's a blast to ride. I will be enjoying my commute to work even more.

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Re: Thinking of DIY 20/20 SWB

Postby just4tehhalibut » Wed Feb 10, 2010 3:12 am

Lucky you, they don't sell that rear rack anymore and that bike, sweet as it is, doesn't take someone my height.
I have the Giro20 and use this to commute 25km into work, I've set it up with a seat bag for most things, a FastBack Norback frame bag for pump and tools and a underseat rack for the occasional pannier use. I like the weight midships rather than up high or behind the seat. http://www.terracycle.com/Merchant2/mer ... ory_Code=R .Ian at Flying Furniture might have the rack, remember to specify Cafe model where or when you find one. I either use the small Ortlieb panniers or the very large shopping pannier.

This is what the setup looks like http://www.bv.com.au/great-rides/42315/?photo=636
Yes, there is a bit of frontal area but the handling was better and it doesn't slow me down much. A few other commuting modifications were that I used a frame bag on the front for the rechargeable battery, got tired of unstrapping it to take it in for a charge up, also I machined up a bracket for a kickstand as I didn't like the stands that Bacchetta sells, the local generic stand (under 'Giant' ?) was better. You'll find other tweaks, enjoy.

P.S Check the serial number on your frame and the Bacchetta inspection notice http://www.bacchettabikes.com/support/tech_update2.htm
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