News and Events

Keep up to date with the latest news and events of Modular Bikes.

Friday, October 22, 2021

Fixing 50 bikes, 35, Oxford with Shimano Positron

 

As traded, by this stage I had removed the completely stuffed gearchanger and twin cables, and got the bike working in high gear.

Positron gearchanger.


Hi

A while ago, I fixed and documented working on a Malvern Star bike with a Positron II groupset, and have now brought home from Wecycle an Oxford International bike with a twin cable rear derailleur Positron. Anyway, this shows a few pics. Will post more soon, but meanwhile here is a forum post about another bike with a similar (ok, crap) setup, and another one, and another one. The Disraeli Gears site has a full service manual I can access, that's good!

Update, 24 October 2021

Spent much of today working in the bike. As the photo of the gearchanger shows, the change has 2 cables going to the rear derailleur, one pulls it left for low gears, the other pulls it right for high gears. From the link above to the manual, I found that cable assemblies (Shimano 6060010) are still available, and that would repair the bike simply with its original changer. And its likely that with a tandem gearcable, and 2 new cable outers, the same fix could be made, with maybe a small abount of finneagling. Another possible mod would be to drill or file out the changer so 2 cables would fit under the  pinning screw.

Anyway I did none of these, see photos below:

3

4

5

6

7. Steel Plate on stand bracket,

8

9

10

11

1. Took off and cleaned the stand, and made a small steel plate which is bolted onto the top of the stand bracket. It has an m6 bolt coming out of it. (Photo 7)

2. Ran a cable outer from the left derailleur cable position to the boss on the chainstay, then ran an inner cable and spring up to the bolt in the stand. After a bit of checking and spring swalling, I had the spring doing its job, moving the derailleur to the right. (Photos 4 and 9)

3. Mounted up a 5 speed gearchanger on the stem and ran a cable to the right derailleur position (4). A bit of fiddling later and all 5 gears are rechable.

4. Went for a test ride and it works well. Found a rack on hard rubbish and I will probably fit it to the bike soon.

Regards

Steve Nurse


Fixing 50 bikes, 34, Fiorelli 27" to 700c conversion

As traded. The back brake was originally missing and I put on in place for this photo. A genuine bitsa as I found it, with a steel crank on one side, aluminium the other, a steel 700c alu front wheel and 27" steel back.

Close up.

Derailleur swap, long cage (on bike) replaced short cage tourney.

Fixed up. This was taken on the night Melbourne's lockdown 6 was finally over. Test ride was to get the beers shown in the pic at our very local brewpub . And I cooked dinner on a barbecue, the full extent of post lockdown celebrations.

Hi

This bike was left abandoned on the east end of our street where I've found and taken in one or two others. As traded it was a bitsa with a mix of steel and aluminium parts and 2 different wheel sizes. The front wheel was the current very popular 700c size, and I had a spare 700c back wheel and tyre, so I decided to go with all 700c alu wheels for the fixed up version. That meant bending the back forks apart, and I managed this fine by hand. The frame's relatively weak compared to the 20" front forks I sometimes bend.

Along with the alu back wheel, I added a long cage derailleur, and a 52 / 40 alu right crank. The front wheel ended up being out of true. I had fixed this a bit before abandoning it - Suzie gave me a few 700c wheels and I ended up using one of them. For the first few times I pumped up the front tire, it didn't stay on, and then came the fitting of brakes and gearchange tuning. The chain rubs against the frame on the 11t gear and I've fixed that just by tuning the gears so it only gets to the 2nd highest 12t gear when changing up. That is heaps high enough.

So the bike went well on the test ride to a pub for takeaway beers at the end of one of our lockdowns. I like the way it looks, sort of retro-cyclocross. I'm not sure this would be a Wecycle customer (refugee) bike, but it could easily sell for $100 or so.

Regards

Steve Nurse
 

Monday, October 18, 2021

Rear suspension bike summary

 



 



 


 


 

 For several months, I’ve been making and trialling a new recumbent bike. Its unique feature is a rear fork suspension with rubber blocks. The blocks rest inside the rectangular frame and compress over bumps. This is a new concept, but the rest of the bike – seat, tailbox, front end - is based on front wheel drive leaning trikes I have been riding for years. As with all my cycles, aims with this bike were to be aerodynamic, light and have good load capacity.

The rear fork has no pivot point and finds its own position. The fork stem is from brazed steel tubes stacked as a rectangle.  With 3d printed plastic spacers each side, a pin to hold position, and the rider’s weight, the fork can only rotate in one plane and acts as suspension. The suspension blocks are cut down portions of Mckay industrial dampers. Although other rubber material can be used (pedal rubbers, cycle tyres and tubes), the industrial dampers are designed for suspension of this type, so are stable over a wide range of temperatures.

It’s taken a long time to come to this design as I started building front wheel drive bikes with the rectangular hollow frame that could use it in about 2012. Here is a blog post from back then.

The 2012 bikes and some of the trikes I’ve built since have used Capral rectangular hollow 82.6 x 28.6 x 2.3 wall aluminium beams with a combined tailbox and seat. The tailbox is aerodynamic and has about 50 litres of storage. It clamps to the beam and slides up and down the beam to adjust for leg length. It’s removable and doesn’t need any frame holes or bosses for support or grip. The trick to using this aluminium section is that with the front wheel drive I use, there’s no frame chain stress, so stress is mainly from body weight. This means a relatively deep and thin section of tube can take the stresses and not flex too much.

Bike rear triangle circa 2012

 
2012 bike on Murray tour

The first frames of this type were fabricated by Michael Rogan from  MR Components in Hastings, and they included reinforcements and pivot bosses at the back. But since then, I’ve worked out how to do leaning trike frames at home with some custom cast parts, some 3d printing, handsaws and a drill press.  A plan for the leaning trike is on thingiverse at https://www.thingiverse.com/thing:4201871 . This latest rear fork borrows from the design of the front frame join: body weight under gravity helps keep parts together.

So far the new bike works well and I’m happy with it. For me it takes more shed time to produce than the equivalent leaning trike, but the bike back end weighs less and should have less rolling resistance. A nice modularity is also possible, with the same tailbox and front section accepting a bike or leaning trike rear end. The rear wheel and fork detaches quickly from the bike by removing one screw, then some jiggling. That should be good for fitting the bike in trains or cars.

The bike’s tailbox is still a work in progress, but I am confident I will end up with a light design. At the start my shoulders were too far back, and I’ve made  a temporary wedge that pushes my shoulders forwards but is also a small glovebox for keys, wallet, phone, camera etc.


 

Here are the parts for the back of the new bike and the equivalent parts for a leaning trike.


 

Bike back frame & wheel

Parts: 2 Custom rubber buffers, 1 custom fabricated fork, 4 3d printed guide plates, screws, custom wheel build includes dynamo (4 sets of parts)

Frame drilled one place only

Rear frame & parts weight: 4.6kg

 


 

Trike back frame and wheels

Parts: Unicycle cranks, YST bottom bracket, 2 custom bearing housings, 2 custom wheel axles, 2 standard pedal prix trike wheels from MR components. (5 sets of  parts)

Frame drilled 4 places.

Rear frame & parts weight: 5.2kg


 

 Forces and movement of back wheel

With 2 separate elastomers working at the same, the rear wheel dynamics aren't immediately obvious.  But each elastomer can be considered a pivot point  as well as compliant suspension, and when this is done some motion / suspension equations can be worked out. In the diagrams above, the top line is the resultant of the two lower motions. The simple version has equal spring rates and distances, and the general version has unequal distances and spring rates.

 

 

Regards

Steve Nurse

 

 

Friday, October 15, 2021

New Bike Part 12, a ride with Bryan Taaffe


 








Hi

Yesterday I did a bit of work on my bike. I wasn't happy with the ergonomics and felt I was leaning back too far, so added a plywood and timber wedge to the seat so I'm a bit further forward. It looks a bit crude at the moment, but having done this much I think I can make something decent. It will probably mean redoing all the corflute, but in the end it should look good with corflute covering both the new front and old back sections of the tailbox.

Meanwhile I have been in touch with Bryan Taaffe, an Irish cyclist and metal fabricator who has broken the record for an unsupported crossing from Perth to Sydney. We met up on the Kew Boulevarde and did 2 laps, about 25 k together. He's a bit faster than me downhills, but much faster uphills. Ok, he slaughters me and just about every other bike rider on the training route. But my bike (homemade front wheel drive) still goes ok compared to his (imported M5 Highraccer). 

Bryan's rig didn't have much storage space, maybe 20 litres, but that was enough for the Perth to Sydney trip, he managed things very well.

It was very good to finally meet Bryan after I'd interviewed him by phone for the OzHPV Huff magazine. We naturally talked recumbent bikes, and chatted to a lady who was interested in our recumbents and Bryan's work for the Alive charity. Will no doubt catch up with Bryan again soon.

Tuesday, October 12, 2021

Fixing 50 bikes, 33, Suzies Graduate

Cyclops Graduate

Drilled a hole through the stand retaining plate so the gear cable went through neatly

This is a before photo! This gizmo was securing the rear rack, not that well.

The right bearing cap was hard to remove and I worked this out, by tightening a large bolt onto the cap, and then keeping on turning, the cap eventually comes out.

Here is the whole assembly, I put an aluminium tube in it so the bearing surface wouldn't be damaged. I replaced this bearing cap with one with some flats on it.

 

Hi

This bike was dropped off by our friend Suzie, and the pedals had cotter pins, and the bearing cage had disintegrated inside the bottom bracket, so she wasn't a very happy bike. So quite good progress today, gears and bottom bracket are restored, tomorrow I will do a switcheroo on the rack and should be able to finish it off.

Monday, October 11, 2021

New Bike part 11, the bike that named itself.

Trial (top) and final tail box back.

went into this! Small plywood piece is tailbox latch.

Inside. Need to trim a few cable ties still.

Done

and done.

 
Top lid design. Diagonal lines are 20mm apart and together make the 90 degree bends in the part.

Bottom part. Not quite how I made it, but how I would make it next time.


Hi

Today I completed most of my recumbent bike. This involved finishing off the tailbox by making and then attaching the back piece, as well as making a boot catch. I'd already had a go at this by tracing the required shape on corflute, the cutting out.

But this wasn't that great, so I started over again this morning and made another piece, mostly from the plans of the top and bottom pieces, but also from direct measurement of what had been built. This time it went better, and between using cable ties, sticky tape, and a soldering iron finished off the box quite well.

Went for a ride, and it works well. The brakes pull the bike up very sharp if you apply force.

As far as the name goes, its "Properly Satisfying" which matches what is written on it. This is from the tailbox lid material: corflute advertising material for a type of pie.  Considering the amount of effort put in, and that it goes quite well, the name fits. Well better than "Tasmania's National Pie since 1942" anyway.

It was entirely up to me to mount the top corflute sign-side-out, and I think it adds to the bike. Anyway I'm happy with it.

Next Post

Saturday, October 9, 2021

Fixing 50 bikes, 31 and 32, Giant Cypress

Miley and Billy Ray as traded

 Hi

 Today I was visiting my Mum and Dad, and on the way home stopped at a free book depot, and then continuing on the same long street spied the bikes shown above. At first I thought it too good to be true, but then on going back to check, it wasn't, there were 2 bikes there free to good home. They are Giant Cypresses, one step through and one diamond frame.

Anyway, after a minor struggle getting them into the car (couldn't close the back hatch, so I secured it with a mancky bit of string ) drove home carefully.

Not too much wrong with them, and I have already taken the chains off and they are soaking in vinegar to derust. One of the big problems seems to be the gearcables on the diamond frame. The coatings have disappeared and they're now just a mess of rusty wires.

After thinking a bit, I decided to call these bikes Miley (step through) and Billy Ray (Diamond frame). Of course I then thought of Miley Cyclist and Billy Ray Cyclist. Ok, Dad jokes over.

Update October10


 The Cypress bikes really couldn't be stored under cover at our place, and I was relieved to hear that Simon from Wecycle had room at his place for 2 I'd fixed. He's about a kilometre away, and I rode one bike (steer / brake / gears right hand) while pushing and steering the other (left hand) to his place and deposited them in his back yard. 

Then I walked home, and found the Mongoose bike above (or ex-bike) in a pile of rubbish outside a building site. I grabbed the bike, and 2 people asked me on the way home if my wheels had been stolen!

In the afternoon, I worked on the step through Cypress out the front of our place on a very pleasant afternoon, and got it going, swapping over rusty handlebars and a gear cable outer from the Mongoose.  The Mongooses rack didn't fit the Cypress, it was too small. Little bit of cleaning up still to do, not much. 

The test ride of the step through Cypress was amusing. It rides well and has a very upright ride position, and the spongy seat was full of water from being left outside. So I got wet shorts, and it looked like I'd p#$%ed myself, and I showed off this fashionable effect to my wife Christine who was reading on the verandah. "I just couldn't wait" "Couldn't hold it back" We are in the midst of a very long lockdown, you do need to laugh about something.

The step through Miley all fixed with reflectors and rear rack added. Should be a nice bike for someone. Rack is from Suzies bike which now has the Mongoose rack.
Here is Billy Ray, mostly fixed. All the gearcables were changed, and the left gearchanger / brake lever was swapped too, it only selected 2 of 3 gears.

Billy Ray, ready to go. Its a big bike, with a 54cm seat tube plus the extra height of a suspension seatpost. Drink bottle cage from Mongoose.

New rack on Mylie, carrying a 27" wheel,

as delivered to Wecycle. I made out a tag for her at this stage, so she can be selected and go to a new home.