Experimenter

[Simon Rafferty]

I've built several electric bikes over the years. The only one on line is this:
http://www.evalbum.com/609
Though there are some pictures of one of my folding recumbents here - but kind of small!
http://www.sproklegrommet.co.uk/

More recently, I've been experimenting with a 3D Printed friction drive using a 63mm outrunner motor - which works surprisingly well! No machining required, just printing & a bit of soldering.

At the moment, I'm building a very small, light weight folding electric bike to wizz me around Pinewood Studios (the walking is killing my feet). It has to be fully road legal and comply with current EPACS regs - leading me to experiment with torque sensing. With some success!

 

[Cooper]

Oh, man, I am completely captured by the idea of 3D printing. I used to do 3D modeling back in the day and I keep promising myself I'll take time and refresh my skills.

I still don't understand how you 3D print metal components (I assume they're metal) that are structurally strong enough to do real work. How much of the 3D work are you doing yourself?

 

[Simon Rafferty]

All the parts are printed in plastic (PLA) so within the reach of any low cost printer.

Although some parts need to be strong, if you understand the nature of the material - it's not too hard to design something practical.

As an example - the material is strong in copression, but weak in tension - so you need to make tensile elements thicker than compressive ones.

Once I'm happier with it, I'll post it on Thingiverse and a link from here.

I have an Ultimaker 2 printer - and it gets used every couple of days. At work there are a variety but mainly Ultimakers as they are considered about the best of the hobby / business crossover printers. If you're interested, look for a used Ultimaker 1 or 2. They can often be had for a few hundred pounds. They are fully rebuildable with a full inventory of parts available. I bought my UM2 from eBay and replaced a couple of worn out bits turning it into a new printer in effect.

Si

 

[Cooper]

That's fascinating, Si. Thanks for taking the time to explain. I look forward to following your work.

I don't suppose there are videos of you riding that triangular thingie...? It looks decidedly like something the coyote would order from Acme.

 

[Simon Rafferty]

I don't suppose there are videos of you riding that triangular thingie...?

I don't I'm afraid - I built it quite a long time ago. I've never been very good at documenting stuff I've built as it's been a personal journey of discovery in the main - and there's always been something new and more interesting to move on to!

I tried changing the motor for one of the ones from an electric 'hoverboard' as you can pick up broken boards on eBay for peanuts. It didn't work terribly well mechanically - but it was just a quick Sunday Afternoon project. I'll have another go when the interest comes back. Power wise it was fine - but because the motor is only supported on one side, the single rear fork was flexing too much.

It looks decidedly like something the coyote would order from Acme.

Story of my life!

This is the current build in Solidworks. Laser cutting should arrive on Monday and most of the other bits have been delivered.


Folds to:


According to Solidworks, the all up weight should be 12kg which isn't too bad. It's mostly being cut in 2mm 304 Stainless so it looks Engineeringey!

It's powered by 3 x 3S Turnigy 5Ah 30C Batteries. It won't give a huge range (12 miles based on previous experimentation) - but honestly, would you want to travel much further on a bike like this?

I wanted something that will fit in the boot of my car and that I could stash under my bench at work when it's not in use.

This is the 3D printed Friction drive:

Which just uses two of the same batteries and gives about 8 miles assisted use.

Si

 

[trex]

you are a genius. Your friction drive is the best I've seen.

 

[anotherkiwi]

I can see you 3D printed your battery/controller holder, very nice! How large a piece can one print on a hobby printer? Thinking about my own lipo battery box not the exterior which I would do in ply as planned but an insert to hold the lipo bricks in place.

 

[Simon Rafferty]

My Ultimaker 2 will print objects up to 23 x 22.5 x 20.5 cm - though printers such as the Lulzbot Taz print a fair bit bigger and in the same quality.

One of my favorite uses for it is making cases for electronic projects that snap together like Injection Moulded enclosures and make said project look much less like it's been built by 'Fred in a Shed' (or even Simon in a Shed!).

The trick for anything bigger is to make it in bits that snap together. The battery & controller enclosure also has a middle bit which fully encloses the batteries. It's made in several parts - Top & Bottom caps, top & bottom battery spacers (with a cut-out in the back which surrounds the seat post), top & bottom seat post clamps and the bit in the middle (not fitted in photo).

There is also a printed socket housing which takes two Deans type RC battery plugs. One is the power cutout (you plug in a connector with the two pins shorted together) which completely isolates the batteries. The other one is for charging. I just plug it in to my charger as if it was a single 6S battery.

All up, this adds 2.2kg to the weight of the bike which is pretty good I think. Like the folding bike, I don't need much range - I've never travelled more than 10 miles on my bike so having the capacity for 100 miles is worthless to me! I would rather not have to carry the extra weight.

The Turnigy batteries have proven very good - and the two packs only cost 25 GBP each - rather better than 300GBP or so for a normal bike battery all be it with twice the capacity.

Si

 

[Cooper]

That is brilliant. You've given me an awful lot to think about...

 

[Simon Rafferty]

This is the next iteration of my 3D Printed friction drive for a 6374 motor. Apart from the throttle (and that's another story) it's fully self contained.

 

[anotherkiwi]

Damn you now I'm going to have to get back into doing some 3D...

I haven't done anything since this:

Notice how it is rendered in bristol? Nothing like being able to pick your 3D model up in your hand and look at it from all angles. The design was done in a freeware called Carene50.

 

[trex]

I would be interested in using Simon's design to develop an anti-slip roller to match the tyre tread.

 

[Simon Rafferty]

PM me your email address & I'll send you a copy! Let me know what CAD format you prefer too.

I covered the outside of the motor with self adhesive grip-tape - though it is starting to wear a bit thin.

Something that positively engages with the tread might be good!

 

[flecc]

Shades of the Zap and the Sinclair Zeta again.

 

[anotherkiwi]

Something that positively engages with the tread might be good!

And in a similar material. It would be a wear piece but you could print out spares and change as needed. trex maybe an inverted doughnut ring shape enveloping the tyre for more effective surface contact?

I went looking for some CAD software for designing my battery box. Zounds!!! Has free 3D CAD progressed by leaps and bounds since I last dabbled!!! Be still my heart, lots of studious hours ahead!

Installed FreeCAD for Linux and at 2nd tutorial I am blown away. And... it has a ship module, if only that is capable of spitting out 2D drawings for the sheets of ply...

 

[trex]

I was thinking of printing it in flexible plastic filament but wonder how to attach it to the motor's roller.
By the way, did anyone watch the Grand Designs episode where the house was designed and cut from plywood panels?

 

[soundwave]

did anyone watch the Grand Designs episode where the house was designed and cut from plywood panels.

no but thats called a shed lol

 

[anotherkiwi]

I was thinking of printing it in flexible plastic filament but wonder how to attach it to the motor's roller.
By the way, did anyone watch the Grand Designs episode where the house was designed and cut from plywood panels?

They changed the bloody satellite so my plans for a flat satellite dish went down the drain (instead of in front of the window), no freeview in the south of France without a 1.2 metre dish! I quite liked that guy and his TV show saw some lovely houses.

 

[soundwave]

get a kodi\xbmc box or stick uses wifi so no need for 1

 

[anotherkiwi]

I told you already they don't do freeview channels...

no but thats called a shed lol

You weren't listening: no sheds in straw or ply only brick, the big bad wolf will huff...