Introduction: E-Trike Activity
So after I completed the gokart it was pretty clear straight away that as a project it would be impossible to manage as an activity for kids and I had originally planned for this.
On another visit to SUTD in Singapore, a year later I saw what looked like a 3 wheel E-scooter and knew right away that this had a lot more potential and would a lot simpler to complete with successful results.
The Trike is based on a specific type of E-Scooter, the ones that are front wheel drive. I originally used a Fastwheel F0, this was 360SGD but prices are steadily coming down. We managed to acquire 6 Aleoca E-scooters at 280SGD per piece about 200USD each. The frame is my favourite 30x30mm Aluminium Extrusion at about 30-40 SGD for 5m, the wheels are simply 4" Castors, cheapest you can find that have the four hole flange, a load of 90 deg brackets and an old chair. Because we're a design department we bought a shed load of Herman Miller(esq) chairs at 20-30SGD a piece, after 3 years of heavy use, kids leaning back on 2 legs etc, we have quite a collection of parts. The seat itself is fantastic for this kind of project as it drills perfectly and gives a little spring for suspension.
With each trike being designed and made by a group of four kids, we can keep the costs to them at a minimum and let them keep the Scooter at the end of the 16 weeks. The age ranges from grade 6 up to grade 12, so from 11 to 18 year olds.
I've attached a working drawing that shows some detailing, their is also a direct link to the Fusion 360 file should you need a closer look for inspection, but it's pretty self explanatory.
Public link to the fusion 360 file - http://a360.co/2yt7pAf
Step 1: Week by Week
The activity is spread over 16 weeks, but it took me 3 hours to work out and build a prototype prior to planning the activity, so time really isn't an issue for this project. 16 weeks allows for better planning and collaboration. Each week is about an hour of solid workshop time.
Week 1 - Health and Safety, workshop rules, 7 norms of collaboration and the overall process.
Week 2 - Anthropometrics (Tape and Paper)
Week 3 - Cutting List, accuracy and tolerance
Week 4 - Disassembly Skills - labeling, sorting and recording
Week 5 - Disassemble, Frame Cutting and Assembly
Week 6 - Disassembly and Assembly
Week 7 - Finishing and Making safe
Week 8 - Testing, evaluating, developing and improving
Week 9 - Racing and Time Trials
Week 10 - Race Comp
Week 11 - Strengthening and Wheel Change
Week 12 - Strengthening and Wheel Change
Week 13 - Physics in counter steering and Drifting
Week 14 - 15 Practice, Time trials, Racing
Week 16 - Disassembly and Clearing up.
Step 2: Week 1 and 2
With any large group in a workshop norms need to set up and explicated. When to work when to stop, location of emergency off button, safety, which tools to use with not to. I should say now that as a rule the supervising and supporting staff do not do the work for the kids, we're there to coach and questioned and simply make sure everyone is working safely. It's so easy to say "Let me do it for you" but we really try to avoid this.
The second week is all about the Anthropometrics, we give a large sheet of paper and a roll of masking tape to each group of four students and we leave it up to them to map out the plan of the chassis, I had originally planned for the extrusion to be 40 x 40 mm but after seeing the shear over engineering from each group the costs would have bankrupted us, if they were going to use so much frame then they could make do with 30 x 30 mm, it's not only the money for the extrusion but the brackets as well. Brackets for 40mm are very expensive. Once each group has got the equipment needed, they place the chair on the paper and begin to tape where the frame will be, I left my prototype lying around but it has been loosened and was in no state to operate... I wonder if this is why they all seemed to end up with tank chassis'.
The chair needs at least 3 points of contact, generally two at the rear and one at the front. The back castors also need a minimum of 3 contact points.
Step 3: Week 3
A great thing about this project is that there is no real need for power tools, a cordless drill to make holes in the seat but otherwise that's it.
Once the groups have finalised and agreed upon their chassis designs, they count up the total frame length needed, how many brackets and what types they need and put the order in. i.e. they give me a sheet of paper with dimensions on it.
I then provide them with the total length and the brackets and because I'm sick of having my tools lost and destroyed I give them a tool box and set of spanners. They set about the extrusion with hack saws, pens and engineers square (well some do!) Those who need to file do so and they use their chassis plans as a quality control tool.
Step 4: Week 4 - 6 Disassembly
Disassembly is where it'll go wrong if it's going to go wrong (out of the car-park) because of this we try not to give them the E-Scooter until this stage.
When looking to buy the E-Scooter you should be looking for a front wheel drive with all the components on the front end. You are also going to need to fix this to the frame so pay attention to the mounting brackets.
Most kids these days have phones that take better photos than a stand alone camera, you'll need to remind them though that the photo is worth so much more than they think when it comes to putting the parts back together. Otherwise crack out the masking tape and label the parts in an order.
If you have the correct style E-Scooter, then all that is needed is to remove the back end. Most decent scooters will come with a set of allen keys, these are usually crap and they'll round pretty quickly but if you're strapped for cash they'll do as long as you get a little WD40 on the bolts, these mounting bolts are usually locked in tight. You'll want a decent set of nail punches at hand if you're starting to find it difficult to remove the bracket, once the bolts are removed, the plain bearings can also play a solid put in keeping the bracket exactly where you don't want it to be. Punch these out and you'll be laughing.
Step 5: Week 4 - 6 Assembly
With half the group ripping apart and loosing all the pieces to the E-Scooter, the other half can start the assembly process. Using the Chassis plans, the cut extrusion and a ton of brackets, nuts and bolts, it's a simple case of putting all the parts together and screwing them in tight. We've started (because we're actually in mid activity.. how authentic is that !?) with fixed castors, simply because trying to control the trike with free spinning castors is hairy. Once they've learnt how to drive carefully and have tested their manufacturing skills, then they can switch the wheels over - (Week 11 for my lot).
Slide a couple of gripping flange nuts down the main centre frame and back frame before attaching the front drive module in place.
With the frame completed, minus the seat, the mounting bracket on the front drive needs to be mirrored, this can be done by flipping it around, no tools needed. In my prototype model I needed to sandwich the drive stem in-between to bars of Aluminium, this was because I use 40 x 40 mm frame, for the students using 30mm they'll most likely need a couple of washers on the frame side. To note.. it is weak and it'll feel like it, but for the forces that it'll undergo the bolts will hold it in place and you end up going into a car, wall or down a flight of stairs you should be fine.
Once all it sorted, fix the chair in by bolting through the drilled holes into the flange nuts you placed in earlier.. you'll need to poke around a bit in-order to line them up.
Step 6: Moving Around
These Scooters don't start unless the wheel is moving so you'll need to kick off, nothing too crazy, just enough to move the wheel. The pick up is fast and because you're low it feels even faster.
They usually come with an e-brake, if you're using fixed castors then it'll work fine, if you're using what I have in the video, then it's better to use your feet unless you're travelling in a straight line.. (something I am yet to be able to master!) The tire will take a pounding and you'll see it starting to shred immediately, but once it's worn down a bit, you'll stop worrying about the black marks left all over the street.
Wear a helmet and good luck.