Electric trike "recumbent" for "3" build

[Mihai_F]

Hello community, i'm back with a new build, i seems that i like building stuff as much as riding it, so here it is.
I'm building a electric powered "recumbent" (no pedals) trike than can carry 1 adult and 2 or 3 kids, or 2 adults, the idea came because my kids really like taking them a ride with my drift trike, but since it has only one seat i can only take them in my lap, but then i can not do any fun sliding because si not safe and secure position for them... so yeah... a new fun "vehicle" that can carry 3 is needed.
I started by butchering 3 abandoned bikes to get the needed parts, then "found" the motor form a respectable brand, it is an mid drive ebike motor, and i will be powered by my own controller so only using the motor and redrive unit, some of you might cringe seeing this fine motor being butchered, but hey i need to get the full beans and more out this motor because is overbuilt and can be abused.
So i bought me self a flux-core welder and started building and also learning to weld . I made a small design in CAD to figure out the dimensions and the angles, then started "cobble-cating". I was a bit of PITA to get the ackerman steering geometry and all the angles camber, caster, toe, kingpin angle right, lots of measurements and corrections.
The rear end has suspension, the driver is in the back seat/main seat and the bench in the front (80cm wide) can hold the passengers, i elected on top handlebars steering as opposed under frame as most recumbent's have it. The brakes are mechanical disc brakes, cheep style with threads on the wheel hub, this needed securing to not unthread in reverse, and this as done with 3 bolts axially threaded between the hub and disc flange, and that ain't goin any where any more (tested it).
The pinion for the motor had 36 teeth the biggest on the wheel has 34 teeth (smallest 13t), motor has a 14,2 internal reduction, so will se how and if it will need more ore less reduction. The 13t splines on the motor pinion i cut them on my small DIY CNC, then filled the corners for a snug fit on the shaft, the retaining nut is an M25x0,75 left hand, witch i made from aluminum.
The front brakes have a cable splitter that i made so that both left and right front brakes are on the same handle
The back wheel is a 36 spoke double rim 20" BMX wheel, the front ones are stock 28 spoke 20" wheel, will see if they hold the weight, i tryed sourcing 14mm shaft hubs (for disk) but i was unable, so for the moment i'l weld the shaft nuts/bearing nut on steering the spindles to increase the inboard local thickness of the shaft(for strength), and assume that i have to cut it of if it bends or brakes rim or shaft... but so far so good.
Here are some photos, they will speak for themselves.

 

[ChapinB]

How unconventional, strange. Odd. I love it!

Welds dont look too bad, that last one depending on where it is might want a top plate though.

Maybe something to cover the steering drag link so feet dont rest on it? Or is that what the front bar is for?

 

[neptronix]

Love the creativity, look forward to seeing how it turns out

 

[AdR]

Second the creativity.
What' the specs of your frame tubing?

 

[Mihai_F]

Maybe something to cover the steering drag link so feet dont rest on it? Or is that what the front bar is for?

yep, front end still has more parts to be added, on of them is that "cover"/protection for the steering drag link, although its main purpose will pe frame rigidity in the spindles area so it does not stretch/twist outward under load, and one more in front for foot rest in combination with the one that is now there, one for back of the heels one for soles so that feet don't slide down

 

[Mihai_F]

Second the creativity.
What' the specs of your frame tubing?

the frame longerons are 50x30mm with 2mm wall tubing, some 30x20mm with 2mm wall tubing for other parts like backrest of front seat/bench, some 15x15mm square tubing for other light load stuff, and L and flat bar are 25mm with 3mm. Just regular construction steel.

 

[SlowCo]

Nice project!
Will be great for taking the kids for a ride, do shopping, etc. Are you allowed to ride it legally on the streets where you live?

 

[marty]

Frame design don't look strong. I would have a fat person stand in the middle and jump up and down to see if it bends or breaks. Bad things could happen if frame fails when trike is moving.

 

[Papa]

I'm a bit concerned about your weight distribution when riding solo - Just appears your CoG would be too far aft.

Ideally, you should have near 65% of the laden (gross) weight on the front axle, and the remaining 35% on the rear axle. I would suggest repositioning the front passenger seat forward... enough to maybe use your front 'bumper' as the passenger's foot rest. If that repositioning still fails to achieve at or near the ideal CoG location, then you can opt to reposition the driver's seat & controls forward as necessary.

A single bathroom scale under a single wheel w/matching blocks of the same height as the scales, under the remaining two wheels. Check all wheel locations on a level surface.

 

[offGridDownUnder]

i can not do any fun sliding because si not safe and secure position for them

I do not like the un-braced welded angles in the frame leading from the rear to the front wheels.

Think of the sudden (thus multiplied) forces that will occur when just one of the front wheels hits "air" on entering a pothole in the road beginning a twist driven by weight plus whatever cornering forces might be happening at that time - and then hits the following other rim of the pothole.

I expect weld failures at the steering knuckles or at the welded angles themselves. If you manage to make the welds "strong enough" then I expect frame warpage that will be quite difficult to correct. That entire front end is a flat, open plane surface with no bracing against torque loads.

Before you take your kids on it, stand on one of those angle welds and jump up and down, and see what happens. All cantilevered, no triangulation.

 

[PaPaSteve]

The fun of building stuff and then trying it out ! ! !
Please show more of your DIY CNC

 

[Mihai_F]

I'm back with updates and i'l respond to your questions and suggestions here.
1. As for road legal in my country, in theory NO, but then it's debatable, since there are tons of electric mopeds unregistered riding on streets even unregistered Sur-ron's i'v seen on the streets, so that is that..., I think that it's main use will be on bike trails, paved or in forests (loaded on the car till there).
2. The jump test, yes i've done o few of those, its all fine, it will hold really well for chill riding. It's weakest point so far is front wheel axels.
3. Weight distribution in solo configuration, yes you are right. But its intended max speed might not ever be over 30Km/h so it's handling capabilities due to weight distribution might not be a concern at that speed. Being rear wheel drive i wanted as much weight on that wheel for offroad capabilities.
4. As regard to frame stiffness, it is stiff enough, a bit of flex is desirable, being to rigid brakes stuff, i know this from my aircraft design and build knowledge and experience.

Updates: so i added the remaining structure in the front as i said in an earlier post, also added a "tail" structure that will hold the battery and tail lights. Did all the upholstery on the front bench/seat. Remade the foot rest for the driver, they are under the front seat/bench.
Also added some photos of my DIY CNC as requested. A few details, travel: X 200mm Y 66mm Z 200mm, spindle power about 300W 22kRPM with 1:4 belt redrive, steppers nema17 (42mm) 28Ncm 1,4A. Runs arduino cnc with A4988 drivers, 2 isolated supplies one for spindle one for CNC axes (both on 28V), Cross table is from aliexpress the fitted with T8 thread leadscrew, column is 70x70 square AL tubing and 12mm round fully braced slides. It can cut steed with 2mm mil, with decent finish, it can drill steel with 6mm drill.... .

Here they are:

 

[PaPaSteve]

Nice bench top mill.

 

[Mihai_F]

So we went for first testing in the parking lot, all went fine, then decided to take it next level.
Went for a ride thru forest trails, man it was fun, we went for 3 hours ride, the "rig" is quite capable with 3 pers onboard in off road.
The ride comfort was really good, the seats and the bench are comfy, they're reclined position is just wight.
Now the modifications needed for better performance:
1. A smaller pinion on the motor is a must in order to have climb performance on steep hills, now it has 36t on the motor and the biggest on the wheel is 34t, so i'l try something like 24t on motor and see how it goes.
2. install the rear derailer, and new chain, we had issues with chain falling off.
3. adjust the handle bar height, it is a bit to low
4. weld the front wheel inboard nut axels in order to gain shaft thickness, we bent them and straiten them a few times, no bueno, TBD if it will be strong enough.
5. make and loom the wiring harness out of the way of occupants, wright now there are wires every where around my seat.
6. change the brake levers, and adjust the brakes, and zip tie the cables to the frame, so far the brakes are a bit uncomfortable to squeeze because of levers being to small.
7. adjust the SW motor parameters, so far it works ok, but there can be improvements in the sonsored to sensorless crossing threshold, if there is heavy load on the motor (like uphill start) it fails to make the crossing, or if the hill is really steep and the speed bogs down at some point it looses sink in sensorless .
8. paint the frame, this is just aesthetics, but can give confidence if the "rig" looks cool

i'l add photos later.

 

[PaPaSteve]

Great progress.
FYI regarding the front axles . . . it's common to see mountain bike through axle front hubs being adapted to use on trikes.
15mm or 20mm axles.
Use a solid shaft not a hollow axle as common on a mountain bike.

I need replacement hubs like this

For many years, Greenspeed used drum brake hubs on the front of their Trikes. Now Wizwheels owns the brand (Ian Sims passed a few years ago) and my Magnum Big Wheel has disk brakes on the front. I want to build another set of wheels with wide rims. For my design, I already have the rear hub...

endless-sphere.com

 

[Mihai_F]

Great progress.
FYI regarding the front axles . . . it's common to see mountain bike through axle front hubs being adapted to use on trikes.
15mm or 20mm axles.
Use a solid shaft not a hollow axle as common on a mountain bike.

I need replacement hubs like this

For many years, Greenspeed used drum brake hubs on the front of their Trikes. Now Wizwheels owns the brand (Ian Sims passed a few years ago) and my Magnum Big Wheel has disk brakes on the front. I want to build another set of wheels with wide rims. For my design, I already have the rear hub...

endless-sphere.com

thanks for ideea!, when i was searching for used bikes/ parts at bike repair shops, i got one aluminum hub that was modified and fitted with bearings(6002rs) that support 15mm shaft, the only downside is that is 32 holes. So if i make another one, or buy 2 already made, i'l have to source 32 hole 20" rim somehow, they are 28 or 36 or 48 holes usually.

 

[PaPaSteve]

In a pinch it's possible to lace a 32 hole hub to a 36 hole rim.
Requires a creative assortment of spoke lengths and patience when doing the lacing.

 

[Mihai_F]

i'm back with photos from previous ride.
So i added another 24t pinion on the motor, and with 34t on the back now i have ~1:20 gear ratio (motor internal redive1:14.2 and 1:1.416 chain). Added the rear derailer to keep the chain tensioned, (still with the old chain, i'm cheap )
Also welded the front shaft nuts to spindle, now it is solid. Adjusted the brakes
Went out in the forest to test it, we rode it hard and climbed steep hills. The new gear ratio is outstanding for climbs (also cooler motor now), and no more bent shafts.
The weight of the "rig" is 38kg without battery, witch is good, as i can lift it by myself to put it on the car.
Now the controller settings, it's the same controller type as on my drift trike: i limited the power to 1,5kw (conservative not to cook the motor), the phase amps are set at 90A, field weakening at 12A (conservative for now) it runs on 60v lithium battery (16s).

 

[Mihai_F]

I'm back with updates. I finished the "rig", painted it, made the LV 12V system, installed lights, fenders, new chain, "loomed" all the cables, and installed the display for the propulsion system. Kids wanted yellow, i wanted blue, so half half.
Last weekend went alone on to a really hard offroad trail, i may have exaggerated a bit and pushed the "rig" outside of it's intended usage envelope but it was for sure fun, at some point climbing really steep, i pushed 1,5kw in that small (300w) motor , clearly cant be used that way without baking something at some point.
A few things i might change on it, because of the abuse mentioned above:
1. rear wheel hub i sense it needs to be changed soon, although wheel was bought new, the hub is crap quality (iron pressfit type)
2. the sprockets on the motor, i'l try put a 24t and a 20t, instead of 36t and 24t, the 36t isn't used used at all, and there is need of higher reduction ratio (20t) to climb the some really really steep offroad trails, the ones that real 4x4 offraod vehicles do .
3. The front wheel hubs, the 10mm shafts flex a bit to much on incline of the road, and i managed to bend one a bit this time
4. The rear spring with a real shock absorber, at times it gets oscillating bouncy, and if i do not slow down to stop it, something will brake.
But if i stay on light forest and parck trails it is perfect as it is , problem is, i' can't do that, i know myself

Here are some photos of "finished rig".

 

[Mihai_F]

I'm back with updates, i made a new sprocket for the motor, after doing some fancy calculations, to find out at what speed at what steepness is required a certain power and torque. So for a power of 1,5Kw at 8km/h a 255kg mass a 500mm wheel with a rolling resistance coefficient 0,1 (0.08 si wheel in sand) a 15 degree slope would require 168N/m at wheel "shaft". And that would need a total gear ratio of about 26 for my setup, so i selected a 18 tooth sprocket for motor. Yeah this is geek science stuff.

A 15deg slope is about 26,8 % slope, so steep stuff even for cars


This first calculation is to find out the wheel "shaft" torque with regard to steepness and speed, it has accounted for 500mm wheel


This calculation is to find out at what rear ratio and speed and what batt voltage at 1,5kw power what torque would yield

 

[Mihai_F]

I'm back with updates, went for a ride with kids. The new gear ratio (1-26.8) is awesome, it has lots of torque, was able to climb almost every thing i wanted to with 3 on board, but with only me onboard the limitation was loosing traction on the back wheel on an really really steep hill, witch is so cool to climb that steep. Having rear derailleur being able to use all gears, that is verry useful. Also changed the back wheel hub, the previous one was just trashed, the bearing races ware pushed inward 2mm and there was no stopping to that. After this ride i'l have to tighten the spokes a bit they got seated well now, the new aluminum hub is adequate for the job now. One new thing that is stating to "slowly fail" is the rear suspension joint, i suspected that will not last long since is on bushings, so i'l upgrade it to bearings, but first i'l have to design it, and see what it can be done there, with minimum "surgery needed". All in all was a verry successful and fun ride, we did not need to use tools or fix anything and the trike does not need immediate repairs, like on previous "abuses" .
More future plans:
I'l increase the max power to 2Kw for the next ride, and see how will that go, hopefully nothing brakes , so far on 25 degC ambient, motor went only up to 48degC, with 1,5kw limit, so there is still some room to go up , especially in cold season.
I'l come back with some photos from the ride, soon.

 

[Mihai_F]

Added photos