Home made pedelec

saneagle

Esteemed Pedelecer
Oct 10, 2010
6,574
3,060
Telford
I've been thinking about this and have realised that the reason tadpole trikes have the pedals stuck out in front is to bring the centre of gravity just aft of the front wheels. As you move the rider further aft then the effective wheelbase decreases and the machine becomes unstable. A four wheeler doesn't have this problem. This is probably obvious to everyone else but it wasn't to me! A four wheeler has the problem of needing a differential which isn't easy or cheap. So I was wondering .....why not make a 5 wheeler with the motive power provided by a 5 th wheel between the two rear wheels? The outer wheels would just be on stub axles fixed to the chassis. There was an extra powered wheel made at one time for push bikes, it was hung on one side and the engine was in the hub.
You might get some ideas from this one. He made a limited slip differential out of bike freewheels in another video; however, I think he made a mistake with the brake because the wheels can still freewheel when the brake is on, and you can see that he didn't have a back brake when testing. You'd need wheels with individual disc brakes fitted to the hubs, then mounts for the calipers.

 

thelarkbox

Esteemed Pedelecer
Aug 23, 2023
1,169
358
oxon
I've been thinking about this and have realised that the reason tadpole trikes have the pedals stuck out in front is to bring the centre of gravity just aft of the front wheels. As you move the rider further aft then the effective wheelbase decreases and the machine becomes unstable. A four wheeler doesn't have this problem. This is probably obvious to everyone else but it wasn't to me! A four wheeler has the problem of needing a differential which isn't easy or cheap. So I was wondering .....why not make a 5 wheeler with the motive power provided by a 5 th wheel between the two rear wheels? The outer wheels would just be on stub axles fixed to the chassis. There was an extra powered wheel made at one time for push bikes, it was hung on one side and the engine was in the hub.
Sounds like a set of my first bike stabilisers? , lift them out of the way at speed and benefit from 2 wheel at speed stability even to improve cornering etc.. ? is it gyroscopic stability that keeps a moving bike stable??
Brain fart excuse me..

Would only require the single 5th rear wheel to have brakes too.
 

matthewslack

Esteemed Pedelecer
Nov 26, 2021
1,845
1,335
Why not a three wheeler tadpole with wide rear stabilisers? They only touch down to prevent rollover.
 

flecc

Member
Oct 25, 2006
53,135
30,556
The first reg to laminate or have linked on your phone, im old skool and have a laminator ;)
Is the definition of EN15194,,

The second is the amendment or ruling that says 4 wheels is still a pedelec and covered by epac regs.
As to what that is specifically?? I dunno?? but if no one here can cite or signpost you ?? a locally relevant legal forum might be worth a visit?
This is page 2 from the 6th April 2015 amendment to the EAPC regulations:


See item 3 (b)

(3) In regulation 3—

(b)for “bicycles and tricycles”, substitute “pedal cycles with two or more wheels”.

So you can have as many wheels as you want.
.
 
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Presterjohn

Finding my (electric) wheels
Sep 11, 2024
17
3
I've been looking further into the differential question. Early cyclecars did not usually have one, instead they used two belt drives to the back wheels. A belt will slip whereas a chain will not so I guess this solved the problem in a simple and cheap way. I could do the same, mounting the rear wheels on stub axles [using the bearings in the wheels] and a vee or polyV belt drive to each wheel from a countershaft which would carry the gear cassette, freewheel and derailleur. The polyV pulleys can be quite small, I have used them on machine drives with great success.
 

AndyBike

Esteemed Pedelecer
Nov 8, 2020
1,329
562
I like the fact its got some curves on it. Many of these type of builds come up with something that could be mistaken for postman pats van.
 

Presterjohn

Finding my (electric) wheels
Sep 11, 2024
17
3
Hi, this is going ahead. I'll post some pics when I get some bits made. I am going to make it just pedal to begin with rather than shell out a load of money on a mid drive motor. I am wondering about the braking and would appreciate some input please. It seems that most tadpole trikes have independant front brakes - is that right? Any ideas how I can get 4 brakes working with only two levers? I am using disc brakes [ I have got the wheels] . I was thinking of cable brakes.
 

matthewslack

Esteemed Pedelecer
Nov 26, 2021
1,845
1,335
I wouldn't worry about 4 wheel braking to start with, put that on the enhancements list so that it doesn't 'slow you down'. (Didn't see that coming!)

The legal requirement is two independent braking systems, not brakes on all wheels.

My tadpole has independent front brakes which work very well, and no rear brake, except a parking brake.

I would concentrate on powerful front brakes, big rotors, four pistons and hydraulics.

There are levers that operate two brake calipers, I haven't used them.
 
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Presterjohn

Finding my (electric) wheels
Sep 11, 2024
17
3
Thank you. I'm looking at hydraulic brake kits. I am thinking of using an old Peugeot bike frame I have which I will cut and build into the vehicle. This will get me the bottom bracket and derailleur mountings. I intend to fit a rear hub [ without a wheel] and take the drive from it to twin pulleys to the back wheels. I have a question about the bottom bracket. The one I have is 68mm wide and the cups that screw into it are right and left hand threaded and are 34.75mm diameter. Will this frame fit a mid drive motor kit?
 

matthewslack

Esteemed Pedelecer
Nov 26, 2021
1,845
1,335
That sounds pretty normal: 68mm is a standard width and the bore is around 33mm, so yes sounds fine.
 

Presterjohn

Finding my (electric) wheels
Sep 11, 2024
17
3
Thanks Matthew, I'm not so sure. The thread looks different. It looks like a coarser thread than the bsa ones. I managed to get apart another rusty bottom bracket and it wouldn't screw into the Peugeot threads. I read somewhere that they are not all the same. Also the square taper spindle has male threads on the ends so they would need nuts to fit the cranks.
 

saneagle

Esteemed Pedelecer
Oct 10, 2010
6,574
3,060
Telford
Thanks Matthew, I'm not so sure. The thread looks different. It looks like a coarser thread than the bsa ones. I managed to get apart another rusty bottom bracket and it wouldn't screw into the Peugeot threads. I read somewhere that they are not all the same. Also the square taper spindle has male threads on the ends so they would need nuts to fit the cranks.
None of that is relevant when you fit a crank motor because you chuck all those things. The only things that matter are the length and inner diameter of the tube. The BBS01 shaft diameter is the same as any other at 33.5 mm diameter. 68mm long is standard.
 

Presterjohn

Finding my (electric) wheels
Sep 11, 2024
17
3
Ok, that's interesting. At the moment I just want to make it without pedal assist. What kind of new bottom bracket can I buy that will fit? I haven't got any cranks or chainwheel etc. I don't want to spend too much on this because I'm eventually intending to buy a mid drive unit.
 

saneagle

Esteemed Pedelecer
Oct 10, 2010
6,574
3,060
Telford
Ok, that's interesting. At the moment I just want to make it without pedal assist. What kind of new bottom bracket can I buy that will fit? I haven't got any cranks or chainwheel etc. I don't want to spend too much on this because I'm eventually intending to buy a mid drive unit.
A standard BB (Shimano or BSA type) is 1.37″ x 24 threads per inch (approximately 34.8mm diameter). All other typres are close to that. Some older French bikes have 35mm dia and 1mm pitch (25.4 TPI), other bikes have 26 TPI. If yours has 24 TPI, you'll be OK.

The nut or bolt at the ends makes no difference. A new BB comes with the nuts or bolts.
 

Presterjohn

Finding my (electric) wheels
Sep 11, 2024
17
3
Hi, i've been making some progress so here are some pictures. As you can see I've decided to make it a 3 wheeler because I don't want to be the one to test the law out regarding whether a quadricycle is legal. I am incorporating lugs etc to make it easy to convert it to a 4 wheeler at a later date.
PA241300.JPGPA241301.JPGPA241305.JPGPA241304.JPG
 

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matthewslack

Esteemed Pedelecer
Nov 26, 2021
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1,335
Front end geometry will be hard to live with.

The steering axis needs to point at the tyre/road contact patch, otherwise there will be severe bump steer and other unpredictable unintended steering inputs.

That needs a significantly non-vertical axis in the front view, and usually slightly non-vertical on the side view too.

Castor is the name for one of those angles.

My trike has MacPherson struts, just like car suspension, with a single lower wishbone and anti roll bar.

It might be useful to fit wheels and have someone push you around a carpark to get a feel for it.
 

sjpt

Esteemed Pedelecer
Jun 8, 2018
3,814
2,745
Winchester

matthewslack

Esteemed Pedelecer
Nov 26, 2021
1,845
1,335
I completely misread that; I read it as referring to web based computer art.
My art is exceptionally hard to live with!