Descendence bikes open-source electric bike frame

[madm3chanic]

hi dudes

dont know if any of you here know me- im Madm3chanic, i own descendence cycles. its not really a business as such, i make about 10 frames a year (on a busy year, and there's a good chance a few of them will be for me), so mods please dont misconstrue this as an advertisement and delete my thread

im trying to design myself a 3.2kW 72V/20aH frame similar to a bomber or a raptor to get myself to work on, and after chatting with John Bozi on here iv realised that i would like to make it with a concentric pivot to the BB shell (iv done them in the past with pushies, so iv nutted that one out already).

basically im proposing a kind of open-source frame that i could make a few more of in the future if anyone wants one, and im open to all manner of suggestions and in all seriousness, would like the help as im a bit of a noob with ev's. id be keen to make a kit similar to the raptor but outline everything i did to make it including a full budget of the parts, how to do it yourself and where to buy them, basically so anyone can make themselves a kick-arse off-road ebike.

here's my first CAD's of the proposed frame- and i stress its really early first renders so dont judge to harshly

this is based around a 63 degree head angle, standard 200mm travel DH forks, 26" front wheel, 19" moto real wheel with a 150mm hub, a 275x90mm shock and a really decent cavity for batteries and the BMS/controller. it will get to 180mm of rear wheel travel with this shock and its a nice linear rising rate so wont blow thru its travel or bottom out (tho being a concentric it'll bob quite badly under pedalling, but frock it aint a mtb...)

im open to all manner or suggestions of aesthetics, materials, whatever, and as it progresses im pretty sure ill have lots of questions re. the build and wiring her up!

[madm3chanic]

i should probably post a few pics of some of my previous frames so you's know im not a dreamer

side shot lovemachine small.jpg (207.4 KiB) Viewed 7502 times

Photo0392.jpg (40.1 KiB) Viewed 7502 times

p4pb8641869.jpg (162.67 KiB) Viewed 7502 times

i mostly hang around on pinkbike, got about a million pics of my frame on there- http://www.pinkbike.com/u/madm3chanic/

[Drunkskunk]

Welcome to the forum.

Sounds like a good idea. Have you got a design criteria in mind? Some role you want this bike to be used for?
Reason I'm asking is 63 degrees is layed back for serious big hit riding, or big speed. But it would suck roots at single track or technical trails. And your frame render looks good, but with the battery box moved low and forward of the crank like that, where do you plan to mount the controller? With the seat that high, the weight that low, and the steering angle that steep, what roll do you see this fulfilling?

Also, 72v 20Ah is 1.4k watt hours. which is a bigass battery for a bike. 3.2kwh would be more than double that size and weight. Which were you planning?

[Hugechainring]

Question- so if this is a true open source type project, will the drawings, dimensions and specifications be public? This is very much like a frame I have been considering building myself. Sharing time and resources would certainly be a way to get the project moving.

I really like the idea of the concentric swingarm pivot. That is something I wanted for my needs. That's not a big battery. The battery I want is 22S20P 50ah, which is about 200mm X 450mm X 150mm. Finding room for it is a challenge. Why? Really high current capability, and no range anxiety whatsoever.

The nice thing about this sort of project is it is possible to adjust some of the specs because of low volume production. The swingarm might be two types, standard and extended. The frame could be standard, say with 83mm BB and wide version with 100mm BB, specs like head tube angle are easily changed.

One of my design issues is maintaining strength with a large opening in the side. I've considered a top loading or bottom loading design, but I don't have a solution I'm happy with yet.

I'm in.

[John Bozi]

No more pms
This is great to share our ideas open. To be more specific of the best part of the greyborg warp.

There is no need for gear changing so all that crapola on the handle bars extra cables and in particular derailleur can be done away with. one extra way to make removal of a pain in the ass heavy hub a bit easier is to do away with derailleurs which often also need adjusting and also there is slap, and ground clearance issues etc.
Also the single swing arm looks so simple and clean, the design should become cheaper to create too.
I'd like a few versions of this made, well for different wheel sizes and battery sizes.

It would be unique to see the first full suspension single speed frame designed to take 20" wheels, so that we don't have ground clearnace issues.
I know you are against small wheels for off road use but there are different kinds off road, and if you plan to do jumps you'll soon learn about spokes and rim replacement, so once you end up babying the rear wheel you realise it doesn't need to be 26" or even 24" like a bomber.

Single track sucks for hubs as its all low speed acceleration, so most offroad is actually firetrail.

Smaller wheel better climber, better 0-60 accelerator. At 21s I still go over 60, I'd be happy to drop my voltage to get it do 50 tops (safe speed in my books) and up my amps climb like a goat.

Hit the link in my signature to see my build thread to see what I mean.

I'd also put a small hole to sit the CAV3 flush on top but enough for the plastic extrusion to drop through with wiring. I'd make that width of the bike match the width of the cav3 or as long as the bike frame is not narrower so it looks right without the ca sticking out.

sure there are arguements about keeping the screen higher up, so you can keep your eyes on the road and the screen easier, but in reality its an eye sore on the bike sticking out up on the handlebars, and wind resistance and takes up valuable view of the path ahead.

I hope you have included 1-3cm of padding around your batteries too.

I have on my bike above.

clothe tape
neoprene
clothe tape
pvc
clothe tape
neoprene
clothe tape
pvc
clothe tape

Gives all the harder shock and suspension the batteries need. Forget all the soft pussy sponges and laytex as your dealing with 15kg of weight that would compress it before its usefull.

[madm3chanic]

Welcome to the forum.

Sounds like a good idea. Have you got a design criteria in mind? Some role you want this bike to be used for?
Reason I'm asking is 63 degrees is layed back for serious big hit riding, or big speed. But it would suck roots at single track or technical trails. And your frame render looks good, but with the battery box moved low and forward of the crank like that, where do you plan to mount the controller? With the seat that high, the weight that low, and the steering angle that steep, what roll do you see this fulfilling?

Also, 72v 20Ah is 1.4k watt hours. which is a bigass battery for a bike. 3.2kwh would be more than double that size and weight. Which were you planning?

i was working it out as 30a continuous discharge (each 72v 10ah 3c batteries, 2p config)= 60amp discharge; 72v x 60a = 4320w capable, was gonna set my controller to around 40a. am i wrong there in my calcs? i realise that it's 72x20=1.4kwhrs, but i didnt think that was how you worked out the watts you ran your motor? like i said, im a noob

as to geo, the seat is actually very low (its as low as my dh frame- if you were standing up on the pedals itd be around the height of your knees unless you're 5" tall) as it is in the pic above.
the weight on any bike should always be as low as possible to offset the high center of gravity of your body when you are on a bike.
the head angle is real slack yeah, i just like that cause thats what i ride DH im intending it to basically be an offroad play bike so im looking to the geometry of a 125cc dirt bike for inspiration. it'd be simple enough to alter the plans to make it any head angle and for any axle to crown length so you could have a 67 degree head angle and run a 150mm trail fork like a pike. but in all seriousness, personally i think you would not want a cavity that big for a frame you intended to ride XC- it'd be like trying to pedal a bathtub.

the controller is in the second cavity just below the shock mounts- it'd need lots of holes of course, but that's where i planned it to go. it could always go flat on the lower side of the battery cavity i suppose a'la bomber/raptor?

[Drunkskunk]

OK, I see what you were saying. 3.2kwatts motor power. That would be good for around 40mph.

If you're going for DH and you already run 63 degrees, go for it. Most DH run 65 to 68 degrees on 200mm forks. anything in this range would be good for breaking 40mph.

As for COG, just the opposite is true. while low COG is good for low speed maneuvering, for any kind of speed, you want the weight up high, closer to your center of mass. The Science involved is Moment of inertia. Basically, if the bikes center of mass is further from you, you have to move further to affect it, and it will react slower to your movements. That can be good if you're trying to grind your pegs on a rail and stay balanced on a stunt bike, but at high speeds, you want the bike to move as a part of you not a separate weight you're in orbit of.

The controller might work there with good air ducting. Back 7 years ago I did some testing on bike airflow. Basically a bunch of wet cotton balls stuck to the frame. The place where they dried first got the best air flow. That happened to be low on the downtube, where most high power bikes are running them now.

As for maintaining strength, that depends on how you want to construct the frame. There is the flat sheet style box like the Raptor, Phasor Cycle, and Stealth. Then there are the Box tube style frames like Dlogic and myself have built. Both have advantages.

[madm3chanic]

OK, I see what you were saying. 3.2kwatts motor power. That would be good for around 40mph.

If you're going for DH and you already run 63 degrees, go for it. Most DH run 65 to 68 degrees on 200mm forks. anything in this range would be good for breaking 40mph.

As for COG, just the opposite is true. while low COG is good for low speed maneuvering, for any kind of speed, you want the weight up high, closer to your center of mass. The Science involved is Moment of inertia. Basically, if the bikes center of mass is further from you, you have to move further to affect it, and it will react slower to your movements. That can be good if you're trying to grind your pegs on a rail and stay balanced on a stunt bike, but at high speeds, you want the bike to move as a part of you not a separate weight you're in orbit of.

The controller might work there with good air ducting. Back 7 years ago I did some testing on bike airflow. Basically a bunch of wet cotton balls stuck to the frame. The place where they dried first got the best air flow. That happened to be low on the downtube, where most high power bikes are running them now.

As for maintaining strength, that depends on how you want to construct the frame. There is the flat sheet style box like the Raptor, Phasor Cycle, and Stealth. Then there are the Box tube style frames like Dlogic and myself have built. Both have advantages.

no dh bike has run any head angle even near 65 degrees since the early nineties man! personally i do not feel comfortable getting up to speed on rough stuff with anything less than 66, just feels super sketchy any steeper than that. i get what you're trying to say re. the COG, but i think you're speaking as a scientist, not a rider. if you try to corner with a higher center of gravity you lose traction much easier and it is much harder to flick the bike (especially in the air). it may be true for a short travel road motorbike (i aint no expert there) but you really need to trust me when i say its about as far from the truth as you can get for anything intended for off-road use, or in that matter anything that you intend to corner properly. iv been making/racing bike frames for 15 years now, you learn a thing or two about bike handling in that time.

if you dont believe me, try cornering a bike with stupidly high bottom bracket (like a little tallbike or something), and then do the same on a road bike or a dh frame with a low bb as it squats into its suspension from the downward force caused by cornering. you'll be astounded at the difference, and it is almost entirely due to your COG. the taller bike just makes you feel like you're about to fall over, whereas the lower frame can lean over much more, so you can dig into turns without feeling like you're about to either lose wheel traction or just fall over.

i must admit tho im a bit worried about the strength thing; actually more the stiffness of the structure. big box structures are farily stiff but when you take out all the guts of them (as you would have to do to allow the battery into it) they get all floppy. also the weight of that much 1.6mm steel is kinda horrifying (7.5kg for the front "triangle"). i did a tubular frame for my last ebike build which worked well, but im struggling to see how i can make it lok any good for this big a bike. aesthetics are as important as function to me cause in the end even if your bike works great, if it looks like shit you dont wanna ride it.

[John Bozi]

If I could build I'd just make the triangle the base top and bottom and put a abs plastic box in it, much lighter and if your going to work on this thing mainly you aren't going to be doing crazy riding, it's easy to secure a box on bike that is going to go on road. Would be nice to have a removable battery box too.

[Samd]

Quality work mad mechanic.

Good to clarify the open source part, you might enjoy this thread.
http://endless-sphere.com/forums/viewto ... ka#p906542

You'll find the frame margins pretty low here though compared to rotorburn.

[madm3chanic]

yeah i was thinking that about the removeable box too. but im mainly making it for off road riding- i have trails about %90 of the journey to work- i live up in the eastern hills of perth, if that means anything to you. ABS can be manufactured crazy strong tho, easily strong enough to handle any abuse i could dish out to it. it is after all what they make fenders and shit out of on dirt bikes and they dont seem to break all that often, so i dont see why it wouldnt be strong enough for a battery box. either that or aluminium purely for a fabrication sense; im not sure about having stuff made in plastic. i suppose i could have it made by an injection moulding place or something like that??

[madm3chanic]

Quality work mad mechanic.

Good to clarify the open source part, you might enjoy this thread.
http://endless-sphere.com/forums/viewto ... ka#p906542

You'll find the frame margins pretty low here though compared to rotorburn.

holy shit looks like he's already done exactly what i wanted to do hahahaha ahh well. bit hard to read his website but

that thread is actually really awesome, i got a heap of pointers just by looking at his pics. the main one being that he's done the swingarm as a URT rather than a concentric pivot, which is actually much more simple. i didnt even think of doing a URT cause no-one reputable has made a URT bicycle for many years due to them being wiped out by the specialised horst link at the time, but i cant really see any reason why it wouldnt be fine for a biuke like this that is not placing too much emphasis on pedalling efficiency.

making it as a URT would make slightly less room for the battery cavity and would require an extra axle, but it would mean that there would be no lathed components required to construct it (you could make it entirely from off the sholf steel and bearings and laser-cut components). using lathed components really does add a heap of headache unless you actually own a lathe yourself cause invariably they end up too small or too big the first time and then you gotta pay to have them done again etc etc...

[Hugechainring]

The frame design I am leaning toward at the moment is the sheet metal box with a round, tubular "backbone" that runs from the headset down to the BB. If the backbone is on the top side vs the bottom, it can reinforce the upper shock mount, which is pretty stressed. If the backbone is nearly strong enough on it's own, the box strength and rigidity becomes less important. Any lower connections between the BB and the headset tube are mostly in tension, and can't buckle, except possibly under the weight of the battery.

This is sort of the way the 4motus frame is designed. IMO the proportions are off a little on it, and it looks to have falling rate rear suspension. The seat position is not very adjustable, and the seat tube angle is way off, but it is a solid machine. EDIT, photos of the newer versions of the frame shipped to customers vs the promotional pics on the website look to have improved seat tube angle.

I would really be cool if the BB was bolt-on with an adjustable mount, so adjustment for height and/or fore and aft could be accomplished, but that would add weight and complexity. At least for me, most bikes are too short on the top tube, and while I can move the seat back or the bars forward, there is nothing to be done about the BB location.

As far as materials go, 4130 Cro Mo is my go-to. You can get high strength and rigidity with thin wall sections. I dislike aluminum because it turns to mush post weld unless you heat treat and/or age harden it, and it is difficult to repair or modify.

Aesthetics are important, but if you have an e-bike whose performance is awesome, you quickly stop caring about how it looks. Bozis small rear tire may look odd, but the performance makes you forget all about it. My tire of choice is a 16" moped or small dual sport.

For my use, I prefer the weight down low. The center of rotation when banking into or out of a turn is at the tire contact patch, and the closer the CG is to that point for me the better. More "flickable" as you say, and I find it more controllable when you are on the edge of traction.

e- bikes are heavy, but they don't have to be outrageous. Good designs can weigh less than a boat anchor. The Raptor 140 is advertised at 10.1KG., which seems pretty reasonable.

My personal goal is to try to identify all desired features of the Stealth, Phasor, Raptor, Greyborg, 4motus, Chaika, etc, and pick my compromises. It will always be a compromise.

[madm3chanic]

good post that one. oldschool moto frames had a similar kind of curved singular downtube with all the mounting tabs for the engine coming off that from the underside, it sounds like you're sugesting something like that. i actually really like the 4 motus frame in terms of aesthetics, its one of the nicest and most interesting frames iv seen around. i hear what you're saying about the terrible geometry tho- the head angle is retardedly steep, looks about 69-70 degrees to me. would work ok on the road, but descend a fire trail on that thing and you're asking for trouble. also that weird seat tube angle is only gonna give you an extremely limited range of seat height adjustment which is bad if you're too tall or have shorter legs than the frame is designed for.

googling 4motus i also found this thread- http://endless-sphere.com/forums/viewto ... =6&t=29555 which i think is a damn good job

as to the BB bolt on thing (and the question of geometry/wheel size in general) i tend to be quite lax about geo and frame options as if i want a specific geo frame or a different wheel size, i just make the frame like that. if this were a truely opensourced frame and someone else wanted to make one, it would simply be a matter of modifying the geometry or the swingarm to suit.

i think one of the main issues that i can see for current frames like this is that they all seem to be made in only one size (i have yet to see an option for different top tube lengths etc to suit different height riders) which is really mystifying to me- there is no such thing as a one-size-fits-all bike frame. how could a 5' 2" rider use a frame made for a 6" rider comfortably? doesnt make sense

[Hugechainring]

Yes, sort of. If it were me, I would probably weld the equipment box onto the backbone. The "motoped" frames are built like you describe with the tabs and all, but the quality is so-so and they are pretty heavy. (cheap, heavy wall tubing), and they are designed for an ICE.

A good example is here:

http://endless-sphere.com/forums/viewto ... 28&t=62040

Might be some ideas hidden there.

I like the 4motus. It's just not close enough to what I want for me to purchase it. I went back to the photos and one item I didn't address is the short swingarm. Bikes with a lot of torque will put you on your arse with the seat that close to the rear axle.

I agree with the sizing thing. Unfortunately these frames are such low production with low margins that the builders just don't offer any thing but the "one size too short" version, or in the case of the Greyborg, ship a stepstool with each bike Very understandable, though. It's a business, and too many choices costs money.

It is a difficult proposition, but I believe it is possible to offer different frame sizes while sharing many common parts. Initially, though, what happens is you end up picking a layout, and then your beta testers give you a bunch of feedback. That's kind of what's going on with the Raptor line.

[madm3chanic]

for me personally, if i am making a tube-based frame like a typical mtb frame, its no different at all to make each frame different geo; it costs no more in materials and only takes marginally more time. with a frame tho that was mostly composed of pressed steel sheet and welded into box structures, you couldnt really do custom geo cause id imagine youd have to change most if not all of the pressed pieces, thats probably the biggest issue with that sort of frame.

on another matter, does anyone know if plastic battery boxes of any sort of pre-existing size/shape are available anywhere?

[AussieJester]

Only one question..your making this for purely off road? Why are you intending using a hub motor?

KiM

[Ohbse]

This is an exciting prospect and is of huge personal interest.. the basic specifications you've described are exactly what I'm looking for in a custom frame. Personally my favourite of the currently available commercial frames is the 4motus based primarily on styling, however I've had reservations that others have touched on regarding geometry. Price and availability are also a little harder to deal with.

Cromotor capable, crank centric pivot for swing arm, ability to deal with smaller diameter wheels, ability to carry a decent amount of lipo (1.5-2kwh) and high speed stability are critical for my application (fast road/commute)

Very interested in contributing once I have a moment

[madm3chanic]

Only one question..your making this for purely off road? Why are you intending using a hub motor?

KiM

too much to fit into the front triangle bro! that really all- just trying to fit all that shit into the front triangle is a fukn mission. dont get me wrong, i wanted to at first so i could reduce the sprung weight of the springarm, but about the only way i could see it all fitting is if i used one of them lovely little motors that the Dogati has in it (the name escapes me now) but it really does add a heap of complexity and cost. plus i really would like it to still have pedallable cranks in case you ride past the constabulary.

iv been rethinking the aesthetics a bit cause i love the look of them other ones i posted- i sketched this up on the old puter as a prelim to a cad model-

3kw ebike - Concentric v2.JPG (151.4 KiB) Viewed 1604 times

gives you the general idea of what im thinkin...what you all think? the cells shown on it are 38120s cells for a 70ish volt 20ah battery, heaps of room for themn

[Hugechainring]

I like the concept. While I have your attention, could you briefly explain why the Phasor and Raptor have the swing arm pivot positioned high and forward from the BB? Is this an anti-bobbing design, or does it have to do more with the rear geometry?

[madm3chanic]

I like the concept. While I have your attention, could you briefly explain why the Phasor and Raptor have the swing arm pivot positioned high and forward from the BB? Is this an anti-bobbing design, or does it have to do more with the rear geometry?

two issues there- pivot height according to the bottom bracket, and pivot distance relative to the rear wheel.

single pivots (be them linkage driven or monopivot designs) all need to strike a balance between anti-squat properties, rate of shock compression and axle path, and these can all be altered (or are entirely dependent on, in the case of axle path and antisquat) the location of the pivot.

pivot height relative to the chainring-
if the pivot point is quite a way below the top outer diameter of the chain ring, it'll obviously try to squat forward when you pedal because of the force pulling on the rear hub from the chain; conversely put it further up and the vector of the force diminishes and you get less squatting effect. put it too high and you get the reverse occurring (as well as excessive chain lengthening which is bad for obvious reasons), which is why really high pivot point frames usually employ either an idler gear to re-direct the chain or a jackshaft system. this point is gonna become extremely important in the case of a mid drive, as the suspension may squat under engine drive; when suspension is squatted, it will begin to "stiffen up" (as it compresses the spring), so if it is too squatted it wont feel as active to bumps as it should.

pivot distance from the rear wheel-
axle path (the path that the rear wheel axle follows as the suspension compresses) has a lot to do with how much feedback is felt by the rider thru the frame (i.e how well it is perceived that the suspension is working- its not really the case but it does feel like it to your legs); a more rearward axle path moves away from the bump as it is travelling over it so you perceive less feedback (shock transferring thru the frame into your legs). that one is contentious tho as effective suspension action is as much about negative travel as it is positive travel (ie the wheel moving down into a hole from its squatted, neutral position), so its also a bit of a balancing act. one advantage of higher pivot points is that the tire moves further away from the seat as it goes thru its travel so you can have you seat lower without having wheel buzz, tho that isnt something that moto riders would be aware of.
also the further forward the pivot point is, the more movement that the member can achieve on the shock attachment point- sometimes you quite simply could not achieve enough compression on a shock at your desired amount of travel with a pivot point closer to the back of the frame, so to prevent you needing a really short shock and a very high compression rate (bad for other reasons but thats getting a little off topic) the pivot point can be moved forward.

[Hugechainring]

Thanks. I'm going to read through it a couple more times to get it in my head, but that helps tremendously. The idea of the rear wheel moving away (laterally) from the bump during compression makes total sense to me.
I appreciate your real world descriptions. In my mind, rider perception is more important than physics sometimes. Most cyclists couldn't care less where the virtual pivot point is, for example. They just like a bike that they feel rides well.

[Ohbse]

iv been rethinking the aesthetics a bit cause i love the look of them other ones i posted- i sketched this up on the old puter as a prelim to a cad model-

3kw ebike - Concentric v2.JPG

gives you the general idea of what im thinkin...what you all think? the cells shown on it are 38120s cells for a 70ish volt 20ah battery, heaps of room for themn

Love the outline of things.

What are you doing to do the drawing? Any chance of sharing the document so I could potentially play with battery sizing?

Of particular interest to a lot of us contemplating high power builds is compatibility with 18650 cells or alternatively 5s/5ah Lipo bricks. Personally the configuration that I arrived at is 21s8p or 75.6v nominal, 20ah

[madm3chanic]

iv been rethinking the aesthetics a bit cause i love the look of them other ones i posted- i sketched this up on the old puter as a prelim to a cad model-

3kw ebike - Concentric v2.JPG

gives you the general idea of what im thinkin...what you all think? the cells shown on it are 38120s cells for a 70ish volt 20ah battery, heaps of room for themn

Love the outline of things.

What are you doing to do the drawing? Any chance of sharing the document so I could potentially play with battery sizing?

Of particular interest to a lot of us contemplating high power builds is compatibility with 18650 cells or alternatively 5s/5ah Lipo bricks. Personally the configuration that I arrived at is 21s8p or 75.6v nominal, 20ah

i can share the entire 3d model or parts in either IGS STEP or STL format if anyone wants them.

im personally gonna stick with headway LiFePO4 cells myself just cause of the ease of charging them and the safety so im gonna make the cavity 120mm wide to allow three cells side-by-side, but when i initially started looking into making this bike i was gonna use 4s 10ah 20c lipo bricks. i found i could make the 72v/20ah with about 2/3rds of the room that the headway cells will take up, so you could make a seriously compact unit.

[Ohbse]

Yes please - would love to have a play. I'm not even on the same plane of existence regarding geometry or the ins and outs of frame building, just hoping to expand my knowledge and hopefully contribute something worthwhile

One thing noted in the development of the Raptor frames etc is that 150mm width allows you to have a variety of standard Lipo packs able to lie across the frame, this allows for some pretty stunning battery capacity without much fuss. Not required for everybody and certainly at the outer limits of what's comfortable to pedal around, just worth accommodating if at all possible. Ideal for me personally is total width of ~140mm. It would allow for two 18650's end to end and makes pack construction pretty straightforward. Of course with the smaller cells you can arrange them all sorts of ways, just works out a little more efficient that way.