xKillah - Enduro eBike

BigBlock

BigBlock

100 W
Joined
Jun 3, 2021
Messages
121
Location
Italy
Hi,

after having completed my first stand-up scooter project, I thought it's time for a new challenge...

My new project is ispired to the popular Sur-Ron bike, with the aim to do something better that anyone can build by himeself (at comparable Sur-Ron price) with better components, more performance, flexibility to custom modify it at own preference and definitelly with much more fun.

I'm used to say, it gonna be the "Surron Killer"... Like the Sur-Ron, the bike will have low weight (about 50Kg) to keep the nimble feeling of a MTB rather than a dirt bike.

I've just started the design, but want to post here so that hopefully I can get valuable feedback from the community.

This is the initial mockup with key dimensions:

x-Killah-mockup.png
 
Some initial specs:
  • Billet Aluminium 6082 frame (about 7Kg) with no welding
  • Simplified manufacturing - frame components machinable with 3 Axis or water-jet CNC
  • 3Kw QS Motor 138 70H - air cooled
  • ASI BAC 4000 Controller
  • 72V Battery Pack
  • Improved Sur-Ron rear progressive shock geometry
  • Two-step reduction chain transmission (primary: 1:2.2 - secondary 1:3)
  • 370Nm peak power
  • 85Km/h max speed
  • Weight: about 50Kg
 
Hi, impresive project, your front frame is in one part? do you have another view where we can see more? don't really understand how do you plan to mill the frame.
 
rider63 said:
Hi, impresive project, your front frame is in one part? do you have another view where we can see more? don't really understand how do you plan to mill the frame.
Click to expand...

it's different parts bolted togheter; making a solid headtube connection without welding it's a bit triky. I have to do some FEM analisys before committing on the type of joint.
 
Too bad the QS motor with build in reduction won't fit.
An adhesive between the head tube and frame plates could assist tremendously in
fixing them rigidly together.
 
why don't buy sor ron motor?

https://fr.aliexpress.com/item/1005002965248461.html?src=google&src=google&albch=shopping&acnt=248-630-5778&isdl=y&slnk=&plac=&mtctp=&albbt=Google_7_shopping&aff_platform=google&aff_short_key=UneMJZVf&albagn=888888&isSmbAutoCall=false&needSmbHouyi=false&albcp=11232052496&albag=110473450015&trgt=990886274862&crea=fr1005002965248461&netw=u&device=c&albpg=990886274862&albpd=fr1005002965248461&gclid=Cj0KCQjw-4SLBhCVARIsACrhWLX4WzAUK5oIpBjzR8uEj1OFWbvsGxbPT3vnaxyxHcji1aM1eSm5DLIaAon7EALw_wcB&gclsrc=aw.ds

you can also buy the lmx bikes motor which is also very compact:

https://lmxbikes.com/index.php/produit/moteur-60mm-1200w-sonde-temp/
 
I'm doing good progress on the 3D - still need to work on few details, bearings and tollerances. Any hour spent on this tage is usually 3 hours saved during build....






Quite happy with the size of the battery pack that is definitelly bigger than Sur-ron and better integrated in the frame with a lower COG.

I have managed to fit 5 stages of 18650 cells for a total number of 280 cells in a 20S14p configuration. The external plastic box will be 3D printed.

 
good to see another ~50kg build

consider also the motor i'm using the QS 120 70h. smaller, lighter, and doesn't need a 2-stage reduction (low kv of 38). never gets hot using my 120A controller so i think it could be overclocked quite a bit more but at just 120A it's already burnout capable

if i were to build a version 2 of my bike i'd definitely avoid an external 2-stage reduction and pick the 138 v3 (gearbox).

[youtube]EthQFu6oXUY[/youtube]
 
Your CAD drawings are awesome. Going with a completely bolted together bike will be really interesting.

Placement of the battery with 3D printed box is really nice -- one challenge to consider is making sure your wiring is waterproof, my current approach is enclose everything into one single unit but that has other limitations.

Another lesson learned for me was to watch out for torsional flex in the swing arm. What I found was that an extremely rigid cross piece makes a lot of difference. What thickness will the arms be on your swingarm?

F8aFZtE.png


great work -- keep posting pics!
 
the type of design I use is based on billet piece of aluminium that have stronger and stiffer properties when compared to sheetmetal or tube welding fabrication. The disavantage is more weight if not proper engineered, because usually you have a lot of useless material where not needed.

I use FEM calculation during the design process to select the proper thikness, joint type and remove material to reach a reasonable weight to performance ratio.

Here is an example of analysis on the swingarm at current stage of development when subject to 5000N of force (500Kg) - the deformation is way under the limit for 6082 aluminium (275 Mpa) - It gonna be really rock solid....



 
Do you have a simulation output for torsional flex as owhite described? I have to agree with him that while it may be plenty strong in direct load it looks rather twisty.
Click to expand...

agree with your concern. Looking at your diagrams with arrows showing the force, I think the question is what will happen if you model exerting force upwards on one arm, and downwards on the other?
 
the complete swingarm design is based on 3 cross steel rods that connect through a spacer the two arms and that will add stiffness to the whole assembly. The bottom rod is placed as close as possible to the wheel.... there is no any further space to cross-brace the swingarm in the rear area, where the wheel has to spin.

in motor bike racing, the usual benchmarks for swing-arm design are based on lateral and torsional stiffness. Typical values for the lateral stiffness are between 0.8 and 1.6 kN/mm and, for the torsional stiffness are between 1 and 2 kNm/°.

Here we are not dealing with a 100+ kg motor bike, thus lower values should be acceptable.

The current swingarm design has a very good torsional rigidity (2,240 kNm/degree) while it still suffers on the lateral loads - here the issue is not the swingarm layout, but the separate pieces I designed for the chain tensioning (to save on manufacturing costs).

I need a couple of more iterations to improve rigidity in that area.



 
BigBlock I think your simulation setup are wrong, don't lock the movement of the shock fixation. because shock will not take any torque or lateral force in real life. Just lock the main pivot in all direction ( and rotation), if your force are correctly apllied, it will don't want to rotate around main pivot and don't generate parasite constrain. Hope you will understand what I mean with by poor english.
 
rider63 said:
BigBlock I think your simulation setup are wrong, don't lock the movement of the shock fixation. because shock will not take any torque or lateral force in real life. Just lock the main pivot in all direction ( and rotation), if your force are correctly apllied, it will don't want to rotate around main pivot and don't generate parasite constrain. Hope you will understand what I mean with by poor english.
Click to expand...

I understand what you mean and it's a good point - I thought a lot about this. You are right, in a typical setup the shock mount should not be constrained for lateral and torsional simulation. But, here things are more complicated. The shock layout I'm gonna use follow the Surron design of a a sort of A-Arm attached to a progressive link - this sort of "triangle" holds the swingarm in the lateral axis and allow just for vertical movements. That's why I beleive it's more accurate to keep this lateral contraint on the shoch mount as I did.

hope this image makes more sense:

 
by the way, I did calculations also without the shock mount constraint and the results are quite similar. This is because the loss of rigidity starts on the rear half of the swingarm, where the wheel does not allow for trinagulations (see colors in the FEM images below)
 
by the way, I did calculations also without the shock mount constraint and the results are quite similar. This is because the loss of rigidity starts on the rear half of the swingarm, where the wheel does not allow for trinagulations (see colors in the FEM images below)
Click to expand...

I think your design is great but now that i see there's basically just two bolts between each arm, I'm going to make the prediction that when you put it together you be able to put one hand on the top of the back wheel, and another hand on the bottom, and by applying torsion to the swingarm it will easily twist by 10cm.

ufJLHWb.png


on my original swingarm, rather than bolts I had 6mm thick aluminum plate, and it had a huge amount of torsional flex.

7egORfy.png
 
the bolt you see will be joined by 30mm outer specers that will pack the whole assembly when properly tighten - I will share more detailed image later
 
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