Noamsal said:
madin88 said:
i like the idea of placing the motor on the swingarm, but due to the extension you have created a weak point on the upper arms.
further do you have enough space between wheel and motor in full deflected condition? the gap looks very small and unless im mistaken it becomes a bit smaller when the damper does deflect.
i agree,
and maybe you've seen someone else extending those dropouts but it looks like he kept the triangulation of the stingarm, when you made it a bit square at the end, that makes an angle in the end of the swingarm which is reducing the strengh.
i think you should add a bar like in the added picture, you can use the dropout screw to catch it from one side and a good steel band to catch it on the other side, that way its reverseable
View attachment 1
Alot of dirt-jumpers has something like this but inside the triangle, this wont do in your situation but its a sample of what it will affect
i won't risk a frame like that especially on those speeds
personally, i wouldn't touch it. It looks like the extension has increased the leaverage on that point by about 2:1... now this bike is built to be a heavy duty downhill bike - so depending on boris's riding style he may never come close to stressing that joint even with 2x the torque on it simply because the size of drops etc that he does pales in comparison to what a pro/hardcore DH rider would subject this bike to. If it could have previously taken a 6ft drop, then with these mods it means it should still take a 4ft drop or so...
Adding a strut where you suggest will also focus the force on the middle of a span - not really a great spot to have it. You'd be better off running it up to the top point where it attaches to the shock, if you were to add anything at all.
If this was a cheap XC bike however I'd agree with you re possible failures, but unless boris is intending to do regular '4ft' drops etc (note, im not sure what would constitute 'pushing the limits of the frame' on the original bike, so 4ft is just a wild guess) I think this frame will handle the extra forces just fine.
boisrondevens said:
I'm not the best tech guy when it came to analysing specifications.
Turnigy RotoMax 150cc Size Brushless Outrunner Motor
No load current: 51.8V/5.2A
Weight: 2530g
Watts: 9800w
Turnigy RotoMax 100cc Size Brushless Outrunner Motor
No load current: 44V/4.5A
Weight: 2074g
Watts: 7992w
Turnigy ca80-80
Non Load Current: 6.0A at 20V
Weight: 1545g
Turnigy ca120-70
Non Load Current: 13A @ 20v
Weight: 2730g
Rv-120
Non load current: 7a @ 72v
Weight: 4300g
yea sadly this is what really makes me a bit weary of this motor... thats quite a high no load for what is a comparatively low rpm... and the increases aren't linear from 36-72, suggesting that its hitting the limit of its iron...
from revolt:
36V- 4.75A
48V- 5.3A
60V- 5.9A
72V-6.8A
this results in the dimentionless ratios (obtained by deviding the delta I by the delta V for each voltage step):
36-48 0.836842105
48-60 0.890566038
60-72 0.960451977
So the no-load power is increasing at a exponentially for a linear increase in voltage... where generally you'd expect a linear increase (ie, each of those 3 numbers would be roughly equal, as windage is usually pretty negligible).
the promising data i've seen is some guys in russia who've tested the same motor with a few different controllers... its hard to be sure given the language barriers and trying to see the power draw on some YT vids but it seems that a better controller (ie an adaptto) runs the motor far better - as much as 50% less power draw at no load, but I haven't confirmed the voltage he was running... you can see me asking here:
https://www.youtube.com/watch?v=iIrGe2HO2dQ
if its only drawing 200w at about 70V then thats actually very promising, as it means its probably the controller more than the motor thats responsible for the high no-load power draw...
https://www.youtube.com/watch?v=wCPxDpGVt1Q
this too shows much lower no load power draw - though its hard to know if his CA is properly calibrated...