Downhill project motorcycle transmission

ksithumper said:
Funny you should mention the Kawasaki KX65, that's exactly the gearbox I have chosen and in fact the postie turned up with the bottom end today ! A bargain at less than US$25. Bet I don't stay that lucky for long :D

My self-set challenge is to get a 2 (or 3?) speed box all in the right crankcase half, so it stays very narrow. Obviously I will need to shorten shafts etc. The crank space is 80mm diameter, spot on the Astro motor casing , if that is what I end up using. (I'll set a new build thread up, and stop hijacking yours!)

Most small four strokes don't have a materially wider rev range than the two strokes and the ratio spread is probably of the same order. Some have pressure fed gearboxes, so best avoided...I think you made a good choice for the power you have. Your bike looks awesome already.,
Click to expand...


Look forward to read your thread. Make sure you put a link to that thread in here, will make it easier to see when your thread goes live.
 
So I set off with camera affixed to my little old helmet and hit the trails out the back........ hard........ rather. After warming up my mojo, throttle was fed the electric lust juices and there was pretty much no one around. This thing is still bloody quick and I've been pushing it harder lately and getting to know its personality, which it seems has almost too much of.
It isn't actually the easiest bike to ride at high speed in that it's so twitchy. A bicycle isn't designed to be powered from the rear, not like this anyway and unwanted wheelstands are a constant folly due to the uber short wheelbase.
I rounded this corner ripping along at a good rate of knots, had the bike cranked over and wound open the throttle, it just wheelies (while laid over) I kept going straight and smashed straight through and old dead fallen gumtree! No big deal, a few broken branches and leaves and shit going everywhere, I pulled the bike free as it'd almost made it out the other side anyway. This'll be good the camera was still running. Off I went and hit the hills. After wicking it through the grassy sections I headed up this long steep grassy hill full throttle in 3rd leaning right over the bars. Bad move, hit a few bumps under hard acceleration and I just couldn't for the f#%@ of me stop it wheel standing(didn't hit the rear brake quick enough) and proper flipped it up the hill and went down in a cartwheeling screaming heap. Decent get off and bruised my leg up a little. Put the chain back on and finished off the battery down to about 42v, my leg was a tad sore.
So I got back home and the bloody memory card went full in the first minute!!!!!!!!! and was super shaky and crappy anyway, so no footage. Don't worry I'll crash it again.
This all means that a wheel base extension may well be worth a look, interestingly an RMZ450 (my old bike) runs a full 400mm longer. The Trek being 1100mm and most MXers are 1500mm so even 100-150mm may settle the frame and make the front end more controllable. Another thing is the C of G is much higher on a bike like this, partly due to the wheelbase but also the lack of low mounted bulk as in a dirt bike. It's much more difficult to powerslide as well and it's still very natural for me to want to lean forward, open the throttle and steer the bike with the back end. The Trek just grips, wheelies and goes nuts, hardly boring let me tell you.
I fixed the chain derailing issues and now she comes off no more.
Awesome fun this rig and I knew somehow that it'd be running a different set of rules. More playing about, more crashes and another crack at the helmet cam
 
You'll need it bro. If yours is longer and with the batteries acting as counter weight it may be more manageable......but I doubt it. With 25kw you might have to gear it for 160 mph to tame it
 
I remember when turbos entered the scene of old Gixxer R 1100. People thought of them as wheelie prone with ketchup effect. Many of the turbos had to retrofit stretch swing arm to keep front wheel down.

I think your dual drive will have the same sensation, and the same desire to keep front wheel up high. Sure it will be a true riot to ride.
Scary fast is about right.
 
Add A gyro sensor and dial back the throttle over a threshold angle to prevent loop outs or make it so you can hold a wheelie at a certain angle that could be fun. It would have to only come online at an angle you wouldn't see while climbing a hill or rate based so if cutting the throttle doesn't show a reducing angular response it stops cutting the throttle so you don't lose all your power on hills.
 
Nacent said:
Add A gyro sensor and dial back the throttle over a threshold angle to prevent loop outs or make it so you can hold a wheelie at a certain angle that could be fun. It would have to only come online at an angle you wouldn't see while climbing a hill or rate based so if cutting the throttle doesn't show a reducing angular response it stops cutting the throttle so you don't lose all your power on hills.
Click to expand...

I tried it with a Futaba GY401 about a month ago. It does not work as you would think. It just makes the throttle response really weird. I think the moment of inertia is too different from what the gyro was designed for.

Matt
 
Yeah it would have to be set up as a critically damped PID it would be weird if it oscillated around your set point. It would have to have a similar control system to one of those 1 wheel bikes but instead of being fixed to a vertical orientation there is a range of acceptable orientations and it keeps it in that range by modifying the throttle signal. It would be relatively easy to set up with a arduino and six axis imu, it would go inline with your throttle wire and modify the signal as you approach the set point. The only difficult part would be setting the PID parameters as they would vary from bike to bike. I know they make such things for motorcycles http://www.gripone.com/en/gripone_p3.htm so its definitely possible and probably easier with electric engines.
 
You would need to combine gyro sensor swith an accelerator sensor, like they do on the Sagway.
And programming it can make you anti-wheelie or wheelie hero - keep front wheel on the ground or elevated at balance point for as long as possible :D


I don't think you will be able to get it to work with 1 gyro sensor alone, you might need several. Also make sure to get quality sensors, like automotive standards. Placement of sensors likely will be critical to get fast enough response.
You might wanna combine it with the regen switch so that a wheelie over certain angle will force a certain regen to push down the front wheel, that would be faster and more forceful then easing of the throttle. Similar to hitting the back brake. Except automated.


1 sensor in the very front of the bike would have different reads then one say in the rear hub, or the on the seat post. So using several and play around with placement will get you there - but you surly would need to combine it with accelerator sensors for the fun factor.
 
Nacent said:
Yeah it would have to be set up as a critically damped PID it would be weird if it oscillated around your set point. It would have to have a similar control system to one of those 1 wheel bikes but instead of being fixed to a vertical orientation there is a range of acceptable orientations and it keeps it in that range by modifying the throttle signal. It would be relatively easy to set up with a arduino and six axis imu, it would go inline with your throttle wire and modify the signal as you approach the set point. The only difficult part would be setting the PID parameters as they would vary from bike to bike. I know they make such things for motorcycles http://www.gripone.com/en/gripone_p3.htm so its definitely possible and probably easier with electric engines.
Click to expand...

I actually built (and ride daily) a one wheeled Segway [of sorts] using a GY401. The gyro makes it rideable, but it is not easy. When I added the gyro to my e-bike, it was terrible, no matter what I did with the various settings.

Matt
 
recumpence said:
Nacent said:
Yeah it would have to be set up as a critically damped PID it would be weird if it oscillated around your set point. It would have to have a similar control system to one of those 1 wheel bikes but instead of being fixed to a vertical orientation there is a range of acceptable orientations and it keeps it in that range by modifying the throttle signal. It would be relatively easy to set up with a arduino and six axis imu, it would go inline with your throttle wire and modify the signal as you approach the set point. The only difficult part would be setting the PID parameters as they would vary from bike to bike. I know they make such things for motorcycles http://www.gripone.com/en/gripone_p3.htm so its definitely possible and probably easier with electric engines.
Click to expand...

I actually built (and ride daily) a one wheeled Segway [of sorts] using a GY401. The gyro makes it rideable, but it is not easy. When I added the gyro to my e-bike, it was terrible, no matter what I did with the various settings.

Matt
Click to expand...

Think you should have opted for more then one sensor or maybe different sensors. Adding throttle ease and regen will make it bullet proof. And combined with accelerator sensors you can dial in every parameters. No wheelie, a tad for fun or a lot for the thrills.

Have you been to big auto shows the past years? They often have those "wheelie simulators" often an e-bike attached to cheap "dyno" roll for rear wheel. And to avoid flipping they use wire or rope :D
But you could easily use a setup like that to tune your system to get the correct settings without flipping over.
 
Hi Eco,
Great that you have it going and performing well.
I had been trying to guess what my (and other) high performance e-bike would be like to ride, and had realised about the higher centre of gravity and shorter wheelbase compared to a dirtbike, so your analysis of the experience sounds pretty much what I expected. Interesting that you get so much grip at the rear while accelerating.. I guess the high centre of gravity means more effective weight shift to the back wheel while accelerating, giving good traction.

I guess that unless the wheelbase was extended quite a lot, e-bikes will never be able to climb hills as steep as a dirtbike can.

Suddenly I am happier that my motor mounting has pushed my wheelbase out by 100mm or so, and confirms my plan to mount the batteries on the bike, as low and far forward as possible. It also sounds as though smooth throttle control is important (and fast reactions) ...

As my grandfatherly bones probably break easier and take longer to heal than they used to, sounds like I should consider some armour.. even now I find it hard to resist trying that slightly steeper hill etc, to find the limits of whatever I am riding, so when mine is running I guess I will be having a few unintended meetings with planet Earth..

Hope the video camera is in a better mood next ride.. looking forward to the video.
Dave
 
i know the crazy fear of riding a bike like this....twin astros :mrgreen:

and the seeming ridiculous grip DH tyres get compared to dirt bikes, i actually ripped the sidewall on a tyre that wasn't pumped up to 40psi, ripped the valve stem out of the tube as it spun on the rim.

I had a go at figuring what a frame stretch would feel like (by taping 2 x 2litre milk bottles filled with water on each fork leg). Apart from it making the steering heavy it really didn't make it any more docile. Do you think your suspension squats when you power on?

Get a gopro....so we can see the carnage :lol:
 
Thanks for all the feedback guys, most encouraging. I don't think this kind of power is particularly dangerous, it's perhaps more a case of adjusting riding style and modding the bike a little to suit. A properly trained A grade motocross or enduro racer wouldn't back down from power like this, they'd love it.
Mr Drum, I think adding 100 or so mm to your wheel base will turn out to be a massive advantage and am keen to see how yours comes along.
As I may have mentioned I ride a supercharged 1000cc V twin sports bike and it wouldn't have short burst pick up like the Trek, as quick as the street bike is it just can't deliver instant torque like the electric motor can it would seem. I feel it's that instant torque that is doing the wheel standing. It's the instant and smooth bit that still has me stumbled.
I managed to get the video up on you tube, very scratchy though and the short run from crossing the log to the top of the little hill was a demo in 1st the rest was 3rd.

This tablet is still doing my head in and as brilliant as I may seem I can't download from YouTube without getting angry, so search 'Electric Trek Astro powered KX80 gearbox" for 1.5 minutes of amateur vidness.
 
I would put my money on how the controllers works and thats the main cause of the issues .. RC controllers have no current limiting , if you extended the wheel base yes it will tame it down a bit ( but not enough ) but then you will have more chance of popping the controller. I have gone though all this and have come out the other side. Yes the power to weight ratio is nice but you do need away of controlling it reliably for any sort of technical riding
 
That's a very interesting point. The ability to wheelstand effectively 'unloads' the system, correct? If it was held down so to speak then it would be under greater load for longer causing popping dramas.
Matt suggested that re jigging the settings on the controller will also help. I've got mine on light switch mode as it turns out.
 
Ecobogan said:
That's a very interesting point. The ability to wheelstand effectively 'unloads' the system, correct? If it was held down so to speak then it would be under greater load for longer causing popping dramas.
Matt suggested that re jigging the settings on the controller will also help. I've got mine on light switch mode as it turns out.
Click to expand...

Yes.. as the front wheel comes up to the balance point the load get less so motor speeds up ( due to the less load ) then before you know it you are off the back ,, so just before and just after the balance point it becomes impossible to modulate the throttle.
 
A short wheelbase certainly has its own advantages and I'm not going to rush into reconfiguring the whole caper. Will happen if need be but playing around with the controller settings and rear suspension, not to mention my riding style will come first!!
Cheers mate and did you see the vide, it's a bit poor but ok
 
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