Wow. As always ES comes through with lots of good stuff. Thanks guys!
by gwhy! » Wed Sep 19, 2012 1:53 am
Yes, should be pretty easy to do a POC with a gas bike with a hub on the front ( lots of video please, while you are getting used to it ),
I promise to get some video of the first rides. I expect I will need to apply some pilot lubricant (beer) to get the controls to make sense! I guess the handlebars will have two throttles, one clutch and a front brake plus the feet will have the rear brake and the shifter. Depending on the amount of pilot lubricant and my adaptability my video might go viral.
hjns » Wed Sep 19, 2012 3:31 am
Nice idea. I would put little less power in the front. Something like a 9C 2807 in front and a cromotor in the rear. For driving slowly and getting enough power, go for at least 18FET 4110 and preferably larger in the rear. You may end up with something like 6-8kW in the rear and 2-4kW in front
Thanks for throwing out actual numbers. I am thinking I might use a Magic Pie 3 in the front becasue I am used to those and the 3 is so very nice for running beefy phase wires. I am running my kid's bike at about 3 kw right now with no issues. I looked at the cromotor last night for a while and it looks promising.
by Bluefang » Wed Sep 19, 2012 6:45 am
An idea would be to use John from CRs hub in the rear. thats good for 6kw+ right out of the box and you can run a really fat 10" off road scooter tire viewtopic.php?f=31&t=40859
For the front wheel i would think a hub with a really slow wind would be a good idea as you would be best running up to 100V and the higher torque of the slow wound motor would be more useful in a large front wheel. FYI a 26" bike rim JUST fits on a 21" front motorbike hub and spoke setup so i would think you could mount a 21" motorbike rim on the spokes from a 26" hub. They did testing on 2wd motorbikes and found that the front wheel only needed a max of somthing like 20% of the rear wheels power and to make a difference it only needed 5%.
Cool ideas, but I am pretty well limited on tires. Trials tires for motorcycles are very specialized. They are super soft and we tend to run them at 4 psi. I would think that a trials tire might last for 100 miles on the pavement, that's how crazy soft they are. They are even tubeless and require a certain rim designed for tubeless. As far as I know, trials is the only offroad discipline that uses tubeless regularly. So this gives me two common options. For the rear I can use 18"X4" and the front we use 21"X2.75". Keeping in mind that motorcycles talk about rim diameter, not tire diamter, the rear is 26" and the front is 27". The only other option I can see is a 19" trials tire they make for enduro guys who ride very hardcore stuff, but I suspect it is still 26" diamter with a little less sidewall. That might be the way to go for the front as the smaller sidewall might be helpful. If I try any other tire I won't get the traction I need. If I go any smaller it will make obstacles harder to clear. This bike will never see pavement.
I was thinking Pie in front and Cromotor in rear. The Croatia folks are working on a motor that is like a bigger pie that might make a better choice for the front or even both ends. For these low speed torque situations you want large diameter motors and small diameter tires.
Cooling may be the problem, make sure to have temperature sensors in the motors.
Pie front, cromotor rear is starting to sound like a winner. If I find I am under powered or overheating I can always swap the cromotor to the front and put an EnerTrac on the rear. That would free up the pie for something stupid like the motorized, rideable, remote control beer cooler I always wanted to build.
The heat issue is an interesting one. On the one hand, we don't go fast so cooling is limited. On the other hand, trials competitions have a good percentage of time walking the sections to find the right line and waiting for your turn to ride so the duty cycle is nowhere near like commuting or something. On my third hand, during practice there can be a lot of slow speed power use without much rest. With my kid's bike we overheated at first. I put some vents in the covers and we have had no problems at all since then. I only put about half of the vents that most people do in hopes of avoiding a sctructural problem with the extra shock of trials.
by gwhy! » Wed Sep 19, 2012 9:29 am
away of controlling the 2 motors could be to use something like I have done on my bike a e-clutch lever but use the regular throttle for the rear and use the e-clutch lever for the front power, if nothing else, it will make it interesting to ride
The e-clutch lever could be an interesting option. If I want to get really silly I could think about using the throttle for both controllers but using the "clutch" to define the power split. Maybe something like out = rear only and in = front and rear 100%. But, it would probably be better to use just as a front throttle. Is this something you bought or something you made? If you bought it, can you point me at a vendor?
Speaking of that throttle, I have been thinking about dual throttles with one on each side. The transition might be easier with something to allow more "hand hanging on" like a thumb throttle or a half throttle. Maybe a half throttle on each side would allow control but also a decent grip on the bars for big obstacles. What do you think?
by hjns » Wed Sep 19, 2012 10:14 am
I would prefer one or two 3-speed switches, that allow you to use a maximum of 9 different combinations for front|rear motor speed. Having a fast (f)|fast(r) combo would be applicable only for long tarmac stretches to get the highest topspeed. A slow (s) | slow (r) combo would be practical for very technical trails. A slow (f) | fast (r) combo would be appropriate for some average riding, whereas an intermediate (f) | fast (r) combo could be used for steep hills. I don't see any uses for a fast (f) | slow (r) combo.
That sounds great. Especially during POC when I won't really know what I want until I get it. I could even change the programming on the front controller as I hone in on what works for what situations. I wonder if I can program the controllers so that speed 1 = 0% so that it could be the disconnect. Then again, it would be easy enough to hook a switch to each throttle to disable it.
It is too bad that the current version of trials rules disallow backing up. Adding in a reverse switch could really open up more possibilities that the gas boys don't get. I think I will have to do that anyway just for some fun tricks.
So, it looks like I should order me up another pie and get this party started.