Light weight full suspension mountainbike --WITH VIDEO--

Discussions related to motors other than hub motors.
This includes R/C motors, botttom bracket, roller and geared drives.
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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Jul 30, 2016 8:00 pm

Four 6s nanotech 8ah packs for a total of 12s-16ah.
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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Jul 30, 2016 8:22 pm

For those just tuning in, go back to page #1 to see progress photos.

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Re: Light weight full suspension mountainbike build (finally

Post by nutnspecial » Jul 31, 2016 5:43 am

recumpence wrote: The bike is extremely light for what it is. I have not weighed it yet because the packs are not installed. But it sure is easy to lift. Also, these are NOT the cranks the bike will use. I am waiting on custom sprockets from Rebel Gears for my freewheeling cranks. Remember, this bike is being built to be easily converted to crank drive. The chain management for left side drive was extremely complicated. So, I wanted to set it up this way first. The chain idler wheels are modified skate-board wheels. I have found these wheels perfect for this application.

Matt
That will be so much fun to ride!! 8)
(I tried to quote the full post, but pictures didn't convey)

I have a few constructive criticisms and questions tho.
Power: 48v and 280peak and '??' continuous? 120a? Surely you're not going with more than 4kw on the small chain and very light wheel? Not that I don't think 4kw is enough- you are in the weight range of just a typical DH bike!

The experience with my offroad build would lead me to:
-spend a little more weight on the rear wheel and drivetrain
-extend swing arm and fit drive under swingarm @ pivot
-don't run a chain and disc brake side by side
-make pack swappable

I run both chains on right side and there's still enough room for a 2.4" tire, with minimal routing of chains, even in the tight mantra urt. Alot of that is because of going parallel, and motor on swingarm. Imo no power acting on susp is also prob best. The #35 driveline is showing high wear in under 2k mi, and has needed frequent oiling with often wet and muddy/dirty conditions.

The san andreas susp looks similar to this build I will complete someday.
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I've held off because my fab skills on AL just aren't advanced enough to do a clean all AL d/o extension. (and money, and time to complete). However, it's not a bad frame and can be easily obtained inexpensively. It's 7005. You (or someone) could make a few for members, though I would try for the suggestions above. As I think you have ommited also, for multiple bikes /resale I wouldn't freewheel the motor as the white HD and necessary hub customization would be hard to make it's own worth monetarily.

Keep up the awesome work! :D

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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Jul 31, 2016 6:31 am

Thanks for the comments. I know there are concerns about component selection and power handling. Here is some info regarding the issues you raised;

I have run 40,000 watts (yes you heard correctly) (three motors) on this same style heavy duty bmx chain with left side drive (disc and sprocket on the same side) without any issues. Also, more torque is put through spokes by way of a disc brake than the drive system typically. I've built a dozen bikes this way without any strength issues at all. Also, the disc brake flange on the left side of the wheel is far stronger than the freewheel on the right side.

On the matter of chain wear, drive system components must be properly chosen for their purpose and properly sized per their torque loading, operating speed, efficiency, etc. A roller chain is suited to high torque and relatively low rpm. A toothed belt is better suited to high rpm. Now, another principal regarding this is surface speed versus power. If you have a given amount of power (watts) in a system a and you increase the speed of any given component within that fixed power system, you reduce torque (static pressure) on that component. You will notice the rear sprocket on my bike is large (60 tooth in this case). That increases chain speed and reduces torque from the sprocket teeth. It also spreads the torque loading over a higher number of teeth. This moves the high torque loading from the sprockets to the hub. This increased chain speed is not high enough to exceed the efficient operating speed of the chain. Basically, everything in the driveline of all of the systems I build is maximized and properly balanced to deliver high power with high reliability and very low wear. I have never worn out a chain or sprocket over thousands of miles on my bikes.

The pack is easily swappable. The range should be around 18 miles or so without pedaling. That should be good enough for my application. But, a second pack to swap in would be great.

Matt
Last edited by recumpence on Jul 31, 2016 9:02 am, edited 2 times in total.
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Re: Light weight full suspension mountainbike build (finally

Post by nutnspecial » Jul 31, 2016 8:47 am

All good info, thankyou! I might definitely want to try a chain like that, where do you source them and the sprockets?

Also what final reduction (tooth count front and rear) are you running, what top speed is it geared for, and is 280 the phase or battery amps?

Most importantly (I think) do you reign in the torque so the bike doesn't get ripped out of your hands? I run just speed throttle on 6kw geared for 30mph, and it's a handful, and it's hard on my heavier drivetrain.

One other thing about going right side drive, if you can input power to freewheel threads on FW hub (this is my current setup, with a white HD for the motor) it should be comparable in strength although the rotor mount does rely on the 6bolts and their tightness and sheer strength alone. There's also the dual disc hubs for right side input, I might try sometime.

Again, nice job, and thankyou!!

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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Jul 31, 2016 10:17 am

The drive side chain is a simple BMX bicycle chain. For extremely high power systems (20kw or more) a trials bike chain is best. But, for this application, a normal BMX (single speed) bicycle chain works great.

280 amps is the peak battery amps the controller is programmed for. With the weight and layout of this bike, I would need to lean over the bars to see more than 200 amps and, even then, it would be a mere fraction of a second until the front end leaps up and the throttle is lowered to keep from flipping over.

The drive system is 6 to 1 ratio from the motor to the jackshaft. The output freewheel on the drive unit is 16 tooth (White Industries) and the rear sprocket is 60 tooth. This should give me a 30mph top speed.

Limiting torque is handled two ways on this bike;

First, the controller is programmed with low throttle response. This effectively gives a throttle ramp up delay, thus softening the throttle "Hit".
Second, there is an adjustable mechanical torque limiter (slipper clutch) inside the large belt pulley on the drive unit. This will be adjusted to slip a small amount under only the harshest conditions. This will protect the driveline.


Setting up a bike with these high output and light weight RC systems is like setting up a Formula-1 car or a factory two stroke dirt bike, if setup right it will run reliably with plenty of power. However, if setup incorrectly, problems will occur.

My black street bike is setup with this same drive unit, same motor, same controller. It runs wonderfully with hundreds of miles problem free. That bike is geard for 37mph and weighs 90 pounds (LOTS of lipo). This bike should be even more reliable because of the lighter weight and lower gearing. That is the hope, anyway. :mrgreen:

Oh, my black street bike is running a CA (setup for RC use). This bike will not have the CA for a few reasons;

#1 Complexity. I want this bike as simple as possible.
#2 Throttle response. The CA tends to dampen the throttle response and that affects the "Feel" of the bike. My Motoped had a direct PWM throttle like this new bike will be wetup with (no CA) and I prefered that setup for dirt use. For street use, I prefer the CA.
#3 Ease of build.
#4 Removeability. I want to be able to completely remove all electric components on this bike as quickly as possible so I can transport it on a bike rack on the rear of my car without worrying about rain. I plan on making the entire electric system removeable in less than 10 minutes for easy transport. The CA would increase removal time.
#5 Stealth. I want fewer components on the bars so it looks more like a normal bike (not like the drive unit is not visible :mrgreen: ).
#6 Distractions. On a long range street bike, I like being able to monitor amps, volts, battery state of charge, etc. But, on a dirt bike or trail bike, I prefer no distractions to take my eyes off the trail.

I may go with a CA eventually if I find I need it for some reason. But, I would rather go with a smaller motor to reduce power and wheelie tendency (and save weight) than resort to a CA to limit power on this particular build.

Matt
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Re: Light weight full suspension mountainbike build (finally

Post by StinkyGoalieGuy » Aug 01, 2016 2:54 am

Matt,

1) Which Astro motor did you end up going with?
2) What's the steepest dirt hill you have around that you can test this on? I'm interested what kind of start from 0, low speed climbing you can get with a single speed and monstrous power.

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Re: Light weight full suspension mountainbike build (finally

Post by nutnspecial » Aug 01, 2016 6:20 am

VERY nice setup, I see how you can run the more efficient chain now. The slipper clutch and controller throttle setting capability must really help. Freewheel also is strongest where you have it. Dude that will be so much fun to ride- so much power-to-weight! Hold on!!! 8)

As a sidenote, I've occastionally thought it would be nice to have a similar clutch to other cycles (oil bath). Guess that's not something that's happening any time soon though? I guess a slipper clutch is the next best thing, if not better for several reasons/instances.

I'm guessing yours must be something between this:
zx11- https://www.youtube.com/watch?v=IFi3bKKioTQ
And this: rc- https://www.youtube.com/watch?v=3zkukUDt73s

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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Aug 01, 2016 4:27 pm

StinkyGoalieGuy wrote:Matt,

1) Which Astro motor did you end up going with?
2) What's the steepest dirt hill you have around that you can test this on? I'm interested what kind of start from 0, low speed climbing you can get with a single speed and monstrous power.
I am using a 3 turn motor. That makes around 10,000 RPM with this battery voltage. Good question about starting on a steep hill from a dead stop. As we all know these sensorless motors and RC controllers start up with a little bit of a stutter when they are under load. I don't start from a dead stop when aimed up hill. I would always give one pedal stroke then hit the throttle. On a flat surface, these systems start up just fine. However, even then it is best to give one pedal stroke then hit the throttle. It is much easier on the controller that way.
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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Aug 04, 2016 1:42 pm

The bike is almost finished. It looks phenomenal! Lots and lots and lots of fabrication was required to build this bike. But it is well integrated and all coming together. I hope to have some pictures for you within the next couple days.

Matt
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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Aug 04, 2016 5:24 pm

The bike is 95% mechanically finished.

It rides fantastic! I have only done pedal riding. But, it is extremely stable, and the suspension is perfect for my intended use. It rides almost exactly like the Motoped from a cornering perspective. The riding position and seat to bar relationship is very similar. This bike will be geared about 20% lower than the Motoped and weigh about 60% less. That should make this bike (one motor as opposed to the twin motors in my Motoped) ride nearly identically to the Motoped. We shall see. :D

The list of custom and modified parts is very extensive. But, here is a short list;

Extreme frame modifications (too many to list)
Chain management and all rollers
Freewheeling crank setup (sprocket and spacer). This is a Rebel Gears sprocket with a custom spacer on a double bearing WI freewheel (expensive)
Rear caliper mount
New rear shock and all mounts for it TIG welded to the frame to increase travel

There are many individual parts required for each item listed above. I have about 35 hours in the bike so far (and thousands of dollars).

All that is left to do is fabricate a left side chain guard, mount the controller, and do the wiring. I figure there is about 6 hours of labor left to get it going.

Matt

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Re: Light weight full suspension mountainbike build (finally

Post by waynebergman » Aug 04, 2016 6:25 pm

Wow that is super nice Matt. Hope you get lots of fun out of this bike.

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Re: Light weight full suspension mountainbike build (finally

Post by Kepler » Aug 05, 2016 3:37 am

beautiful work Matt. Class leading build as always. Hopefully we can see a bit of video of the bike in action. Do you plan to singletrack the bike or mainly use it for on road duties?
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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Aug 05, 2016 6:56 am

Mostly off road. I think single track would be better with right side crank drive. We have very little single track around here. I will take it everywhere I can to see how it performs, however.

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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Aug 06, 2016 11:49 am

I have it running! I will post pics and video later. Here is the skinny;

It has absolutely, positively TOOOO much power! The data logger shows I have only pulled 7,900 watts. But, this thing is a friggin MONSTER! Geeze, one motor...... So, I turned the throttle end point down (simple potentiometer) to 60% and it is a joy to ride. The bike handles wonderfully and is just pleasant with enough power (at 60% end point) to lift the front wheel without a problem. I will have to weigh it. But, it is really light. It feels like a typical mountain bike, more-so than any E-bike I have personally ridden.

The trail manners are awesome as well.

Don't tell my wife, but, I flipped the bike already (bent the cranks). It is soooo powerful at full throttle. That is what prompted me to turn the end point down. I think it would be perfect with a 3210. I may, indeed, go that route. It would save weight too.

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Re: Light weight full suspension mountainbike build (finally

Post by Thud » Aug 06, 2016 2:46 pm

Gorgeous as always Matt....but you need to take 5 minutes & program your camera.....or is it really Jan. 6th 2003?.
:mrgreen:
get some......

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Re: Light weight full suspension mountainbike build (finally

Post by nutnspecial » Aug 06, 2016 2:50 pm

Yes, control is the b1tch of it lol. Could you rig a 3 speed switch? Even when it doesn't take down the amps it's helpful to dial in the speed throttles to a lower speed limit (which I think you've done there?). It's really useful for control (so you don't put yourself thru a tree or take flight), but I could handle alot more KW than I have when in the wide open (bike, motor, and drivetrain probably couldn't though). Toolman's bike comes to mind, I wonder what type of motor control he uses?

Glad you got it running nice Matt, I bet a bit more riding and you'll become more used to the power/weight ratio . . . 8)

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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Aug 06, 2016 4:59 pm

I have been trying various setups looking for the ideal performance versus controllability. The bike was built with a 3 turn 3220 at first. That is too much power (though admittedly it is fine with the throttle end point turned down a bit to soften the output). Then I tried a 6 turn 3220 (1/2 the RPM) and geared it up to a similar top speed. This cut the torque way down. But, the torque was cut too far. It ran like a pooch. I think a 4 turn 3220 would be great or a 6 turn 3215. I may move to a 6 turn 3215 and do some testing. But, for now, I am going back up to the 3 turn 3220 with throttle end point adjustment and I will be extra careful with it.

Beyond that, the only issue so far is a tensioner spring that is not strong enough. Under heavy stutter bumps the power chain can derail. I ran a stiffer spring and that nearly eliminated it. I need to go even stiffer and that should solve it.

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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Aug 06, 2016 7:04 pm

I went back to the 3 turn 3220 and have been riding it alot. It looks like the range at 25mph is around 20 miles without any pedaling. That is right in line with my black bike (around 33 to 36wh per mile). Bear in mind, I have done zero hyper-miling on this bike. It is just ripped on. :mrgreen: So, that range is really great from my perspective.

The complete bike weighs in at 54 pounds. Bear in mind, that is WITH the pack. This is not a back-pack battery bike. The pack is inside the frame. That is a touch heavier than I was trying for. It also has more motor and more battery than it really needs. I could easily shave 6 pounds off the bike by reducing pack capacity and running a smaller motor. But, I like the pack capacity I have. If I pedal on the flats I could increase my range 10 miles easily. Oh, that brings me to the next point; This is a truly great pedal bike as well. In fact, it is a great hybrid. It pedals just fine and the electric drive is well integrated into the bike. It is a joy to ride by adding pedal input and/or motor input as I see fit. Just wonderful to have an E-bike that is still a functional bike.

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Re: Light weight full suspension mountainbike build (finally

Post by ferret » Aug 07, 2016 3:47 am

Hi Matt.
Why are you using a freewheeling carankset with a left hand electric drive?

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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Aug 07, 2016 6:05 am

The main reason for the freewheeling crank is because I want to try this bike with crank drive too. I wnat it to be convertible from left side drive to right side drive relatively easily.

Beyond that, I like freewheeling cranks. I back spin my cranks periodically and the freewheeling cranks have a better feel to them when doing that. :D

I could shave some weight off with standard cranks, though. I may go that route just for weight savings at some point.

On the subject of weight, I have been messing around with weight and I have found that for high power and high speed, a bit of added weight adds stability and a solid feel to a bike. So, reducing weight too far may be detrimental to the handling of this bike. One other item I want to mention is the anti-squat layout of the rear suspension (swing arm pivot above the drive chain). I really like the way the bike responds to throttle input with this setup. The rear end stays nice and level when feeding in throttle, rather than squating like other bikes I have ridden. This anti-squat geometry makes chain management a bit more difficult, but the ride quality seems to more than offset that.

Also, I GPS tested the bike. On a full charge it runs 34mph. That is too fast for this application. Ultimately it should be nor more than 30mph (actually 28 feels like an ideal top speed for this bike).

Matt
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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Aug 07, 2016 11:55 am

More testing and validating. After a long ride I am happy to report the wh per mile is 25.5 at 20mph! That is over 23 miles of range from my 12S-16ah pack. That is considerably better than I anticipated.

The wiring is completed and all adjustments have been made. I hope to shoot some video within the next few days.

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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Aug 07, 2016 3:17 pm

Well, I took the bike for the first long distance ride out of town. It was a bit of a leap of faith on such a young project bike. But, I have gotten to know these systems pretty well at this point. So, I figured I would give it a shot.

The ride consisted of 15 miles of mildly hilly terrain. I had the top speed set for 20mph. I pedalled along on this ride enough to make me sweat a bit without making my legs burn (I rode 17 miles on my pedal bike with my son yesterday and my legs are sore). I cannot wait to see the WH I used when it recharges.

I have to say, this bike is the perfect hybrid trail bike for my area. It is more than fast enough for anything I could ever want to do with it and it makes such a perfect bike to pedal 1/2 of the time and hit the throttle the other half of the time.

I would say the only things I do not like about the bike are related to the push for light weight. The forks have a bit of flex (single crown forks normally do), the wheels have some flex (again, light weight), and the seat. I have a cushy seat for it that is shown in the early pictures. But, for the sake of weight and looks as well as pedalling out of the saddle, I went with a relatively thin seat.

Beyond those items, the bike is awesome. Heck, even the things I mentioned are not a big deal. Just worth noting so you guys do not think I am too terribly biased about my pet project. :wink: (Of course I am biased just as a parent is biased of their child). :mrgreen:

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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Aug 07, 2016 4:55 pm

More pics. :mrgreen:

In these pictures you can see the handlebar arrangement. I prefer using a twist grip shifter mounted on the left bar when using a twist throttle. This allows a much cleaner control center for the rider and reduces the amount of work being done with the right hand.

You can see the controller and the throttle PWM interface box mounted on top of the frame.

The left side chain guard is finished as well. This is made of 3mm thick carbon fiber and is held in place with titanium nuts. I have MANY titanium screws and nuts on this bike. In fact, nearly every nut and bolt is made of Ti. I think there may be 4 or 5 that are hardened steel. The rest are titanium.

After the recharge from my last ride, the bike used 17.6 wh per mile with some pedal assistance at 20mph! That means, assuming I am willing to put in some moest pedalling, this pack is good for over 33 miles (or 23 miles without any pedal assistance at all). :D

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Re: Light weight full suspension mountainbike build (finally

Post by jk1 » Aug 07, 2016 8:09 pm

Wow awesome build.

How do you get the left side drive sprocket to fit on the left side ? Most bikes i have seen their is no room between the brake disc and spokes to add a chainring?

Also do u have a freewheel in their ? or does the LEFT side chain always turn when the bike is moving ?


Also what is the full throttle no load current of the motor and drive system with the back wheel off the ground ? compared to just the motor full throttle no load. i.e just wondering how much the drive system ads to the losses as it seems to be efficient.

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