Light weight full suspension mountainbike --WITH VIDEO--

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Light weight full suspension mountainbike --WITH VIDEO--

Post by recumpence » Jun 11, 2016 4:20 pm

Hello All,

I have been thinking about this build for a very long time. Those of you who know me know I tend toward extremely powerful bike with long range. These two traits dictate high weight and relatively bulky shape and size, even with the use of Lipo cells. However, this build is focussed in a different direction.

I decided to pull the trigger on this build at this time because I made room in the stable by selling the Motoped. I also realized I have a motor, drive unit parts, a controller, lipo packs, and misc odds and ends lying around. What I am missing are brakes, forks, and a frame. At least I WAS missing a frame until now......

This is a frame I have lusted after for a long time. I remember when this bike was released in 92. I was transfixed by it. Since then I have always wanted one. A few years ago I bought a Mountaincycle Tremor frame and loved it (my son has it now). The San Andreas frame has begun going up in value recently. So, I figured if I want one, I better get it now before the prices go up even higher. I looked for a frame that was heavily used (I did not want to alter a perfect frame), yet still looked good. This one seemed to fit the bill. I also wanted to find a bare aluminum frame. This way I could weld to the frame without having to have it bead blasted first. Oh, this bike will remaind bare aluminum, at least for the forseeable future. This is for looks and so I can weld to the frame at any time.

Here is the proposed system;

---3 turn Wye 3220. This is a motor I have here at the shop that I may use. I also have a 6 wire, 6 turn 3220 I could setup with Delta-Wye switching. Last choice would be a high RPM (probably 3 turn) 3215. This option would be chosen to save weight, add performance through running extremely high RPM, and to reduce the Q-factor (width of the drive). However, I do not own the 3215. So, that is alot of money to part with that is not needed considering the fact that I already have a coupld 3220s here.

---Edge 160 controller setup to run 280 amps peak.

---DaVinci Drive reduction unit in black (the last one I have here in stock) :mrgreen:

---Four Nano-Tech 8ah 6s packs for a 12S, 16ah pack. That will give me over 500 wh to work with. That should be good for 20 miles of street cruising, or 45 to 60 minutes of trail riding. I have these packs in stock. So, I want to go with them. They are perfect for this build.

---The packs will be mounted in an aluminum box welded into the center of the main frame spar. I will cut the spar in the center to make room for the battery box and TIG weld the box in place.


This bike is being built to be light. With this pack, I hope to keep the all-up weight below 50 pounds. My goal would be 45 pounds, but that may be unrealistic.

I want to use single crown forks with midest travel (this frame only has 4 inches of rear travel anyway). This bike is being built as a fun trail bike with light free-riding potential, not a full fledged dirtbike like the Motoped. That thing was scary powerful and weighed in at 147 pounds. 50 pounds and half the power is still more power per pound of bike. So, light though this bike will be, it will still be VERY powerful for its weight.

I am open to suggestions for forks and wheels. IK am leaning toward Crank Brothers Cobalt wheels. I have a set on my pedal only bike and love them. They are expensive, though.

Oh, I am trying to stay at a more reasonable budget for this bike too. I want to used as many used parts as I can to keep the cost within the stratusphere for a change. :mrgreen:

Excuse the poor quality pictures. I will take better pics when I get my other camera here at the house.

Matt
Attachments
MC1.jpg
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Last edited by recumpence on Aug 28, 2016 4:50 pm, edited 1 time in total.
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Re: Light weight full suspension mountainbike build (finally

Post by Wheazel » Jun 13, 2016 6:30 am

Nice build idea, will be intresting to see your approach.
Especially the comparision between tangent daves drive and your's for this type of application.

I have a question about your returning HK lipo choice.
Have you been lucky enough to avoid bad packs, or do you buy extra to have enough good ones?
My experience with hk packs over the years tells me the quality and reliability is low.
I have had packs delivered with dead cells,and I have had packs where cells randomly just goes bad.

Since i switched to 18650 cells, not one problem caused by the batteries.
But I guess a pack of high discharge 18650s would be too saggy for your 280A needs.
They would however be one way to save some extra weight over nanotechs, if you settled on less power.
Depending on how important the light weight part is :)

Good luck with this project! Looking forward to see your design choices when altering the frame!

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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Jun 16, 2016 5:47 pm

There are a few reasons for using these cells;

#1 Form factor. (they fit my frame design)
#2 C rating. I will be pulling 25C from these cells on occasion.
#3 Price (I have these packs left over from the Motoped project).

I am busy ordering parts for the bike. I am nearing completion of all of the component sourcing.

I will post pics as I have them.

Matt
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Re: Light weight full suspension mountainbike build (finally

Post by macribs » Jun 17, 2016 11:06 pm

Great choice of frame. This will be a fun read.

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Re: Light weight full suspension mountainbike build (finally

Post by Kepler » Jun 17, 2016 11:41 pm

Look forward to seeing what you come up with. Sub'd
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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Jun 18, 2016 3:48 pm

Here is the frame in my trusty frame jig I made last year for my black street bike.

You can see the black line on the right side of the frame just below the shock. This is the cut line for the new frame nose section.

The changes I plan to make to the frame are;

#1 Make a monocoque front section to hold the pack.
#2 Install a new shock that is longer for more travel. This frame has 3 inches of travel. I would love 5 inches.
#3 Lengthen the frame 2 inches to make more room for the drive system and battery pack.
#4 Raise the head tube to allow space for the longer travel fork I bought. The fork I have on order is a could inches longer than this frame was intended to use. So, the head tube needs to be raised. This will be partially handled by the increased length of the frame. Increasing the frame tube length will automatically increase the head tube height (if I want the frame spar angle to remain consistent). So, this step should be a natural progression of this entire build process.

Now I have to get busy with the Sawzall..... :mrgreen:

Oh, this frame will have a clamped on head tube just like my black frame. I love that design.

Matt
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Re: Light weight full suspension mountainbike build (finally

Post by SlowCo » Jun 18, 2016 4:39 pm

Subscribed.
Looking forward to see this project progress.

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Re: Light weight full suspension mountainbike build (finally

Post by litespeed » Jun 18, 2016 5:02 pm

This looks pretty interesting to me also.

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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Jun 28, 2016 4:24 pm

OK, I have a question for you guys;

I have two potential setups I can run on this bike;

#1 Left side drive (my typical high RPM setup with single gear ratio to the left side of the rear wheel). It would run a 3 turn wye 3220.
#2 Crank drive. This will utilize a 6 wire 6 turn 3220. I could run in wye for mild riding at normal pedal cadence, or switch to delta for high power riding using the lowest rear cog for more motorcycle like performance.

What are your thoughts? My concern with crank drive is the abuse the pedal chain and rear cogs take. I like the idea of multiple ratios and not having to run a second chain on the left side of the wheel along with the engineering challenge that setup brings. But, I like the high power reliability of that system.

Thoughts?

Matt
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Re: Light weight full suspension mountainbike build (finally

Post by SlowCo » Jun 28, 2016 5:15 pm

I would prefer #1

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Re: Light weight full suspension mountainbike build (finally

Post by motomech » Jun 28, 2016 7:16 pm

Four Nano-Tech 8ah 6s packs for a 12S, 16ah pack. That will give me over 500 wh to work with. That should be good for 20 miles of street cruising, or 45 to 60 minutes of trail riding. I have these packs in stock. So, I want to go with them. They are perfect for this build.
Going with 12S/2P allows some great bulk charging options and with 2P, a BMS is not really needed to charge. My controllers have LVC's, so I don't need a BMS for that.
Having gone thru Thunder and Hyperion 12S balance chargers, I now use the super high quality Mean Well HGL 320 series LED power supply and four Battery Medics to ck. the cells. I'm lucky enough to have 4 of the older Blue ones, as the new black ones are crap. But, Hobby King is now offering a Turnigy cell checker/balancer that is getting good reviews.
Here is a brief review of how I charge my 12S/20Ah pack:
https://endless-sphere.com/forums/viewt ... l#p1178098

I have learned that never "breaking the pack", the cells really stay in sync and balancing is seldom necessary.
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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Jun 28, 2016 8:57 pm

Yup, I use a Meanwell 1200 watt power supply set at 49.6 volts to charge. I use a watts up meter as a charge display.
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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Jul 02, 2016 3:57 pm

Progress......

I cut off the front section of the frame and fabricated the new section. This new front section is a twin spar design. However, it is not a side-by-side twin spar like a motorcycle. It is an over/under twin spar. This allowed easier access to the battery packs. It was also a touch easier to fabricate with good left/right symmetry.

I made a new head tube. It is an internally butted tube fabricated for high strength yet light weight.

The new nose section is not welded to the frame yet. I need to do some more work to it before I weld it.

Ironically this new frame spar is nearly identical in width and height to the original tube. Oh, this frame was originally designed for a 2 or 3 inch travel fork. However, I am using a 5 inch travel unit. So, I raised the head-tube to accomodate the taller fork without compromising the headtube angle. I am also using a different rear shock to increase the rear travel from the stock 3 inches to 4.5 inches. The frame length has been increased 2.5 inches to allow more clearance for the battery packs and the drive unit. The increased wheelbase should help the bike run stable at speeds higher than it was originally designed for.

I should be mounting the drive in a week or two.

Matt
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Re: Light weight full suspension mountainbike build (finally

Post by hedsik » Jul 02, 2016 8:21 pm

I love this build!

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Re: Light weight full suspension mountainbike build (finally

Post by cheekybloke » Jul 03, 2016 5:25 am

Awesome as usual mate, really hoping you put the power through the cranks on this build.
I agree the LHD is far easier and less work but using the rear cogs will be more economic with the restricted batt capacity.
PLus i want to do the same at some point.
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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Jul 03, 2016 8:50 am

I am torn between left and right side drive. Actually right side drive is easier to do (no chain routing problems). Also, it may sound counter-intuitive, but, left side drive is actually more efficient than right side drive because there are only two reduction stages with right side drive and three reduction stages with left side drive. The big thing, however, is power handling. This system has a power output potential of 14,000 watts peak. I will probably never see more than 12,000 for tiny periods. But, still, that is way more power than right side drive can cope with.

The way the bike is being built, I can easily (45 minutes or so) switch from left to right side drive configuration. I have everything on order to do both. I will test both and see how it goes.

Matt
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Re: Light weight full suspension mountainbike build (finally

Post by Brentis » Jul 03, 2016 9:12 am

I vote crank drive.
Left side may be more efficient and you have built some left drive works of art.
I'd like to see you use your engineering and artistry skills solving crank drive.
I imagine beefed up derailleur, 3 sprockets on a HD freewheel or some clutch or something else you imagine( I don't think you need the modern 9-11 spd nor can they handle the power you use).
HD chain and of course a ridiculous amount of power per usual.

You are very talented. Flex that muscle. :mrgreen:


Edit.

Great progress so far. Love the look of the frame and love the jig.

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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Jul 03, 2016 9:58 am

I am not 100% sure I like the look of the carbon side panels. I made them with some surface area to add Mountain Cycle stickers. However, I may go with a double XX shape carbon panels for better looks. We shall see.

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Re: Light weight full suspension mountainbike build (finally

Post by 2old » Jul 03, 2016 10:27 am

Beautiful work. Any thought to heat treating after welding or is it so overbuilt that this isn't a consideration?

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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Jul 03, 2016 12:56 pm

Heat treating is always one of the first questions asked when building a custom aluminum frame. If built right, it is not needed. An E-bike is already a touch heavy. So, adding a bit more weld or gussets to compensate for the lack of heat treating is not a problem.

At this point, I am leaning toward crank drive just to see how it runs. I have a 6 turn motor (low KV) that is six wire. I can set it up for wye to run at normal pedal cadence with lower power level, and switch to Delta while using only the largest rear cog for super high power running.

I think that is the best option to try right now. I have had so many requests for a crank drive system over the years that I think it is time to try. Besides, I know exactly how a left side system would run on this bike. So, I will start with crank drive and move to left side drive if I really want to unleash high power. It will not be too difficult to convert it later. I can set the torque limiter to slip before any damage is done to the chain or cassette.

Matt
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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Jul 03, 2016 2:01 pm

I have also decided to mount the motor down just in front of the bottom bracket. This will lower the CG.

Basically a crank drive system dictates a certain jackshaft location for tight packaging. This means the motor must be either tucked up under the battery pack or down just in front of the bottom bracket. I am opting for the latter.

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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Jul 23, 2016 4:53 pm

I have made some serious progress since my last post.

I apologize for the poor quality photos. This old camera sucks and my phone does not want to download.......

Anyway, you can see the frame is nearly finished. The main spars have the edges rounded with a router and a very tiny round over carbide bit. I fabricated new shock mounts to run a longer travel shock. The stock travel was 3 inches. It is nearly 4.5 inches now. This is a trail bike, not a downhill monster. So, 4.5 inches should be perfect. The frame is obviously heavier than the stock frame. But, it is still quite light (have not weighed it yet). I am very happy with how it is turning out so far. The only fabrication left is left side chain management. This will consist of several rollers, one of which will be tensioned to compensate for rear wheel travel.

I have everything in stock to complete this build. Stay tuned......

Enjoy!

Matt
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Re: Light weight full suspension mountainbike build (finally

Post by LI-ghtcycle » Jul 24, 2016 1:22 pm

Great build! I am excited to see how your crank drive set-up works out! I have always prefered the simplicity of a dual chain (one for motor one for pedals, but I can see the advantage of going through the cranks too, when you say this will be a "lower powered system" that probably still means more power than most of us "mere mortals" are putting to our E-Bikes! :wink:

I love that you are taking a great existing frame design and just tweaking it to add a battery pack and more suspension!!

I really need to make a FS bike some day, hats off!

Love the simple frame jig, looks very easy to use. 8)
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Re: Light weight full suspension mountainbike build (finally

Post by recumpence » Jul 30, 2016 7:45 pm

The bike is nearing completion. Sorry for the lack of progress reports. I have been focussing all of my spare time building rather than taking pictures. :mrgreen:

You can see the chain management I designed. The swingarm pivot is above the chain. This necessitated tucking the chain up very close to the pivot to reduce torque jacking of the rear suspension and to minimize chain growth under compression.

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.

Oh, there will be a carbon fiber left side chain guard to protect my pant leg (and toes) from the complicated chain/idler system.

I will post more pictures as I have them. I am determined to have this bike running by next weekend.

Matt
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Re: Light weight full suspension mountainbike build (finally

Post by macribs » Jul 30, 2016 7:57 pm

Really nice work there Matt, you got great fabrication skills. Stealth looking e-bike, nimble and lightweight.
What kind of pack are you cramming in there?

Look forward to see this on the scale.

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