Klein Mantra Meets BHT!

[nutnspecial]

I'll try to keep a current-ish vid or two of the bike up here on top.

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Thanks to all the members, moderators and gurus, and of course admin!!
And here's a bit of a parts list I've started for tracking products/prices/opinion on my choices. . .
http://endless-sphere.com/forums/viewtopic.php?f=3&t=69503
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What you're looking at is my xc klein mantra. It is now 65lbs w/5.8ah battery. 84v lipo, ~60/160a current. I've retained 7 gears (11-36:48) and added a freewheeling bht motor. I regularly get 10miles from one 5.8 pack, and can scrimp 15mi @25-30mph pedalling. It's geared down for max torque and the max speed of 40mph. I may still gear down 10% to save some current draw while keeping the torque.




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Here's my little story
I saw a boosted board a few months ago (feb2015) and got the bug. Upon finding the sphere I realized I could do something similar to my trusty mountain bike. I don't ride it hardly at all anymore because it seems like all work and no adrenaline. It's the damn sportbike in conjunction with less convenient access to where I prefer to ride- the woods. I want to ride more, but to be able to strongly suppliment the ride for more distance, speed, and fun! I wanted to put gravity on my terms so-to-speak.

A few build restrictions- I don't have a tig or much aluminum experience, so I refused permanent mods to the light and artful mantra comp frame. I wanted to keep it as light as possible, but as powerful also for around 35mph topspeed.
Best weight, power, and handling bolted on.

After countless hours looking at other builds denoted as dd, geared, and middrive, I ended up seeing a BHT build. Although the founders apparently were doing this directdrive style years ago, I think it needs it's own category and name. Perhaps middirectdrive? This would allow newcomers easier access to info on the style, and it seems to be gaining momentum particularly with the bht motors.

The BHT specific middirectdrive builds that showed me what was possible are by Evolutiongts, Drum, Skeetab, Jackjetful.

The benefits over hubs or middrives build are:

1) You can gear and volt your bike however you want. I'm using 18s and 11/50t reduction to a 26 wheel for 35+ on flat/40mph with pedalling. 75a of torque is quite alot when applied 0-35. You could also gear much higher and I think it would compete with mxus in high speed performance.

2) NO cogging! whiteind hd freewheel and an adapter are allowing complete freewheel and pedal/freehub isolation.

3) Centered and sprung motor weight in frame for best handling, while the independant drive isn't held back by bike gear weakness such as a middrive.

Downsides I can see have got to be mechanical fitment, and probably more weight than just a middrive.

My build features a custom adapter (vid below) made with a grinder, drill, and wire welder that allows a stock xt hub to accept the white hd fw and then a fh body/cassette both on the right side. I currently use 4 gears on my freehub for pedals: 36, 28, 15, 11 :48. If your frame is wide enough, you can run all the gears on a cassette, which I might prefer- along with also losing some weight on the build if possible. This will defintely require a custom swingarm, probably close to 150mm, depending on chainlines, wheel dish, and hub/fw.

Some other custom stuff on this build is a steel swingarm/triangle extension that bolts to the original in 4 places- no new holes in the old frame. It moves rear wheel back about 4.5" and widens to 142mm.
The bht was also customized to simply bolt to the frame with 3 bolts and one mount. My first overcomplicated attempt had movement under torque even with 4 bolts and both orignal mounts.

It's currently drawing about 5-6kw max and weighs 65lbs w/ 5.8ah batt.
More than I could have hoped for in performance.

Control : I use a halftwist and 3speed switch for infineon @ 50% 75% 100% for added safety and control. With present gearing and 20s, 1' is great for very controlled power at very low speed, while 2' gives up to around 30mph which is perfect for my top pedal ratio @speed thus helping battery usage on average to 3mi/ah with peddling.
3' is all out and can be used from a stop, but it is not for beginners, let me tell you! The only use I can see for this is fairly extreme admittedly with this gearing, and the low speed high torque stuff (1st vid next page)in abundance does tend to be harder on the motor. But that's the point, I can gear it down a bit, or limit some amps!

While the switch doesn't limit power, limiting the motor rpm is still helpful when the motor can spin up very fast lol.

This is me testing spd 3, need to pay attention and be careful, it's touchier than any dirtbike or sportbike I've ridden. I'm workin on a better camera and mount, so hopefully more to come.
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This is a little explanation and breakdown of the dual fw. It's a sht vid, let me know if you need better explanation.
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Here's a few early pictures too

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[izeman]

cool. i like it. and a brilliant idea for the chain from motor to rear gears
my mantra looks so completley different ...

 

[nutnspecial]

I can't think of a more appropriate person to comment (and first)!!

Your build was one of the first I read, idealy remaking the rear stays would allow for so many things. That route was out of reach for me though, at least for now.
If you like middrive, you're sure to like this! Maybe think about it for the next one?
I'm real happy with the mantra- great strong/light bikes, and I like the high pivot design- unique for sure. If I ever do another bike it'll either be a mongoose cx variant or from scratch, and that would probably be for a dirtbike style.

I will add some vid on how I did the dual freewheels and a little on the bike mid-build.

Thanks izeman,

jay

 

[beast775]

Excellent freewheel build,i like the bike.hope the freewheel lasts :wink: ..

 

[madin88]

nice conversion. i like the design of the klein frame with its unsual but well made suspension.
izeman, on your custom swingarm there would be enough space for a BHT

 

[izeman]

Thought the same. But to be honest don't want to invest any more time into that build. It's working fine from a technical standpoint but to be honest the big battery and the small tires make it a quite strange ride - at least compared to my kona mid drive.

 

[nutnspecial]

Thanks maddin and beast! So far- so good! eventually I'll do some more coverage. . .

It would be a whole new build for izeman -wider bb and back to big wheels, rework swingarm and susp.
But consider it if you get too bored :wink: !

 

[izeman]

i'm just building a new mid drive. so i'm already busy working
i'm glad of all finished projects. but adding a 10kw motor to the mantra would for sure be super coool!

 

[nutnspecial]

but adding a 10kw motor to the mantra would for sure be super coool!

And I thought I was the crazy one! 5-6k is mooore than enough 4 me (about to try 82v 75a), especially geared for 0-40mph. Would be interested to see geared up to 60+ though...but It won't be me lol.

 

[duffmanaudio]

Nice build. I'm considering using this motor. What type of chain is the sprocket & what controller are you using? Also where in pa are you from?

 

[Voltron]

Two nice looking builds going two different paths. Sooo not trying to be jinxer....but the Mantra was built (most of them almost twenty years ago) as a very light weight race bike with a limited usable lifespan. Several of them sheared off the entire headtube, separating completely from the rest of the frame. So really be looking out for cracks given the new loads on the frame from the weight and speed....

 

[John Bozi]

cool work,

I have thought about bht for a while now but I just can't work out my swing arm, if I go steel does the back end up being the same weight as a hub motor? What hub to run for high power?

 

[nutnspecial]

Yo guys-

Duffman, I'm in central Pa, I worked around reading for a couple years though. Maybe we could end up riding somewhere half way! I don't know any other e-mtn bikers.
I used #35- cheap and plenty strong, and not too big for 2500rpms @ motor. original motor sprocket is an 8t #40, and the shaft diameter is an odd size. I ordered the #35 front sprocket from amazon for 10$ with id of .625", then slightly enlarged it with a die grinder to slip over larger diameter part of motorshaft that's closer to the motor. Instead of bothering with a machine shop for keyways, I welded the sprocket to the shaft, in a way that It can removed without hurting the shaft. The rear sprocket can be bought in aluminum as blanks in 1t increments. I think it was about 35$ from a kart place.
#219 is the other popular kid on the block, and is almost as strong and supports faster rpms, but is more expensive and not as easily obtainable, same as the sprockets for it.
My controller is 18fet 60a 90v program infineon from em3ev. Set to 67a/200ph and hitting 75a draw, it doesn't even get warm. I'd be curious to see the programability on similar controllers, as more is better. (unless you use the ca to control, or get an adaptto)

Voltron, thanks for the reminder. I think knowing one's equipment and being observant is right up there with 'look both ways b4 crossing street'.
I didn't get a single hit on the net for frame fails, so if you have any info to back that up, I want to hear it!
Not only do klein's designs have no more of an expiration date than other aluminum frames, the level of design and quality was paramount for these bikes.
As aluminum ages, it gets harder/stronger, but eventually this hardness leads to any microscopic fissures/defects slowly growing.
Any aluminum bike should be watched as it ages, but most failure prone are bikes that used inferior and poorly checked material, and klein is touted as the best, meaning it stands to last the longest imo.
Hopefully you're not just flamin- as I said, thankyou, but i need to see some more info on 'limited usable lifespan' before I'm convinced. I did find this though. . . .


Hey John, you have done alot on the sphere. Thankyou! Love your vids and build! I got into this for the exact reasons as you: supplement the normal mtnbike riding with power so as to put gravity on my terms lol. Bike weight is a big consideration though. I think for weight (even with a steel frame add-on) this is still far better balanced & prob lighter than a rear hub, and doesn't weigh much more than just a middrive. The bracket weighs under 5lbs, and covers 75% of the top of the triangle, so not an issue for me- a 'necessary' evil to lengthen wheelbase just to fit the bht back there. I scrapped the front deraileur, but the current 48: 11, 18, 28, 36 give me excellent pedal range. And 60lbs w/o battery is still pretty light and balanced.
You could run any hub you want, mine is xt, I simply got a longer solid axle for the 142mm d/o. Watch the 3rd video from top if you havent, that may help explain my method for fw'ing- I can use any hub that accepts a freewheelbody. But much easier would be skeetab and drum's approach, just bolt the sprocket to the hub. Stevil may have another set of those dual disc hubs/wheels, but my concern with this is they are too wide to ad anything but one bike gear. Let me know how else I can help!
You already have a white hd mounted back there? so workon mounting the bht and try it first, then do the pedals. My adapter can solve that, or there's lmx 2 or jackjetful that have motor gears and pedals. Many ways to skin the cat, but the bht begs to have the bike build around it.
Is there room for it on your bike? If not, what about skeetab's approach, buy a walmart genesis and put it on that to see if it's better than your current setup? I really think you'll love it, and know you'd give it proper video and coverage!

 

[Voltron]

Def. not singling out Klein...the same concerns are there with any 90's light weight race bike...

 

[Voltron]

Like I said..not trying to jinx anybody.

 

[nutnspecial]

Ouch but thanks. The rear triangle actually is getting more of my attention because of torque and geom mods.

That break appears to be direct shear forces down on the seat and/or up on the rear wheel, past the shock bottoming out. Like a heavy rider doing a huge drop.
I've been fairly considerate of the physics of this in my mods, susp, and power application, and in addition since me and the bike are about 225lbs, I'm expecting the extra forces will not exceed a 30-50lb heavier rider on the original bike, crashing excluded. The biggest thing really is lengthening this triangle, which will put more force just where that one failed.

If you come across any other failures let me know, I didn't find any mantra failures at all.

 

[Voltron]

I think the red one IS a Mantra? Here's another one with a crack starting in the same place..

 

[Voltron]

Again, totally not bashing Kleins, but as masterful an example of thin wall aluminum welding/rolling piece of art as they are, it's just the nature of the material. Very thin stiff aluminum subjected to cyclic loads cracks over time...and even the best of engineering can delay it only but so long, and visual inspection can't always warn you with the appearance of cracks that a brittle section is about to bust right open. Not down on your builds of course!

 

[nutnspecial]

totally not bashing Kleins

Well I should hope not . .. . . and you WOULDNT DARE lol.

Surprisingly those two mantra failures are on one of the thickest areas on the bike, but it's because it carries the entire weight of the rear. Easy to fix or beef up, and not as catastrophic as headtube failure that you originally were concerned about.
Prone to failure if grossly overloaded past a bottom-out of rear susp. But not speed or power alone imo.

Thanks for the compliment on my build. (the other one is Izeman, he's had his for as long as me, but electrified it years ago.)

I really like mine, and I'm not going to be doing mountain dew commercials, so I expect it to last.

Thanks also for pointing out potential flaws and for finding those pix!

 

[izeman]

I built the rear frame by myself. it's made of steel. but not because i was concerned about strenght but because i integrated massive dropouts for the motor and i wanted to make a longer wheelbase.

 

[Voltron]

That seems like a good idea Izeman. It looks like you kept the design of the better one of the stock rears, where the pivot is right at the apex of the triangle and not on an extension of the triangle.

 

[Voltron]

I know you're over hearing about it, but for anybody else still thinking it's a good idea.. this is a quote from somebody with a different Mantra that snapped.

"I was coming to the top of a climb, seated, and I felt the rear sag unexpectedly. No warning creaks at all, just sudden complete failure. At first I thought the shock had blown.

Keep in mind that I also regularly inspect the rear triangle for stress cracks since I know it's a common issue."

 

[nutnspecial]

EDIT- I'd like to interject here that there is a previous post from voltron missing

"Voltron":If you look at Izemans, you can see it has a slightly different rear triangle. I don't know if they changed them because of cracking, or they're different for smaller vs larger frames, but both the cracked ones in the pics are your style

as well as my reply of

"omg dude, give it a rest".

These were chronologically before the post where he has run out of pictures on the internet and is now apparently quoting stories. Did it appear I wasn't getting the point?
So that's the missing bits and some context for the conclusion. Maybe I should have spent more effort being diplomatic, but if I think someone is looking for a reaction . . .
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Voltron, this is past my line and I'm gonna kindly invite you to get the hell off my thread-

This thread is for people to see and ask about my build. A comment or two off-topic is okay, and I welcome some pointers; I do believe I've given you that, but this is too much man.

GO START YOUR OWN THREAD TO WARN EVERYBODY ABOUT THE MANTRA FRAME, OR WHATEVER ELSE YOU DESIRE; take an ad out in the newspaper, run a commercial, drop pamphlets from planes, skywriting, singing telegrams- I don't care.

But for sake of all that is holy, stop doing it here!

 

[mikebikerad]

I had a crack form in the same place as above. Was running a 48 volt 20 ah ping split pack on top and bottom of main tube. It was much more clumsy then your setup.

 

[Voltron]

I guess when you said let you know about some other failures because you hadn't heard of any I thought you were serious...my bad.