LMX P2 : Freeride trials motorcycle frame development

[efMX Trials Electric Freeride]

if you were to overlay these two bike images i think you would find the lmx bb is a bit rearward relative to the seat compared to dh & freeride bikes.. lets see the geometry spec of that bike

I would not care too much about the position of the BB. If you want to use the bike as a commuter bike this might be a problem. But the intended use of this bike is freeriding. And while freeriding, most of the time you are standing on the pedals. The only purpose of the seat is not to sit and relax but to bring some pressure on the wheels when cornering. And the closer it is positioned to the handle bar the more weight ist transferred to the front wheel. (Same reason why you sit almost on the tank when cornering with a MX bike).

Check the position of the BB on a normal DH bike:

It is also behind the seat and I guess it is meant to be like this and not a design failure

one can see from the new pics that indeed the cranks are currently behind the seat..
that would not be ideal for pedal input (but i expect it will be corrected before production)..

Looking at the picture now, the motor should be at the back and the crank shaft in front of the motor. Its hard to judge by the picture but it looks like you have to move the seat quite a bit back if you want to have a normal position. Anyway, I really hope that this is not the case! We need to see the frames profile to be sure.

 

[Allex]

if you were to overlay these two bike images i think you would find the lmx bb is a bit rearward relative to the seat compared to dh & freeride bikes.. lets see the geometry spec of that bike

Yes you may be right. I believe that you still want to have a bicycle like angle for the pedals, not because of the pedalling but just to have a natural support for the legs. It would feel ackward to have the support to far away at the back. This will make you body want move back, away from the seat all the time. Of course you could fix this by moving the seat back by 10cm but in this case you would be sitting to far away from the handlebars?

 

[efMX Trials Electric Freeride]

i agree, top tube length likely will need adjustment as well..
bike geometry is not the place to go experimenting imo..
just copy the geometry of current dh & freeride bikes on market..

if you were to overlay these two bike images i think you would find the lmx bb is a bit rearward relative to the seat compared to dh & freeride bikes.. lets see the geometry spec of that bike

Yes you may be right. I believe that you still want to have a bicycle like angle for the pedals, not because of the pedaling but just to have a natural support for the legs. It would feel awkward to have the support to far away at the back. Of course you could fix this by moving the seat back by 10cm but in this case you would be sitting to far away from the handlebars?

 

[louis raaijmakers]

the bike looks great so far!
but i have the same concern as every one else. but you will fix it :wink:

succes with you bike's
louis

 

[gensem]

Looking good... Im still not sure if im going to use regular dh frame with a bicycle chain and cassete or this frame with a kart or motocycle chain.

 

[bzhwindtalker]

 

[brooklands]

Could you describe your first impressions pleeeeeeaaaaassssssse . And we need vids...

 

[wildharemtbkr]

Love it! How much does it weigh? Complete, and frame only? Does the rider have any gears? Aren't you the video king? Where are they? Anxiously waiting!

 

[madin88]

what no load rpm you have on the wheel and what reduction?
can you say something about performace compared to the 6pole 50mm stator BHT, yksuccess BIG BLOCK alternative?

 

[sigimem]

On facebook he said 28kg including battery (14s4p 18650) and motor.

 

[recumpence]

Looks very well thought out. I am impressed by the design.

Matt

 

[upek]

Design is great, but battery box is tiny. I would like to have at least 100 cells (18650)

 

[Allex]

Battery box is actually quite big. I think you can fit 100pcs of 18650

 

[bzhwindtalker]

Design is great, but battery box is tiny. I would like to have at least 100 cells (18650)

The goal for this project was to make a very slim ebike, with good pedalling caracteristics. So we chosed to have a small battery box, perfect for the intended goal of the project.

Design is great, but battery box is tiny. I would like to have at least 100 cells (18650)

I will post the inner dimentions of the frame as soon as I have some free time, it can probably fit 1kwh in prismatic lipo cells (multistars and similar).

Looks very well thought out. I am impressed by the design.

Matt

Thanks Matt!

what no load rpm you have on the wheel and what reduction?
can you say something about performace compared to the 6pole 50mm stator BHT, yksuccess BIG BLOCK alternative?

It's closer to the GNG kit motor with about 67kv

Love it! How much does it weigh? Complete, and frame only? Does the rider have any gears? Aren't you the video king? Where are they? Anxiously waiting!

This prototype has 3 gears for the rider and a freewheel for the pedalling, the final version will probably have a standard rear fat hub with 8 gears and left side drive chain as suggested by efMX here :wink:

Videos should come soon, 1 week or so from now!

Adam

 

[sigimem]

Do you have a price already?

 

[giblet]

That's looking nice man!!

If you need test riders I'm in the UK just over the channel...

 

[efMX Trials Electric Freeride]

well as long as some of my ideas are catching on..
here are some other design concepts to maybe consider.. 8)

multiple point rear top shock mount :
having a few different top shock mount hole options allows for rider adjustable
head angle
bottom bracket height
shock length
wheel size
modular tunable geometry
~3 production geometry tune (shock mount hole) options:
xc /trial - tight geometry
freeride - slack geometry
dh / high speed - slacker geometry

seat strut :
maybe consider a four bar seat strut that would go around the shock mount..
instead of a long two bar cantilevered seat strut in front of the shock mount..
this would allow the rear shock mount to move forward / back without affecting seat strut location / angle..
also a shorter four bar seat strut would be stronger than a long cantilevered two bar strut (for the heavier riders

glad to hear about the possible switch to left hand motor drive
i think this will offer several advantages that i mentioned already..
but another potential advantage with left hand motor drive and segregation of motor / pedal chains is that :
spacial separation of drive chains motor vs crank / pedal allows for location movement of cranks/ bb as needed
unrestricted by cross chain clearance, interference, etc.. in other words the crank location could then be moved around independent of motor location..

keep up the great work!
looking forward to the videos!

 

[crossbreak]

This prototype has 3 gears for the rider and a freewheel for the pedalling, the final version will probably have a standard rear fat hub with 8 gears and left side drive chain

left side drive chain would be a step backwards IMO. With a fat hub you can have it all on the right plus 8sprockets. Fatbike hub =170mm? what about that 150mm shimano zee FH-M645 hub? you used the 142mm in your last built (as i suggested) and tried to get the power through the freewheel spline. that freewheel failed.
So what about using the right spoke flange instead to bolt on a adapter plate (using 9pcs M4 bolts for example) for the large drive sprocket? This plate would have 18 holes with larger BCD to take the spokes. this adapter could be a simple 3mm stainless sheet. laser/plasma cut

this way there would still be the space for an 8speed cassette on the freewheel spline.

I could make a CAD drawing of that hub+adapter if you like

 

[crossbreak]

9 inner holes for M4 bolts to the hub (into the right side spokes flange of the hub), 18 outer holes for the spokes. six holes at 5.25" BCD for the #219 sprocket

 

[bzhwindtalker]

Crossbreak, some insight on why we will likely make the switch to the left side :
We lack a bit of real estate and getting both chainlines to work 100% on the right side is a nightmare.
Getting custom hubs made in 50 piece batches would cost up to 100€ per hub without axles and bearings minimum even from holy china if we want to keep quality up.
The freewheels are not always up to the task either, the (cheap) flanged freewheel we use on the prototype has already engagement issues despite that we did only test with 1500w peak for now.
Also, something that we noticed while riding the bike is that the weigh of the drivetrain is desequilibrating the bike when rolling hands off the bars.
We will bundle the frame/motor kit with a small kelly, so we will be able to enable regen with some hydro e-brakes and save some pads.

About hubs options, 150mm would not work for chainline because we designed the bike around a 100mm BB so we need a 170mm rear hub. if you look at this picture of a fat bike hub :

There is not enough space to fit the cassette, the sprocket and the derailleur all on the right side. The less custom machining we have to make, the best product we can deliver for the $$$. Interchangability and reliability are also key goals for us. Also this hub would be around 35€ a piece in bulk with axles and stuff.

Natas, I think we could accheive multiple positions with some simple tricks like adjustable length and angle of the seat, and as you said different positions/lenghs for the rear schock. Using 180mm or 200mm forks could also be part of that change in geomerty. For now the bike rides very well like that, super agile and feels lighweigh.

Videos soon, we need to fix this failed freewheel.

 

[crossbreak]

if you order a custom 170 mm hub in china, you could simply use a BSA threads for an 8 speed freewheel. Guess this way you would be at way less than $50 per piece? No need for a super robust freewheel anymore as you dont need to push motor torque through that freewheel.

12mm though axle, i guess?

If there is so much real estate on the left side, do you think we can fit a 20mm wide HDT 8M belt to replace the #219 chain? I dont like the idea of a well oiled chain next to my brake disc

If you order custom hubs from china, count me in for at least one please. And show us a bit of your CAD artwork please!

 

[efMX Trials Electric Freeride]

triangulated swingarm is not compatible with belt drive

(how would you get the belt on / off??
also belt drive is not good for offroad due to belt non trail side serviceability, etc..
you can use a non wet chain lube such as chain wax, etc..

If there is so much real estate on the left side, do you think we can fit a 20mm wide HDT 8M belt to replace the #219 chain? I dont like the idea of a well oiled chain next to my brake disc

 

[Drum]

Hi Adam, I've been watching progress on this project with considerable interest.. I think you have come up with an overall concept that is close to ideal.

I would support moving the motor chain to the left and leaving the full range of pedal-powered gearing available on the right hand side. One thing to consider though: If using the same bolts to mount both the sprocket adapter and the brake disc, the "drive" would sometimes be forward (under power) and sometimes backward (under braking). If there was any play in the mounting bolts this could quickly lead to wear. The disc and adapter should be a snug fit and the bolts should have plain (not threaded) surface where they pass through the sprocket and disc. Use high quality fasteners and loctite!

With the direct single reduction from the motor to the back wheel, it is an ideal setup for using regenerative braking. However if you had to pedal home with a flat battery you would definitely want a freewheel or disconnect in the system to allow pedaling without spinning the motor.
I wonder if there is a lockable freewheel available? I have never seen one. It would be an interesting design exercise!

Seat mounting position etc can easily be modified after experience with riding the prototype.

Like so many others, I am eagerly awaiting video....

Regards,
Dave

 

[gwhy!1]

Hi Adam, I've been watching progress on this project with considerable interest.. I think you have come up with an overall concept that is close to ideal.

I totally agree.... but you now need to work out a way that only needs 1 chain to the rear wheel... anything with 2 chains to the rear not so good... 1 chain,,, even if it means 1 fixed pedal gear ( but it is possible to have 3 gears up front just off the chain ring) there are ways to do it... and i think you have the drive to get it sorted 8)

 

[crossbreak]

I think 2 chains is ideal. Mixing a reduction (motor) and overdrive (pedals) leads to complexity and additional weight we really dont want. All that just to have one less chain? I have tried multiple times and stopped

The disc and adapter should be a snug fit and the bolts should have plain (not threaded) surface where they pass through the sprocket and disc

This makes no difference if the bolt connection was planed right. The bolts shall not carry any torque/shear load. The shear load is transferred by friction between adapter and hub alone.
Instead of wasting time with trying, do a calculation according to VDI 2230. Really interesting to see what is the maximum torque for our 6-bold disc brake flange

The lockable freewheel: Miles once posted a link, that was still alive last time i saw it. Maybe i can dig it out again.

http://www.ebay.com/itm/Vintage-17T-Suntour-Single-Lockable-Fixed-Freewheel-For-Coaster-Brake-Hubs-/111616956561?pt=LH_DefaultDomain_2&hash=item19fce39891