Light dirt bike, QS 120 70h motor, custom steel frame

[DanGT86]

Cool project! I'm a big fan of frames with lots of steel tube fabrication. Hope the rest of the frame looks like the swingarm so far.

You could add a plate on the other side of the thin slotted motor mount area. Drill holes the same as your motor mount bolt pattern and use set-screws to set the chain tension by jacking the plate forward against the swingarm mount. This would also help to gusset the thin area you are concerned with by locking the whole motor mount flange together. Something like this:

 

[madin88]

the motor can slide forward/back to adjust chain tension. i probably have to torque those bolts really hard though to keep the motor from "creeping"

Did you do calculations for the maximum pulling force on the motor?

The controller phase amps multiplied with kT will give you max motor torque.
From the torque and sprocket radi you get the force.
On a similar setup i got 1500N on the chain but with a larger sprocket. On your setup i would guess up to 2000N, or 200kg of load.

 

[Overclocker]

Cool project! I'm a big fan of frames with lots of steel tube fabrication. Hope the rest of the frame looks like the swingarm so far.

You could add a plate on the other side of the thin slotted motor mount area. Drill holes the same as your motor mount bolt pattern and use set-screws to set the chain tension by jacking the plate forward against the swingarm mount. This would also help to gusset the thin area you are concerned with by locking the whole motor mount flange together. Something like this:
plate.png

yes will definitely do something like that at the first sign of motor "creep". but i was thinking of of welding on a piece of bar that's tapped. the set screw simply pushes on the "legs" of the motor

 

[Overclocker]

the motor can slide forward/back to adjust chain tension. i probably have to torque those bolts really hard though to keep the motor from "creeping"

Did you do calculations for the maximum pulling force on the motor?

The controller phase amps multiplied with kT will give you max motor torque.
From the torque and sprocket radi you get the force.
On a similar setup i got 1500N on the chain but with a larger sprocket. On your setup i would guess up to 2000N, or 200kg of load.

zero calculations made w/ this build (except for RPM calculations) :lol: it's all based on intuition

 

[madin88]

zero calculations made w/ this build (except for RPM calculations) :lol: it's all based on intuition

Yeah i do it the same way most of the time, but sometimes it's deeply interesting to know some values

 

[Overclocker]

zero calculations made w/ this build (except for RPM calculations) :lol: it's all based on intuition

Yeah i do it the same way most of the time, but sometimes it's deeply interesting to know some values

yeah it would be great to be able to do finite element analysis and such. instead of the good old throwing stuff at the wall and see what sticks :lol:

btw this is also my 1st "serious" welding project so i do have the feeling that i'm biting off more than i could chew

 

[The Stig]

Hi Overclocker,

I just wanted to confirm: which website did you buy the BHT motor from?

 

[Overclocker]

Hi Overclocker,

I just wanted to confirm: which website did you buy the BHT motor from?

https://www.e-bike-diffusion.com

but i'm not sure if it's still available

 

[madin88]

The Lightningrods "big block" motor, Denzel D4500 or the motor LMX have should have identical performance. Check them out.
From what i know the LMX motor is the most powerful one because it has a 60mm long stator :wink:

 

[The Stig]

Great! thanks all. I was actually trying to confirm y'all are buying from https://www.e-bike-diffusion.com/ since i want to want to buy something from there but couldnt find any reviews about buying from that website.

 

[Overclocker]

flux core is such a dirty process

 

[Overclocker]

[youtube]k5xjtlWbFoo[/youtube]

 

[skeetab5780]

Looks and sounds great! now onto the rest of the bike?? Nice swing design

 

[Overclocker]

thanks. gotta get to work on the rest of the frame. this seems useful

http://cq.cx/tubejoin.pl

 

[madin88]

Swingarm looking strong and solid. I also like the design.

How is the drag (or cogging) of the drive compared to a hubmotor?
Do you plan to use regen?

 

[Overclocker]

Swingarm looking strong and solid. I also like the design.

How is the drag (or cogging) of the drive compared to a hubmotor?
Do you plan to use regen?

tbh i haven't even ridden a hub motor :lol: so i have no idea

yes i'm planning to get something w/ regen even just to save the brake pads. that's another reason why i wanted a drivetrain w/ no chain slack i.e. to prevent any chain issues when using regen.

ideally something w/ variable regen controlled by a hall-type throttle. any recommendations? although i probably won't be able to use very strong regen as my cells (samsung 26f) have low charge rate capability...

 

[trazor]

This build is looking really good!

I would like to try a motorcycle rear hub for my OpenEmoto project. ( https://endless-sphere.com/forums/viewtopic.php?f=28&t=92563&hilit=openemoto ). Yours look very lightweight but strong. Do you know where to get it online? Or a model number? Or which motorcycles it is designed for?

Also, what do you think is the minimal distance between dropouts to fit that hub?

Subscribed, please keep posting.

 

[Overclocker]

This build is looking really good!

I would like to try a motorcycle rear hub for my OpenEmoto project. ( https://endless-sphere.com/forums/viewtopic.php?f=28&t=92563&hilit=openemoto ). Yours look very lightweight but strong. Do you know where to get it online? Or a model number? Or which motorcycles it is designed for?

Also, what do you think is the minimal distance between dropouts to fit that hub?

Subscribed, please keep posting.

you have a very nice build! and our builds have lots of similarities too :lol:

here in southeast asia the 110 to 150cc motorcycles are all over the place. what i'm using is an aftermarket hub for a Suzuki Raider 150cc. but i had it lathed in some places to save some weight.

spacing between "dropouts" is exactly 160mm

 

[Overclocker]

finalizing the geometry...

machined the head tube...

 

[skeetab5780]

Nice i have almost that exact same piece of tubing, its the first step to the thought of building my own frame. You started on a swing first which is a pretty good idea. I would likely get the front done then the back wouldn't adapt

nice progress! watching closely

 

[Overclocker]

Nice i have almost that exact same piece of tubing, its the first step to the thought of building my own frame. You started on a swing first which is a pretty good idea. I would likely get the front done then the back wouldn't adapt

nice progress! watching closely

it's a piece of water pipe which is almost the exact size needed to fit the cups. the machinist only had to remove a small amount. it has a seam i hope it doesn't split :lol:

just for fun i traced it against the sur-ron

 

[SlowCo]

it's a piece of water pipe which is almost the exact size needed to fit the cups. the machinist only had to remove a small amount. it has a seam i hope it doesn't split :lol:

Make sure the seam is facing to the rear so it will be closed in by the frame tubes that will be welded to it. And join those tubes left and right together with small plates.
Great build. Keep going and updating this thread 8)

 

[Overclocker]

Make sure the seam is facing to the rear so it will be closed in by the frame tubes that will be welded to it. And join those tubes left and right together with small plates.
Great build. Keep going and updating this thread 8)

yes that was the plan. we don't want it to split in front and lose the fork :lol:

just got proper front tires. specialized butcher DH, 2ply downhill casing. mounted on super-wide jetset downz (40mm outer width). now building a really ghetto frame jig...

 

[Overclocker]

http://cq.cx/tubejoin.pl

finally the holidays, i think i'll have some time to work on this

 

[Overclocker]