I stumbled upon vex robotics website over the winter, probably following some rabbit hole that started somewhere here on the sphere- can't remember now. Anyway, check out the Vex Pro portion of their website: http://www.vexrobotics.com/vexpro/?ref=logo. They've got tons of cool goodies for us DIY reduction types: customizable and user serviceable planetary gear boxes, dog shifter mechs, ball-lock shifter mechs and all sorts of gear, sprocket and HTD5M belt stuff . This thread will cover my foray into using their ball-lock shifter mechanism in a left side drive (LSD from here on out) 2 speed reduction box.
I picked up this unit http://www.vexrobotics.com/217-3290.html from their site and some assorted gears, bearings and shaft. The unit I think I'll actually use for this first attempt is going to be the 60/44t model, located here http://www.vexrobotics.com/vexpro/motion/gearboxes/ball-shifter/217-2792.html, but some of the mating gears (24t with 1/2 hex bore) are sold out on the website until May 1st. The 60/44 shifter mech will allow a reduction of 2.5:1 (60t to 24t), where the 50/34 model I've got on hand will only do 1.47:1 (50t to 34t). The extra bit of redux from the larger diameter 60/44 mechanism will allow a simple, smaller 1st stage belt reduction and the final reduction will happen at the rear wheel via #35 plate sprocket bolted to disc brake mounts.
At this stage, I will be using a Tacon Bigfoot 160 motor (6364 size, 245Kv) powered via VESC (if you don't know about the VESC, check out vedder's web site and forums: http://vedder.se) @ 10s Lipo. I will probably make this a dual motor set-up, but I want to see if it will run on just one of these little guys first. Optimum set-up for the VESC would be to run a 190Kv motor at 12s (pretty much the established voltage/Kv limits), but I've got a tacon on hand so that is where I will start 8)
Here's what I've got on hand:
View attachment 3
A screen grab of some of the component's in my sketchup play pen:
And a closer look at the current proposed assembly:
The plan is to mount the unit from the bottom bracket a la GNG/cycle/etc and have the gearbox output shaft just in front of the BB on the left (crossbreak-style). At this point the primary reduction will be via HTD5M belt, 15t driver/42t driven for 2.8:1. Ball-shifter mechanism reduction is 60/24 or 2.5:1 in low and 44/40 or 1.1:1 in high for a spread of 2.27x. Final drive will be via #35 chain with a 12t driver and 60t driven on the rear wheel for a final redux of 5:1. Total system reduction in low gear will be 35:1 and 15.4:1 in high. Aiming for around 20mph in low and low 40's in high (probably need dual motors for that speed, reliably).
Pros
-compact: should be able to get the housing height under 4" and total length under 9" for a single motor and 12"ish for a dual motor set-up
-relatively cheap
-very customizable/tunable
-Should be able to shift easily, even under load>> according to my internet sleuthing
Cons
-durability/torque handing is a complete unknown: can't find specs on their site, best I've got is the 1/2" hex output shaft is rated up to 116 ft-lbs (which means my motors should not exceed 16.6 ft-lbs>> I wish
). I've found nothing relating to the aluminum gears, only negative reviews I've seen related to the earlier version plunger not being up to task, but this has been remedied by using a chromoly shaft now (hardened? unknown)
-Noisy?- straight cut aluminum gears, can't imagine it will be silent
-everything but the guts will need to be fabricated
I picked up this unit http://www.vexrobotics.com/217-3290.html from their site and some assorted gears, bearings and shaft. The unit I think I'll actually use for this first attempt is going to be the 60/44t model, located here http://www.vexrobotics.com/vexpro/motion/gearboxes/ball-shifter/217-2792.html, but some of the mating gears (24t with 1/2 hex bore) are sold out on the website until May 1st. The 60/44 shifter mech will allow a reduction of 2.5:1 (60t to 24t), where the 50/34 model I've got on hand will only do 1.47:1 (50t to 34t). The extra bit of redux from the larger diameter 60/44 mechanism will allow a simple, smaller 1st stage belt reduction and the final reduction will happen at the rear wheel via #35 plate sprocket bolted to disc brake mounts.
At this stage, I will be using a Tacon Bigfoot 160 motor (6364 size, 245Kv) powered via VESC (if you don't know about the VESC, check out vedder's web site and forums: http://vedder.se) @ 10s Lipo. I will probably make this a dual motor set-up, but I want to see if it will run on just one of these little guys first. Optimum set-up for the VESC would be to run a 190Kv motor at 12s (pretty much the established voltage/Kv limits), but I've got a tacon on hand so that is where I will start 8)
Here's what I've got on hand:
View attachment 3A screen grab of some of the component's in my sketchup play pen:
And a closer look at the current proposed assembly:
The plan is to mount the unit from the bottom bracket a la GNG/cycle/etc and have the gearbox output shaft just in front of the BB on the left (crossbreak-style). At this point the primary reduction will be via HTD5M belt, 15t driver/42t driven for 2.8:1. Ball-shifter mechanism reduction is 60/24 or 2.5:1 in low and 44/40 or 1.1:1 in high for a spread of 2.27x. Final drive will be via #35 chain with a 12t driver and 60t driven on the rear wheel for a final redux of 5:1. Total system reduction in low gear will be 35:1 and 15.4:1 in high. Aiming for around 20mph in low and low 40's in high (probably need dual motors for that speed, reliably).
Pros
-compact: should be able to get the housing height under 4" and total length under 9" for a single motor and 12"ish for a dual motor set-up
-relatively cheap
-very customizable/tunable
-Should be able to shift easily, even under load>> according to my internet sleuthing
Cons
-durability/torque handing is a complete unknown: can't find specs on their site, best I've got is the 1/2" hex output shaft is rated up to 116 ft-lbs (which means my motors should not exceed 16.6 ft-lbs>> I wish
). I've found nothing relating to the aluminum gears, only negative reviews I've seen related to the earlier version plunger not being up to task, but this has been remedied by using a chromoly shaft now (hardened? unknown)-Noisy?- straight cut aluminum gears, can't imagine it will be silent
-everything but the guts will need to be fabricated
