Did some research on tire pressure monitoring and looks like there just isn’t an accurate and cheap solution that isn’t fully DIY. I set about 150$ as the max budget I’m willing to pay (I feel like that’s already a lot for this for an esk8…) and it’s barely a small fraction of any motorsport grade COTS solution.
Automotive grade TPMS sensors on the other hand don’t have sub psi precision, so would be kind of useless in kart wheels where my operating pressures range from 6-15 psi depending on the tire. Not to mention the up to 90 second period time between sent out signals.
I’m kinda considering building a small PCB with some BLE or RF capable low power consumption microcontroller and this honeywell pressure sensor. This should have roughly 0.005 bar / 0.075 psi precision which is plenty good for me. But not 100% sure if it survives the bead popping pressures… MPRLS0030PG0000SA
It’s quite a bit of work so this will be a pretty low priority sideproject.
Designed the double stage around the SSS56154 motors… It looks absolutely crazy on the back of the board.
It’s pretty bulky (and heavy due to the size) but as long as I want to stay on mod2 (which I want to) then I’ll have to live with that. I’ll also probably scratch my head a bit when setting it up in the CNC, but I love the completely insane look.
That said I might make a mod1.5 version as well later down the line if this turns out too heavy once I actually have it built.
Yes! There’s a couple holes to choose from which is copied from my current raceboards binding mounting holes. I have the front foot’s and the rear foot’s holes on both footpads and they are also mirrored for goofy, hopefully that gives enough options to be comfortable for everyone. They work by taking the footpad off and inserting M6 countersunk screws to the bottom of the footpad, then the binding posts and nuts on top.
My plan is to continue running the F5 bindings and heelstraps, but I didn’t want to waste time modelling them. I do have a rear footstop modelled also for those that only want to run a front binding.
Regarding the footpads, the plan is running studs instead of griptape like on an EUC pedal. It grips better and the adhesive of griptape won’t be causing problems either. It also allows to cut down the weight of the footpads.
That’s a swingarm style suspension inspired by Radium’s solution, though I have different geometry and goals. I’m not using it for suspension purposes, the kart wheels are already great at eating up bumps. I have it to emulate a mountainboard style deck’s tip angle flex, while being able to use a very rigid chassis to eliminate all torsional flex that flexy decks tend to have. The main effect I’m looking for is increased truck angle in high G turns, as this allows running a very stable setup with low angles without sacrificing any turning.
Furthermore this also allows some fine tuning of your line in the corners, the more weight you throw into a corner the more turning you have, and you can also play with compression and decompression going into / coming out of corners to have this same fine adjustment. This essentially does the exact opposite effect as slip angle would do in a corner with tires like BRPs, and I find it really benefits precision and control of very low slip angle tires like the karting tires.
Designing around skate bushings for this suspension part is the “easy option” to adjust this deck flex effect. I was considering making a more complex suspension but it’s hard to argue with the simplicity of this design, not to mention the small space requirement. If this simple solution can achieve the results I’m looking for, then probably no need to overcomplicate.
Spent a bit of time polishing the swingarm design and made this quick animation
For 5mm bushing squish height wise (I have a feeling this will be roughly the max range) I gain 7.5 degree truck angle and a reduced wheelbase by 15mm per truck which is a nice side effect. Plus there’s a downward travel of 15mm, which I think is small enough such that the leverage doesn’t get messed up too much, especially since the standing platform is a few mm over the axle as a starting point. And it’s definitely good enough to eat up some bumps also.
This would net a max turning increase of about 30%, and if it’s too much, it can be reduced with harder and higher rebound bushings, or even by using a shorter bushing on the top.
Not sure how much of this effect I actually have on the current board in a quantifiable manner. I need to mill things out and test ride. Aiming for mid February to have everything milled out for the chassis.
On another note, I’m considering making and testing an 8M belt kit for reachers to hopefully offer a reliable but quiet drivetrain option.
That would be awesome, thank you! I’ll send you a message to discuss some details later.
I’ll see if I can estabilish a baseline to have a rough idea what makes most sense to test. I really want to knock out a functional prototype that I can race on and showcase at esk8con.
I’m pretty sure I have access to a hydraulic press based material tester at university that should be able to apply the same load that the suspension will, though I haven’t used it yet. Need to ask the prof responsible for it but if it works out… I’m pretty sure it can create some stress vs strain curves for some bushings I already have to aid rebound, formula, and shape selection, would be some very interesting data. Maybe it could even give a rough idea on duro selection, as the math to estimate the force supported by the bushing should be possible to calculate. If I can narrow it down somewhat that would be great.
I’ll actually need to modify the bushings for 12mm inner diameter, as I have limited trust in a 3/8” hardware here, and I really want to avoid broken kingpins, so I was planning to go with a 12.9 grade M12 kingpin
Made a couple refinements and added some extra adjustability in the design. It’s possible to run 30 or 35 degree ends now, and the bushing mates an aluminium-bronze alloy insert, which has excellent wear resistance and looks really cool. Is it overkill? Probably. But I do have some minor wear in some of my bushing seats, so maybe it could be worth it long term.
Also there’s one ride height option added into the swingarm itself, there’s a 12mm riser which can be either above or below the swingarm, changing height. The picture shows both positions filled but only one of them will be filled at a time. It still allows the swingarm base to be clamped from both the top by the chassis and the bottom by the bellypan, this way the bellypan adds significant torsional rigidity to the system, since it’s also bolted to the chassis.
The plan so far was 28x12x12 3001 double row angular contact bearings, at a slight preload. I wonder how pivot tubes could work, it’s definitely an option, but I wonder what gives more precision. There’s a pretty big lever arm from the axle to the pivot.
If I were to use pivot tubes I can only really see that done with bolt on pivot arms, and that definitely adds a bit of complexity.
