Verizino

Sorry to resurrect this post but I've got to ask RCmk, what speeds did you achieve with eh 2s 3.5T setup? Using the exact same setup for a 2s speed build so I'm curious to see what other people have been getting...

Thanks GMballistic, seems like I've got some good tips to start with! I've done mostly bashing and recently started geeking out about the setups in competition racing and speedruns so figured it was something I wanted to start pushing. I flew quads for a few years which is probably the closest thing to speedruns i can think of, as even a small movement on the sticks has a big impact. The BRCA stuff I was aware of but thanks for the ROSSA facebook link. I'd kinda assumed that the events weren't going to be running for a little while yet which should give me enough time to build up the car a bit and start testing. I've never run ultra low turn rated motors before and know the amps is what I need to keep an eye on so was planning to start with a spur to pinion ratio of 4 to allow me to get used to the setup, speedruns and also make sure everything is running true. I want to start lowering the gear ratio when I'm happy how the cars running. Based on what I learnt, the key aim is to minimise the load on these setups just to keep the excess amp draw down as much as possible. That's why I was going to use Alex's advice and try to keep the weight down by looking to a lexan body. The tyres are just the ones I got with the car, no details etc and will almost certainly not be used for proper runs, just for alignment setup and maybe some dyno runs. Out of interest why isn't 2S a good starting point? Also, if you have the time please go on! I'm looking for all the tips I can get 😄

Ah yes, I've already had a look through your build, really great looking project. Shame that you didn't go further though. Also a question about your chassis/body design, why did you go with the taper shape? I saw a picture of that JCB diesel thingy so guessing you were just basing it off of that?

Ok so here goes the current progress update on the car. Motor: Hobbywing XeRun V10 3.5T Mod Motor ESC: Hobbywing XeRun 120A SD V2.1 Servo: Looking for ideas. Battery: Testing on Absima 110C 2S 3800mAh Shorty but will need ideas for the actual runs I got the chassis pre-owned so I figured the best thing was a full rebuild for it and to replace all the screws with stainless as a few were rusted from storage. All fresh and new, ordered a few replacement parts and as you can see printed a couple of mock up battery holders and the servo mount. I'm pretty much just waiting on all the electronics now so I can start testing an tuning the basic setup. All of it should be in by the end of January so fingers crossed it all arrives on time. I'm currently working on a pretty crude dyno, just so I can run physical dyno tests while the weather's bad and to see how the dyno speeds compare to my theoretical numbers. As soon as that's complete and running, I should be able to compare how much of a difference things like new bearings, wheels and gearing will affect my top speed and, probably more importantly, temps. Eventually the car will be moved onto a single carbon plate chassis to minimise drag on the bottom and hopefully take advantage (in theory) of low pressure to generate a small amount of downforce from the rake setup. The plan is to design a body and test it using CAE, then 3D printed to produce a mould for a carbon fibre body layup. I studied aerospace with a dissertation on composites so I guess this will be a test of if I actually learnt anything! It's my first time going down the rabbit hole that is RC speedruns so any tips and tricks will be greatly appreciated as well as any advice about pretty much any aspect.

First of all, Hi everyone! I did setup an account earlier today but as my luck would have it I entered the wrong profile name. Anyways... I've got a smallish RC collection consisting of a 1/16 WPL crawler (ironically my newest RC I got during lockdown), a Team Associated B6, a custom scratch built drift car that's progressing nicely and then the Serpent S411 which I'm attempting to turn into a 2S speedrun car. Like everyone who starts a speedrun build I've got my eye on the current WR @ 132.65mph. As the limiting factor for power is the battery in this case, I've got myself a 3.5T Hobbywing XeRun motor (already technically slightly overvolted on 2S). In theory this is good for more than 70K rpm. Anywho, my question was which ESC should I be going with? I've got two contenders that seem to be strong in my personal opinion; the Hobbywing XeRun 120A SD V2.1 and the SkyRC Toro TS120A Pro-Comp. I have seen a few others but they seem to offer no more features than these two, yet cost a fairly significant chunk more. I'm not too worried about carefully working out my gearing as I'm working on a dyno to help with tuning the setup before I actually take the car out. I'm currently leaning slightly towards the HW because I've had a few ESCs from them in the past and never had one fail (even past the advertised limits). I've been using these forums for years to search for answers, but finally got to the stage where I couldn't find a conclusive answer for a question. I'd really appreciate any help or tips with this project.