IET Formula 24
It looks like you're new here. If you want to get involved, click one of these buttons!
IET Formula 24
IET Formula 24+
Frequently Asked Questions
IET Formula Goblin
Parts for Sale
The Corporate Challenge
Did I hear right? No push starts in F24 in 2018.
IET Formula 24
I'm sure the commentator mentioned this at the finals yesterday. Did it happen or did I imagine it?
Yep, the start of races will be unassisted like in F24+, see S4.4 in the 2018 regulations:
http://www.greenpower.co.uk/sites/default/files/Technical and Sporting Regulations 2018 V1.pdf
So just wondering how teams are dealing with this? We've got a single speed car and we can gear it down to reduce the load at start up, but any other, relatively simple solutions? Built a car a few years ago with a gear hub but the drivers found it very hard to select the right gear. Would prefer to keep our car single speed. TIA. Alex
Some F24+ teams (who've had to start unassisted for years), most notably Jet, used a simple system of two relays whereby one relay pulled from one of the batteries and the second relay then ran a 24V circuit.
Other systems work just as well if not better. Some cars run a simple 'Soft Start' system which is basically a variable limiter which governs power output on a gentle slope during startup, and after a short while simply allows current to be drawn by the relay in the same way as it would be if this device was not in place.
The ideal solution is an Electronic Speed Controller, or ESC. These employ a PWM signal from a potentiometer on the throttle or similar to govern the power available to the motor in line with the amount of throttle input the driver gives. Chipping Sodbury offer a 'GpSpeed' motor controller kit at a relatively low cost if it's not something you'd be confident in making but you'd be interested in a system like this.
F24+ team here, I've been running my basic setup of a relay operated by a switch and a singlespeed drivetrain, no fancy PWM or soft start electronics for the last few years, haven't had any issues and I get to shoot off the line compared to others ;). Just make sure that your electronic is rock solid ie reasonably thick guage wiring for the main circuit and decent end connections as the higher current would heat/melt stuff that wouldn't done before due to the substantially higher current (~ 50% higher on startup imo).
Interesting to see that Greenpower hasn't really beefened up the electronics in the regulation for the interest of safety with at least minimum gauge wiring for main circuit, and possibly higher value circuit breaker and isolation switch, after all these are electric cars and can be dangerous if done incorrectly or mistreated.
I don't really run any speed controller or fancy electronics (only got echook nano) because I like to keep my cars simple and bulletproof regardless of weather. But some teams do and use them to good effect if they need to manage their energy usage. The difference in current will vary between fast and slow tracks as gearing will make a difference although I wouldn't adjust it so the start is easier, aim for your race avg speed.
All of the wechook cars were running echook Nanos (or equivalent home brew systems) with PWM motor drivers. I will eventually get around to documenting the design we used that is eChook Nano compatible but the build is fairly involved and requires some decent (powerful) soldering equipment really.
However! We almost always blasted off the line on 100% PWM duty anyway since it was so fun, this is pretty much the same setup as with a relay anyway (as mentioned by Stealth above). We never had an issue even pulling away in our high gears. I imagine the lower gearing used in F24 will be even easier on the current spike at pull away.
Stealth brings up the good point that large diameter wiring is necessary, we use 16mm2. Larger diameters will reduce voltage drop anyway so you'll get that as a free advantage.
We also use one of these:
(cheaper sources may be available online)
We would position this near the drivers foot if possible so that should it 'pop' and cut the cars power we could manually reset it, this was never required but always nice to peace of mind should we try and do a burnout start on a hill...
Powered by Vanilla