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Signing UpStep 1: The Chassis
The chassis was a simple "Ladder" design made from 19mm aluminium square section tubing. This is easy to work and light as well as moderately low cost.
The various sections were joined with aluminium plates and pop rivets. We followed a Greenpower design as the basis for our car but made numerous changes along the way.











































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You can get DC motors second hand but they are surprisingly rare these days. About the best source is Ebay and ex golf cart motors or up to 300 watts (claimed) electric scooters.
2.5 hp at 130 VDC
17.2 AMPS
7090 RPM
25C
Class B
Thermal switch: 120 VAC MAX. 1800 VA MAX
Im kind of unsure as to what most of these mean lol and would it be a good candidate for a small go kart like yours?
2. Other than that it looks very useful.
Power is a function of Voltage and current so As you increase the voltage you can reduce the required current for a given power. This is why the F1 KERS systems use 300 volts + to power their system.
thanks for the comment.
In actual fact it will fall somewhat short of this if you expect it to recharge and have much of a life.
Assuming the motor is 24 volt you may get 3/4 to 1 hour real running out of it. In principle the 100 watt motor will draw 4.amps to produce 100 watts at 24 volts.
100 watts is a little small for powering much other than a very light weight scooter. 200 - 250 would be better and not a lot more expensive.
in this car a 70 Ahr battery gave us about 2 hours running flat out - 30 Mph.
You have to understand the rules. The drive must be able to exit the car in under 6 seconds - a wheel gets in the way and to make it removable as in F1 is just too complicated. This isn't intended to be a raod car but has been built for a precise purpose.
As to having poor drivers in the UK I see in the current Formula 1 line up drivers from the UK - Australia, Germany Scandinavia in fact all over Europe and south America but No North American drivers have driven since 1993 and ever won the drivers championship.
Perhaps your driving experience is more suited for driving round simple oval circuits?
it's easy to be critical when you don't have the full picture!
A easy way to make a quick disconnect steering wheel is to use a socket wrench extension and a socket with a nut welded into it that is bolted to a steering wheel.
Use air socket wrench parts as they are better built for this purpose.
You can also use impact wrench extensions and the universal joints on them with small gas and electric motors if you have to mount a motor offset.
Ensure you FULLY understand and comply with the rules.
Brakes are a BIG failure point - make sure the exceed the minimum demand.
When you race take spare tires and inner tube (You will get punctures)
Make a tool/parts list make sure you take them all.
Get to the race early so you can unpack, set up and get scrutinised.
Make sure every member of the team has a job to do and does it -
Practice packing and unpacking, changing batteries and drivers a LOT.Try to have more team members than the minimum or you will find some days not everyone turns up.
try to involve parents.
Our down fall was that it took so long to change the tire that put us out of the running.
Build simple and reliable, you will outlast may of the fancy, even corporate entries who have spent BIG money on their vehicle.
Find somewhere to let your drivers practice driving. This can be really difficult as wide open spaced are few and far between.
Remember every year you need to bring in new members. We used to keep the car in the school foyer as an advert - It not only impressed pupils but Ofsted as well.
try hard to get a range of staff interested so your not short of adults when you need to race. i was lucky that out groundsman was interested and almost always available.
I have decided to split the current through 2 relays as I couldnt find any 40A relays. I am using 2, 350w 24v 19A 2550rpm motors geared down so they have suffient torque.
I am using light wieght alluminuim for the frame
Thanks
Oscar
How about brakes? Stopping is more important than going!!!
Have you modified an existing kart or built from scratch. Getting steering right is very tricky.
The steering is still needing to be perfected.. The spindles and the steering column work fine its just i need to find sutiable push rods and joiners. I used m6 bolts (the long ones you can cut to size) but it keeped locking up.
Thanks
Oscar
Well There are some serious issues here.
Please people who are interested read the whole instructable AND follow the links for further information/
Please research what others are doing. IF we could get 100 MPH from 2 car batteries and go 500 miles then Ford etc would be already doing that!
Lastly please attend to the points below.
1. This is a BIG task - I also made an electric car fro my collage degree and it took me almost a year of very long hours and hard work to do - make sure you can finish the task.
2. You will not get 50 - 60 MPH and a reasonable distance on a couple of car batteries. THINK - if this were possible then commercial manufacturers would be doing it.
3. You must do some in depth research there is a LOT of information on the web, this is only a starting place. You must look to see what others have done and how they did it or you are bound to fail. As a teacher of design I am worried that you don't have enough grasp of the essential issues to complete the task.
4. At best you will probably get about 30 or 40 MPH on the flat for about 2 hours from 2 car batteries - so a range of about 60 miles.
5. The most energy dense electrical power supply at present that is easily available is Lithium ion batteries like in mobile phones BUT these are going to cost you a LOT. commercial cars combine a HUGE power pack with a higher voltage motor to get a better power to current rate.
6. Our motor was 250 watts and if you rad all of the instructable and follow the links you will see runs at about 2000 RPM and was geared to give 35 MPH at the wheels - I leave it to you to work out what the gearing has to be as it depends on the wheels you use.
7. Our car cost us about £1500 to build say $3000 so it isn't a cheap project to do well.
8. Your better bet would be to develop a part of such a system and show how it is integrate into the whole vehicle.
9. For a commercial day to day car you will need to look at Pulse width modulation speed control. This will give good control without wasting energy, Energy recovery on braking (KERS system). A suitable material and construction for a VERY light weight body/chassis. A suitable source of mechanical running gear. Some way to steer and some way to stop the vehicle.
10. As I said at the start It is a long and complex engineering problem, it can be done - we did it, but you MUST ensure you have the time and skills to complete the task.
Good luck
I would like to know what gear ratio you are using? And does gearing the motor down increase the torque. eg. a 300w motor geared down so 1 revalution of the wheel is 5 revalutions of the motor, would mean the torque is equivelant to 1.5kw motor?
thanks
oscar
Thanks
The breaker protects against excess current - initially we set it to 75 amps but later changed it for a 100 amp breaker - That is a LOT of amps. -
The motor is controlled by a simple on off push button - this quite enough for the type of racing was were doing anything more complicated adds weight and gives a higher failure chance.
It is IMPORTANT you use correctly rated automotive wire for this as the motor can and does draw around 75 to 90 amps on occasion. A car battery is quite capable of melting insulation and wire and starting a fire so safety MUST be a first concern.
I have two motors and each one draws about 19amps. I am also using a automotive relay to switch the power on and off. I know the the gauge of wire for the motor connections have to be thick but for switching it on, does it have to be thick?
My gauge of wire is that type out UK (united kingdom) extension leads, I dont know how to measure it ?
Oscar
Are they driving the same wheel? if not will they run at the same speed?