Electric A/T wagon project -- introduction

[altavista]

Gentlemen,

To introduce ourselves, we are two French guys who have the project to build an electric A/T utility wagon project. Frankly, we are just fed up hauling our gear (surfboards - cooler - music - chairs...etc...) around when we go to the beach and we see all the other folks doing the same. How pathetic is it to try to haul in the sand two beach chairs, an umbrella and a cooler especially when you want to climb that dune to get back to your car or campsite ?

The first guy is called Philippe. He is the engineer on the team. Working on spreadsheets to find the right power/torque/speed in order to get to the best price ratio for the wagon, worrying about weight, autonomy and so forth.... he wants to build the VW beetle of all electric A/T wagons...

The second guy (me) is called Laurent. I am more the concept/design and operations guy. i am more prone to spend money than Philippe because I want this thing to look good, be extremely versatile and of high quality / perceived value. I don't want this thing to stop working due to sand, water or rust after a few weeks just because we wanted to save a few $$... I want to build the Mercedes-Benz of all beach A/T wagons...

In the end, we will probably end somewhere in the middle...

The concept is to have a very versatile utility cart that can hold its own weight (60 kg) and carry about the same in load (60-80kg), climb up steep hills (20%), moves at walking speed, can brake and do emergency stops

* 4 wheels with tyres (either low pressure sand type or All Terrain. Inflatable or )

* an electric transmission/drive unit. This is where we are unsure about the best choice : one or two motors, direct drive with reduction or a set of pinions/chains, rigid transaxle

* a set of batteries. Right now we are on 2x12V car batteries

* a chassis (probably aluminium due to weight constraints) to hold the above

* a rectangular platform (marine plywood or plastic) that can be dismantled from the chassis for easier transport/storage

* Airline-Style L-Track & L-Track Tie Down Rails incorporated to the above platform to fix items to fix items on top or on tis side

* A set of brackets / Boxes / modules fixed to the airline style track with stud fittings

* a directional / drive control system, probably like a tillerhead.

An italian company (Zallys.com) makes electric utility cars and obviously www.electricbeachwagons.com


I am looking at mobility scooters, electric wheelbarrows and the like to get some design inspiration.

I have read on this forum (electric wheelbarrow post) that geared down transaxle unit was the simplest way to go. less fiddling, enclosed unit....

I would welcome any comment / idea on this project.

Greetings from Paris, France.

Altavista

 

[itsid]

hm.. even with a bit of margin..
a small 1kW motor is all you need to haul 200kg up a 20% inclination at 2m/s or less

200 kg * 9.81 m/s² * sin(12°) =~ 408 N ...
408 N * 2m/s = 816 Watts

so motor and controller can be had for relatively cheap
~100€ for the motor.. like this
~ 30€ for the controller.. like this

two more batteries to step up to 48V and you have most of the electronics covered

Saltwater is not fun to deal with.. so marine grade batteries and wiring is a must if you want it to survive for more than one season.
the motor and controller would have to be tucked away..
I think I'd build a box for them to sit in and use a proper shaft seal for the motor although it eats away a few Watts of power.

Whenever I think of hauling surfboards.. I think of a T1 Bulli.. so I guess
the hauler would be vaguely resembling it's design if I had to choose

I might go so far and build it's chassis around two coolers, one serving as locked compartement / motor-/controller enclosure.. the other just being a cooler.

You can look up how to build a vacuform from cheap parts on instructibles.com and see if it makes sense for you to fab design parts from light vacuformed sheet plastics..
a bit of expanding foam carved to shape as a plug is almost all you need to make them.
(essentially how RC-Car lexan bodies are made thy just use steel plugs)

Keep in mind that no matter WAHT type of transmission you use,
you will pay for it either with money or maintenance effort!
a sprocket and chain transmission is cheap and ges dirty fast (but is easy to clean and maintain)
a transaxle is more expensive and the sand has a hard time to crack it's seals to hurt the gears,
however the aluminium case is affected by saltwater and maintenance will take much longer
than for simple chain drives.

For slow speeds a worm gear might work especially with adding the benefit of a "sudden stop",
since worm gears are mostly not "backdriveable"
so the cart will essentially have the parking brake engaged as soon as the motor is not powering the drive.
(reduced partscount, nearly failsafe brake.. anti theft?)
But with the downside of you not being able to roll the cart, not even a few feet, in case the battery died.

'sid