A New Pedal Powered Rotavator

Hello All!

When you prepare a garden bed, do you use a Spades, Shovel and Forks, but find it is a lot of hard work and time? Or do you use a diesel rotavator to get the job done even though its not eco-friendly?

I am a product design student in my final year at Northumbria university and have to undertake a major final year project which finds a problem that a product can solve; I have been in touch with a community that is constantly increasing its ability to be eco-friendly, sustainable and provide for itself from its surroundings; such as, growing their own veg for the community etc. The community have suggested a pedal powered rotavator may be a good idea, because they are spending a lot of time and hard work to prepare the beds just using spades and shovels to tackle 1/4 of an acre at a time yet our legs are much stronger than our arms and may be able to do the job more sufficiently.


So do you think that it is a good idea and there is a need for a product like this? Or would you even want a product like it for your allotment/garden/community yourself? All opinions and thoughts will be greatly welcome!

Suze

 

This must be a joke.

A pedal-powered rotovator?

Have you any idea how much power would need to be generated to turn over a compacted, wet, clay, soil?
As a design student you must be aware of the huge mechanical advantage has an ordinary garden spade and yet the amount of force needed to turn over just a spadeful of heavy soil.

The affect of a small petrol driven rotavator on the environment would be minimal.

 

World class cyclists often put oversized tyres on mountain bikes then deflate them and ride on sand as part of their resistance training. Have you ever tried that?

I'm very fit and strong but my brain hurts thinking about the physical effort a pedal powered rotovator would require.

 

I can see it now, the operator pedalling away like mad on his rotovating machine and the big wide wheels, necessary to support this Rowland Emmett contraption and the driver, compacting the soil previously turned.

 

I think we have to consider power developed by a petrol engined Rotovator. My soil is heavy clay and I have a 4.5hp Rotovator. It struggles with compacted clay so it is necessary to dig compacted areas over first. The power developed by the engine is capable of cultivating heavy clay because of the gearing reducing the revs. and increasing the torque to move the clay. A cyclist would never be able to attain the necessary revs. to supply the power and only develops a fraction of a horse power.

 

There was a telly program where a family of 4 spent the day (or weekend?) in a house powered by electricity from cyclists (in an adjacent warehouse). Perhaps this should be a husband-and-wife machine? or maybe the whole family? ... or the whole neighbourhood? :o

 

Perhaps a pedal powered way would be:-
Cycle frame on a fixed stand, chain drive to a generator (24v), wired to battery set-up.
Use a Mantis or similar Rotavator (240 volt AC) connected through an inverter to the battery set-up for supply.

 

As most others who have replied have suggested - I don't think pedal power is viable.
You just MIGHT get away with a pedal driven system that pulls a plough up the plot via a rope and powered by two or three 'cyclists'. Though to be honest I doubt if this would work as well as a small hand plough pulled by two folk and steered by one.

What the group might like to think about is the green option of using recycled cooking oil to power a normal rotavator.

 

I can't get too excited about using recycled cooking oil as a fuel. A well maintained petrol rotovator is probably less harmful to the environment than a cow.

 

A very ingeniuos suggestion :gnthb:

But I can see some probable difficulties -

1 - The energy required to turn a 24V battery charging generator at the revs required is quite considerable and I'm not sure it would be feasible via pedal power - certain not by a single 'cyclist'.
2- Charging a high capacity 24V battery takes several hours,particularly if the charging current is low as it would be from pedal power.
3 - A very beefy invertor would be required to supply sufficient power to a 250V rotavator.
4 - Invertor and 24V battery would have to be mounted on the rotavator which would significantly increase the energy required to drive it and would also make it more prone to sinking and much harder to handle.
5 - The efficiency of the energy conversion chain will be pretty poor as losses occur at each stage of conversion.

It would certainly be very interesting if someone can be bothered calculating energy input-output for this system. I might be completely off the mark with my assumptions.

 

Dave W, you are quite right, the energy required would be very high to get the Rotavator turning the ground over. It may be more feasible than a pedal powered Rotavator. As a cyclist I know that the only cyclists capable of developing enough power are those in their teens and twenties. Certainly the average gardener would be unable to do so.