In consequence of all sorts of criticism on the APPELSPADE a number of tests have been performed to refute that criticism. The critics are by the way almost exclusively people who have not really been working with the APPELSPADE. The tests have produced some surprising results :
The tests have been performed with :
During the tests an iron 5 kg-weight was strapped onto the centre of the blade to simulate an amount of soil to be brought up by the spade. The weight of such an amount varies in practice considerably, depending on the type of soil, the humidity of the soil, and also on the way the soil breaks. Several weighings with sandy clay vary from 4.6 kg to 5.8 kg, so 5 kg represents a good average.
Digging in somewhat heavier soil consists of the following actions :
During elevating the loosened soil, one hand pushes down the upper handle, while the other hand pulls up the spade at a lower point, from now on called point of grip. That point of grip at the APPELSPADE is fixed by creating the halfcircular lower handle, and varies at the common spade. The force of both hands is required to give the spade such a position that the loosened soil remains on the blade, before tipping it. For this the spade has to make an angle with the ground not bigger than 30°.
To determine how big the pressure on the upper handle has to be to keep the loaded spade in the required position, both spades have been suspended at the point of grip. The APPELSPADE has just one fixed point of grip, namely the halfcircular lower handle, at 47 cm from below. The common spade has been tested while suspended at 47 cm from below, and also at 55, 63, 71 and 79 cm from below. To suspend the common spade, a clamp is needed for stability. On the upper handle the pan of a balance was suspended on which then weights were placed, till the spade made an angle of 30° with the ground. Thus was determined what mass (or what pressure) is required in total (weights + pan + chains) to get that position of the spade. The results of these tests are :
Type of spade................ Point of grip...................... Force on the upper handle... APPELSPADE 47 cm high 1.75 kg common spade 47 cm high 2.87 kg common spade 55 cm high 4.30 kg common spade 63 cm high 6.01 kg common spade 71 cm high 8.75 kg common spade 79 cm high 12.75 kg
The APPELSPADE and the common spade both suspended at point of grip at 47 cm high.
From this two things appear clearly :
This is what the lower hand ultimately has to lift :
|
APPELSPADE.................. |
common spade........... |
|
|
weight of the spade |
3.62 kg |
1.99 kg |
|
weight of an amount of soil |
5.00 kg |
5.00 kg |
|
pressure on upper handle |
1.75 kg |
2.87 kg |
|
total |
10.37 kg |
9.86 kg |
With the APPELSPADE the lower hand ultimately has to lift 0.5 kg more (or 5% of the total mass), while the upper hand has to push 1.12 kg less. Lifting 10.37 kg with a straight wrist however is considerably less straining than lifting 9.86 kg with a crooked and twisted wrist ! A simple test : lift a 10 kg-weight (with handle) with a straight wrist. This can be kept up for ten minutes or more without any problem (ask any weight-collector, like me for instance).Then (after a break to rest the muscles) lift a 5 kg-weight (with handle) with a crooked and twisted wrist. After one minute already that's no longer pleasant, and after two minutes it is downright painful. This explains the painful wrist after only a short time digging with a common spade.
On the drawings below is shown where the point of gravity lies in the APPELSPADE (on top) and the common spade, both loaded with 5 kg. The spades balance on a triangular piece of wood (the black triangle).
