Offbeat
Engineering
Case Study: Swede Harvester
Problem Definition
Early in 1996 we were asked by Scottish Borders swede producer Ian
Campbell of Campbell Produce to look at the feasibility of designing and
building a swede harvester. Ian had previously commissioned a root crop
machinery manufacturer to build a harvester to fulfill his rather exacting
requirements but alas their product failed dismally. Perhaps they were not
offbeat enough in their thinking, who knows! Having studied their design
carefully it was decided there was nothing we could do to salvage it.

Ian had been experimenting with some good alternative ideas of his own
and was keen to incorporate them in to any new design. We agreed to do the
job. Here are some of the design/performance requirements set by Ian



•        Harvest 4 rows in one pass.
•        Capable of discharging from either side into a trailer or box.
•        Fully mounted and therefore maneuverable.
•        Able to work in all but the most extreme terrain and ground conditions.
•        Be fast, versatile, reliable and easily maintained.
Design Considerations – Fundamental Principals
We included several of Ian’s ideas and enhanced or added to them with many of
our own. The machine would have the following configuration:

•        Digging/lifting to be done by 2 contra-rotating tined discs as used on the
Thyregod design. The digging depth and rake angle of which would be controlled
by the 3 point linkage and a land wheel mechanism respectively giving on the
move adjust ability. Drive would be mechanical through an overload protection
clutch and bevel gearbox out to individual tine shaft gearboxes.
•        Crop to be guided from the lifting discs onto a reversible cross conveyor
which would feed onto either of 2 folding elevators depending on direction of
discharge. The cross conveyor/elevator would be hydraulically driven and have on
the move fore and aft leveling and speed control for optimal performance.
•        Being fully mounted the machine could be short coupled and therefore very
maneuverable. Other advantages being that digging depth could be controlled by
lower link height and would not be significantly affected by other adjustments to
the machine. Lifting disc rake angle would be varied by the combination of land
wheel height adjustment and floating top link mount.
•        As the machine was expected to operate on some fairly severe gradients the
rake angle of the lifting discs was made adjustable so that the crop flow over the
discs could be controlled giving optimum cleaning without excess backlog or
damage. Again due to severe gradients it was thought necessary to make the
cross conveyor angle adjustable to avoid build up of crop around the entry points
from the lifting discs and to facilitate an even spread of crop across the conveyor.
This raised an added complication in that the land wheels being mounted on the
rear of the cross conveyor would give significant changes in disc rake angle when
the cross conveyor was adjusted. This was overcome by a neat mechanism
which decoupled the cross conveyor adjustment from the disc rake angle. The
video clips best illustrate these principals.  
•        It was clear even at this stage that this machine would be fast and versatile.
Reliability would be down to careful attention to design and workmanship. The
machine would be constructed in a modular fashion, this would facilitate ease of
manufacture and assembly and in the event of a breakdown individual modules
could be removed from the machine and taken for repair without the need for any
special tools or lifting equipment on site.
Design and Fabrication Process – Computer modeling > CAD > Fabrication
Much to the frustration of our client we spent the first few weeks of this project playing around with ideas - producing loads of
sketches, CAD drawings and where necessary computer applications to simulate linkages and check for interference. Only once
we were satisfied with our chosen design did we settle down to produce more detailed drawings and commence the fabrication
process. The time schedule was so tight that
Brian regularly worked to the wee small hours finalizing the design for the next day’
s fabrication. The design/fabrication processes then ran in parallel throughout the project. At this stage our client really began to
appreciate that our approach was radically different to anything he had witnessed previously, and it was totally geared toward
getting it right first time. Such was our confidence in the design that we decided to paint everything without doing a trial build (a
bit risky but time was now of the essence).
Having assembled the machine we then set about plumbing in the hydraulics and making up the electrical controls. We had now
done as much as we could, so after some preliminary tests of all the functions it was now time to test the machine in a real
situation.
Commissioning
By this time (early April) the swede harvesting season was
drawing to a close and the client had literally only a few rows left
on which to test the machine. It worked very well and our decision
to incorporate as many  
on the move adjustments proved well
founded, as the terrain and ground conditions changed so the
machine could be optimized accordingly. The harvester was very
fast and versatile with excellent visibility, and could fill a 1 tonne
box in less than 40 seconds. Being fully mounted turning at the
headlands was easy causing the minimum of ground damage.
For the ultimate test however we would have to wait until the next
season. This gave us the opportunity to properly guard all
potentially dangerous areas of the machine.
The next season came around and gave us the chance to put the
machine through its paces. One thing that became apparent early
on in the process was the need for some kind of rotary
mechanism to guide the crop onto the cross conveyor, hence the
hydraulically driven rubber tired wheels as seen in the later
captions.
Ten years on – Still going strong
Campbell Produce had several relatively trouble free seasons with the harvester before deciding to cease trading due to
supermarkets setting unreasonable demands. The machine now in its tenth season is operated by R & K Drysdale a large
swede producer who uses it to open up fields and harvest crops not accessible to much larger machines. Aside from the slightly
faded paint work the machine looks and performs as well as ever, having only had the expected wearing parts replaced,
significantly it has
never had any remedial welding, a testament to the quality of design and workmanship.
Inspired by this article
Then check out our other case studies, maybe we could help you turn that bright idea into reality. We welcome your feedback
whatever you think.