For those of you who may have suspected that nothing was happening over the last two weeks think again 🙂
We have been hard at work on doing the distribution drawings for the Presentation Throttle Quadrant, ordering materials, placing orders for waterjet cutting and the 3D printing of the handles etc.
The latter was ordered from Shapeways in the USA and arrived here in South Africa a week later. We were very impressed with:
the amount of information available on each component throughout the manufacturing process and
The great quality of the prints
The components were all printed in “Black, Strong and Flexible” Nylon through the SLS process.
We were very pleased with the way the coarse threads on the throttle handle had come out, and it provides a very strong neat connection while giving easy access to the bomb release button installation.
Throttle Handle assembled
Throttle Handle threads
We had the airscrew handle printed in Premium finish. This entails polishing of the part to reduce the graininess normally associated with SLS. The results, which admittedly are nice, however do not justify the significant extra cost in our minds.
There are many mysteries in aircraft building, secrets that have gotten lost in the mists of time. One of these must surely be the Dunlop Crackle….
Dunlop manufactured many of the RAF spade grips, including those of the Spitfire and the Hurricane. The grips had a non-slip covering with a very particular pattern applied and was known as the Dunlop Crackle finish.
The knowledge on how this was made or applied has now seemingly been lost. As a result, many replicas and restored originals now carry a variety of coverings, including tape, string, leather and numerous others. None of these solutions regrettably reflect the look of the original Dunlop Crackle.
Many hours of texturing on the Heritage Flight Simulation Spitfire Spade Grip have now rendered a satisfactory finish which closely resembles that of the original. We like it, we hope you do too 🙂
The Spitfire Mk.IX Engine Hand Control has turned out to be such a thing of beauty that we have decided to release it as a Desktop Display Model.
This will have many advantages.
It provides the hobbyist with a fantastic working desktop display model.
It provides a glimpse of what is to come for prospective Spitfire Simulator builders.
To aircraft home builders, it provides a full scale working throttle quadrant that can be adapted to their own requirements. (A modification to the Mixture Control will be made for this, currently it works through the triggering of 2 microswitches at the travel extremes. An extension to the lever will provide for an additional control rod)
Those who are contemplating the purchase of the full set of drawings, cutting patterns and 3D components when they become available (target end of 2018), will get the opportunity to assess the quality of the information provided and of the 3D printed components.
The display model will cover the full ambit of information to be provided for the complete build, amongst others:
Waterjet cutting patterns for plywood, aluminium and steel plate
We aim to release the plans for the desktop display and have the components ready for purchase from our Shapeways shop by the end of April.
I am very pleased to say that the throttle quadrant is nearing completion. In the process much has been learnt about the operation of the unit.
For the Rotol (Airscrew Control/Prop Speed) control box we had to deviate from the original, taking the approach instead followed by DCS World. As far as I could discern, the original mechanism operated a vernier cable which was wrapped internally in the box. Operation of the lever in our case will move a control rod, similar in operation to the throttle lever.
The throttle incorporates a gate in the form of a plate which stops forward movement of the lever. Full power at this point is delivered for take-off and climb. By moving the lever to the left then forward the plate is bypassed and the power set in combat mode, which was available for a limited period (5 minutes?) before the engine would call it a day.
The throttle lever when pushed forward activates a toggle switch which powers the circuit to the gear position indicator light. Operators need to remember to switch this off again when shutting down.
Replicating the design of an historical aircraft is a little like playing detective. It requires many painstaking hours of pouring over drawings and doing comparisons with photos of the particular series and model. Nowhere is this more the case than with the Spitfire. While we have some 3400 drawings at our disposal, representing everything that is publicly available, there are many more drawings which may now have been destroyed or are laying in some forgotten filing cabinet.
During the war much of the Spitfire’s production was decentralised, hived off to different smaller fabrication and manufacturing facilities.
These facilities would have been heavily affected by the bombings; even if not destroyed there were power, water and other service disruptions. It’s a wonder that people were able to produce any aircraft at all during this chaos. It speaks volumes to the courage and determination that went into making this great aircraft.
There were also components supplied on a turnkey basis, like the Dunlop Spade Grip, for which there are no formal drawings to be found. In those cases we have to rely on actual measurements taken from surviving equipment.
The basic series of drawings starts with the Mk.I and then variations to these designs were added. There are 38 different prefix codes listed below, signifying some of this variety:
All of this adds immense complexity to the task of recreating the designs. This week we were reminded of this while working on the throttle quadrant.
In keeping with our design philosophy, we are recreating the original Mk.IX quadrant before redesigning to accommodate rapid fabrication, reduced cost and simulator functionality. It’s been hard work but great fun, giving one a sense of what it must have been like in those anxious pre-war years slaving away at a drawing board, trying to get out a design as rapidly and effectively as possible while the spectre of the coming war loomed large.