Shortcuts and shortcuts

Ed, Ask yourself what restorers are doing to get over the problem? A typical solution is to hand select from T45. It is possible to find tube that meets the minimum characteristics of T50 by so doing.
Bruce

Bruce,
Thank you for challenging the logic, I welcome it, as it really forces me to get my head into arcane data to defend the logic, and if it actually develops into a simple, different answer, then that is good. For the record I am not a metallurgist nor an engineer, so nobody should be intimidated into challenging anything I say or propose. Sometimes the most simple observations can cut through.

In simple terms, I understand T45/4130 is provided today in tube wall thickness greater than T50. This is because T45/4130 is designed for welding. Therefore in selecting a 1″ OD T45/4130 tube to replace an original T50 tube, the replacement tube will be heavier. This might be OK if you are patching a few tube members, but will have a more profound effect if you are looking at a total fuselage. Given an aircraft will not carry guns or munitions, these weight and balance affects may be factored into a new engineering analysis, but this is not a simple or cheap exercise. Simply, in the absence of T50 supply, restorers must follow this path.

Creating a T50 supply may provide a more simple restoration path. It then devolves to what is cheaper. Re-engineering an aircraft design or providing a T50 supply.

Acting as an individual, re-engineering is cheaper. Acting in a spirit of mutuality, through short, clearly defined acts of co-operation such as the T50 & T2 Association, may demonstrate that T50 supply is cheaper. Additionally, it will assist many projects. Additionally, it may create fruitful relationships that will increasingly depend on co-operation to sustain the historical aircraft movement. There is very little safe war, or prewar, surplus left and restoration projects are increasingly based on more marginal remains.

I am interested in Hawker Australian Demon. Many of these ended up on Bombing and Gunnery Ranges in WW2, so intact remains are difficult to find. Further, remains left in the bush have been subject to bushfires, not the least associated with munitions on gunnery ranges. The consequent ‘heat treatment’ affects on original material renders it unpredictable. In practical terms 80 year old corrodible remains cannot be relied upon to form a safe structure and I must look at new T50 or some new alternative. A Hurricane pulled from a Russian swamp or Typhoon remains from a crash wreck are equally challenging, compared to more intact remains that may have been secured in the 1970’s.

So I can start with T45/4130, but I must :

1. Buy T45, which is not cheap, and subject it to proof loading, through an independent testing facility at cost, where if it meets T50 spec it will not fail, but where it does not meet T50 spec it will deform or fail. I will try and work closely with the mill to lessen my chances of failure, because I understand that there can be great variability in the same material, and a good mill manager will be able to direct me to promising stock. But I must be prepared for, say, a 50% failure rate in proof loading, so for every lb of accept I must purchase 2lbs of stock, doubling my material costs. Unfortunately the last cold drawing tube mill has closed in Australia, so I must travel overseas or pay for a skilled agent to go through this exercise for me, increasing my costs.

2. Chose at the outset to go for maintaining the same tube weight, by going for a smaller diameter, thick walled tube, subject to heat and mechanical treatments to give me equal performance values to the original T50 or

3. Chose at the outset to go for maintaining the same tube OD, subject to heat and mechanical treatment to give me equal performance values to the original T50, but of greater weight, because T45/4130 has greater wall thickness. In either of these two choices I must substantially re-engineer the entire aeroplane structure. If I amortize this re-engineering cost across my tube stock, I may increase its cost by a factor of 4. In simple terms I must pay for the cost of 4lbs of T45/4130 for 1lb of accept. Depending on how rigorous the re-engineering, it may be 10 lbs for 1lb of accept. How deep do you go ?

4. In re-engineering the entire structure, the practical compromise between financial cost borne by me and the conservatism of the certifying engineer grappling with liability and attempting the task that was originally performed by a room full of stress calculators, mathematicians, metallurgists and engineers is to limit performance factors. So I must pay a lot of money to get a result out of new metal that may only operate at 50% of its potential.

I perceive the value in a remnant airframe to be really its ‘invisible’ sunk cost of engineering, that in the case of an Australian Demon, incorporates a body of work that carries through from Sopwith (Demon aileron hinges are Sopwith Pup hinges!) through the Hart family and would fill a house with reams of maths work costing millions to replicate today. The simple, cheaper alternative is to copy what they resolved so expensively all those decades ago. The deeper I immerse myself in the design, the more I appreciate that every nut and bolt choice was thought through.

The deeper I think about this the deeper the sense of using T50 impresses itself upon me. The upfront cost will be more expensive but the trailing costs of going down the T45/4130 path can, in the passage of time, seem like a harder path to follow. I hope that some of this will make sense to others in a similar position and that by acting for a short while like a farmer’s co-operative, T50 becomes viable for more folk than just me.

Korrect details

Seriously, if you have those hubs lots of people would be eternally grateful – many, many beers in it.

We want USA made 23D40 or 33D50, yes?