Next Moves

It’s been a bit quiet on the velomobile front for a few weeks because I’ve been working out production costs for Atomic Duck M0.1 to produce the prototype and for putting it into batch production.

In short: the current design is too expensive. The lowest price I could produce the M0.1 for sale for is around £1650 (as batches of 10, singly it’s £3600). As this is already above my target price for the final kit, it’s clear that the design is not to yet refined to my manufacturing requirements.

While I could mitigate some of the production cost by going abroad for production or producing larger batches of kits, this would just be papering over the problem with money. If production is dependent on exchange rate or living cost advantages to get kits at the right price, then local production will never be viable — which loses one of the great advantages of open source engineering.

Instead, I’ll be spending time re-engineering the chassis to reduce the cost of production. I’ll be looking particularly at the font axle cross tube (A001_P009_R001) and every folded aluminium piece. The cross tube needs a mandrel bend as parts of it’s manufacture, and each fold in the 3mm aluminium sheet needs an industrial brake press; which, although they are common practice in the metalworking industry, are expensive to use at low volumes because they are manual processes and the equipment required makes them effectively out-of-reach for home production.

But we’re still here, still working on the Atomic Duck. Keep watching as we get closer to production…

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4 Comments

  1. alphydan
    27th July 2011 at 10:02 am

    Hi Patrick,

    Would the use of jigs make it cheaper to self build? I know the first objection would be, but you would only use the jig once!, so it would be too expensive.

    But what about a “shared” jig. The customer buys the plans, sheet metal and bike parts. He also gets a compact jig she/he can easily mount for 2 weeks. Builds the velomobile and sends the jig to the next person.

    Would that work? Sort of a Jig Rental service to spread the cost?

    • Patrick Fenner
      28th July 2011 at 11:58 am

      The extent of jigs for building is having a flat surface to build onto (like a big sheet of MDF levelled on sand), all of the structure is self-jigging, so it positively locates in the correct position and angles. And one of the design requirements was to use standard production techniques that don’t need extra/specialist hardware to make the parts. The additional cost has come about more from the cost of setting up some of the manufacturing processes.

      For example: having the front axle tube bent costs around 6 times the cost of having the same straight tube cut with a laser tube cutter. The additional cost comes about because of the time required to set up the mandrel bending machine to make the bend to the correct angle, compared to the setup time for making cuts on a laser cutter.

      For each set of bends that is made for an aluminium part, the brake press has to be set up for the backstop distance to put the bend at the correct point, and the jaw movement to make the correct angle bent. Each one of these is a setup cost for producing the part, so if you make one hundred parts, that’s one hundredth of the set-up cost per part.

      At batch sizes of one or ten parts, that cost can be quite prohibitive; for some parts I have quotes for, the cost of single part production is 8 times the price per item in a batch of 10!

      • alphydan
        29th July 2011 at 3:14 pm

        So that is precisely the question. Can we not bend that tube ourselves using a jig? Can we not bend the sheets with some form of bench vise and jig rather than a brake press? // this may be absurd … as I have no experience with alu manufacturing … but maybe some lateral thinking could help :)

        I can also ask fabricators here in the isle of wight if you want a different quote.

        • Patrick Fenner
          1st August 2011 at 8:11 pm

          Ah, I see what you mean. Unfortunately, the forces involved in the bending are substantial, and are out of practical reach for hand tools.

          It deserves a longer explanation, and I’ll prepare an article on it, but the short answer is that the bending forces are in the tens of tonnes for 3mm Aluminium sheet, so the machinery it’s self is good and heavy.

          Lateral thinking is good, and I’m always open to ideas.

          I’m working under the current idea that the design just isn’t refined enough yet, the bending thick sheet never seemed ideal, so I’m looking to do things like, omitting bends where I can use cut tube instead, and I’m currently doing some calculations to use a glued wood laminate for the front axle cross tube — self jigging of course. The only part that I’m expecting to remain as bent sheet is the rear hanger, as I don’t have a suitable design concept to replace it.

          If you can find fabricators that will produce the parts singly or in batches of ten, I like to hear about them. As I’ve said before; I’m looking for producers anywhere in the UK, or even abroad.

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