Bunt's Concept 400 Series Tire.
The motorcycle tire featured on this page was produced for several reasons. There is a fashion for wide rear tires on custom motorcycles, I like the 'cartoon' aspect of the size, but the main reason was to demonstrate one of the many materials I can use in the course of my work.
In this case it was to produce a realistic concept model that had the appearance and tactile feel of a real tire. Some of the viewers of this page who are capable of this work may wonder why I chose the method of production shown on this page. The answer is simple; because this is a self-promotional item, it had to fit in with my customers work shedule. By splitting the components into smaller sections, I could easily complete a section as and when I had the time. For any customer who required a similar project a more appropriate method of producion would be utilised.
The whole process is featured on this scrolling page. I thought it more convenient than spreading it over seperate pages. Starting with the initial model, the process unfolds to show all the stages involved to arrive at the finished tire. I hope you find this feature of interest. If you have any questions, don't hesitate to contact me.
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Framework
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The framework for a one sixth segment of half the finished tyre was fabricated to act as a support for the styling clay, which will produce the tire surface. The frame incorporates the tire centre point to which the curved board is concentric. The 60 degree end plates have to be totally accurate if the finished mould sections are to fit together correctly. The frame has been infilled with two-pack foam.
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Prior to applying the styling clay, the main surface area receives two coats of shellac to aid adhesion for the clay.
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The framework is now ready to have the styling clay applied.
...........end of Framework
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Additional clay added to build up the form.
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A template is produced to the exact profile required and attached to a holder. The curved base plate can now be seen to act as a guide to define to required form.
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Further clay is added to the low spots.
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More work with the template to acheive a regular surface.
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Now work starts on the sidewall area of the model. A hand held template is used to rough-out the basic profile.
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Filling the low spots and reworking the form.
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Now a profile plate has been clamped in position to act as a guide for the template.
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The form is now complete and is ready for detailing.
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A 'steel' is used to remove the ripples caused by the template.
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More work with the steel refines the surface. The remaining low spots ( showing as the dark areas ) are only microns in depth.
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The finished form polished and ready for the next stage.
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Close-up of the Bunt's logo and tread pattern.
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Here the tread shapes have been completed and the surface is coated with shellac.
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Work starts on producing the tread depth.
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This image shows the logo and tread pattern areas cut and removed.
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Surface is covered with masking tape and the Bunt's logo is positioned. The outline is then marked through to the clay.
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This is the clay model ready for a female mould to be taken from it. Note the building up of a flange area, particulary the top curved section on the highest point of the model. This is to poduce a two-part mould, so that the mould will release from the model, allowing for the undercut produced by the tread pattern.
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The main section of the GRP mould laid up with a strengthening piece bonded in to support the side flanges.
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This view shows the temporary flange piece removed to allow the second section of mould to be laid up.
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Second section of the mould laid up.
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The mould cured, trimmed and the side bolt holes jig-drilled for later use on the final mould sections.
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The mould partially stripped, with the main section left in place so that additional sidewall sections can be laid-up. The sidewall section shown here has a plain surface.
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The clay model is now prepared for the next section which incorporates the sidewall lettering. This raised lettering (2mm) was cut and bonded to the sidewall area. The sidewall plates were replaced and another lay-up carried out.
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After a further moulding was completed with the tire size featured, this was the basic mould from which the final model would be produced.
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It was decided to incorporate some silicon change pieces in the final model so that there would not be any problems with the lettering. This image shows the fixing bolts for the silicon insert jigged into position before the silicon is poured.
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The insert cured with the fixing bolts in position.
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Three inserts were produced : plain face, bunt's name and the tire size
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This shows the mould ready to proceed with the 12 sections needed for the production mould. By changing the silicon insert I was able to produce 2 mould sections for the bunt's sidewall, 2 sections for the tire size and 8 with a plain sidewall.
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The mould sections starting to go together.
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Two more sections to go.........
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The finished mould bolted together.
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400mm of wide tire. It looks and feels like a real tire. If I hadn't been so pushed for time, I would have looked around for some rubber essence so that it smelt like rubber!
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The finished tire showing the sidewall lettering.
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The whole thing is turned over and the process repeated.
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After the rubber has cured, the mould sections can be removed from the tire.
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This image shows both mould halves ready to have the inner skins bolted into position. The rubber is then poured into the void between the mould and inner skin, and the mould halves are bolted together.
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An epoxy laminate skin is laid up to act as a support for the rubber.
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This shows one half completed.
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The tread surface area of each mould is built up with sheet wax to the thickness required for the rubber.
The tire featured on the
'TEN' Anniversary Bike
designed and built by
Streetfighters-Switzerland
Image reproduced by kind permission of
Streetfighters-Switzerland