rumdog design

RumDogDesign (CHBE Ltd)

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RumDogDesign is a registered trademark of CHBE Ltd. Providing engineering design services, including piping design, mechanical design. This blog shows a portfolio of 3D modelled products by Colin Bark, with over 25 years experience designing products & systems in various engineering disciplines including oil & gas, aerospace, hermetics, bicycles & shipbuilding. The site will expand to include everything from modular gear mechanisms, pedals, frames, handlebars & brakes, with some new ideas in where 3D printed components can develop in the near future.

If you like my designs or my 3D CAD skills & are currently looking for contractors in engineering design or CAD, so please feel free to view my CV & contact me via email

Adjustable Bicycle Crank

August 9, 2023Leave a comment

This product was developed as part of an Open University final project. The crank can be manually adjusted to the correct length, while maintaining the weight of an industry standard crank such as the Shimano Ultegra. The internal profile has been designed using finite element analysis (FEA) on Inventor Nastran, to allow weight reduction, while maintaining deflection & improving fatigue life of the crank over current commercial products. The externals are shown, internals are subject to further refinement & potential patents.

Bike handlebar mount for GoPro style fitting action camera

December 17, 2018November 30, 2022Leave a comment

Another update on the handlebar GoPro mount, which the initial prototypes proved the function. I’ve updated the parts, the integrated 3D printed hinge works very well, the tensioner required a little increase in size to allow easier manipulation. After tweaking the body, it can now be printed without any support material, with the domed interior being replaced with a cone tangential to the sphere, allowing it to be printed as an overhangwhile retaining most of the surface for tensioning the ball joint.

The product consists of four 3D printed parts, as can be seen on the exploded view below.

Bicycle Action Camera Mount Prototype

December 1, 2018December 12, 2020Leave a comment

*Details coming soon*

This mount has an integral 3D printed hinge for the handlebar attachment, no additional moving parts or fixings required for attachment. The main body itself, the insert & fixing system is also 3D printed. The spherical joint within the main body is integral to the functions of this mount, it allows rotational movement & can be interchanged with other mounting options, for different parts of a bicycle, or even a kayak.

Prototype parts being tested now, more details before the end of the year.

Bicycle Rear Mech #1

March 1, 2016November 30, 2022Leave a comment

RumDogLogoNew1 RearMech_2_blue_logo

(Work In Progress) The primary bicycle component manufacturers have a multitude of rear mechanisms available. Retailers will stock 8, 9, 10 & 11 speed mechs for mountain bikes, road bikes & hybrids. There are often 3 different cage lengths, depending on what size of sprockets you’re using & the movement you require to take up chain slack. What if a modular rear mechanism was available, where you could interchange parts to make it fit any setup, for any manufacturer?

RearMech_2_blue_main

The idea shown has a few minor changes to a standard part, which makes all the difference. The swingarms are removable with an allen key, which means that they can be interchanged with different length ones, allowing you to retain the main parts of your gear mechanism if you upgrade to more sprockets. A different length swingarm will provide different movement for the same cable pull, so with a variety available it will fit every system. This method also allows replacement of single parts if you experience any crash damage. If each component was available in different materials & weight, a slow upgrade could be chosen, starting with he cheapest & upgrading to more expensive materials over time.

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This is a work in progress, there’s no springs or extent adjustment screws in there yet, I’ll do some work to see how many swingarm lengths may be required to cover the majority of setups. It looks like only 3 different cage lengths will cover every option.

RearMech_2_blue_rear

Ti Compact Frame #1

February 29, 2016November 30, 2022Leave a comment

TiBikeAssembly2

A basic Ti frame, my favourite material for ride quality, as a lighter rider I find carbon frames are built for heavier riders & don’t provide enough compliance for our poorly surfaced roads. This frame has ‘compact’ geometry & a lower top tube position than normally found on Ti frames in the marketplace. As with a proportion of riders, my knees tend to cross the top tube, so a high or wide top tube tends to stop me pedalling naturally, have found myself spacing pedals out in order to counter it, this frame design eliminates this need for me. Even worse for ‘top tube brushers’ is the current fashion in carbon frames which have a very wide top tube structure towards the seat tube, possibly designed for a combination of aerodynamics & stiffness, but not ideal for everybody, I find these impossible to ride. Graeme Obree eliminated the top tube altogether for this reason as he had brought his pedals closer together, so any top tube would have caused him problems as his knees also cross the top tube.

I’ll initially be attaching the parts I design to this frame.