Designing a high performance sports car - tailgate or boot space and gas struts





JUNE 2015 - Most of our volunteer resources are now going to the SeaVax ocean cleaning project. But every now and again - and to ring the changes - someone has an idea that they just have to try out. The hatchback style tailgate is just one of those tantalising experiments and a good little design exercise for work experience. 



City cars are not renowned for their boot space or other load carrying capacity. But this little gem of a sports car can carry (if loaded carefully) a full shop for a family of four. 


To begin with we didn't want a hatchback, just an opening tail and a support arm - and that would have worked - indeed, that would have made for a lighter and stronger structure. But then we thought about lifting bags over the lip and decided to make it easy for anyone to load a heavy shopping bag, or even mount/dismount a generator. To make it that much more convenient, we then went for traditional gas struts, so that the hatch opens up on its own while you are struggling with two or more bags.


It was a lot easier than with the Gull Wing doors, which had to work on just one gas ram. Mainly because of the limited space and low roofline. With the boot, we can have a balanced system using two gas struts.




AUGUST 2014 - This is what the car looked like in plan view before we changed our minds and opted for a hatchback. Timber is used to make a framework (coachwork) as the foundation for composite panels. There is no boot lid at this point - and the rear panel has not been cut to make the car a hatchback. Much of the timber in this picture will be replaced by carbon fiber, steel, or aluminium, in the final cut.  Please note that these pictures are copyright © BMS 2015 and you will need our permission to reproduce them. We can supply higher quality for magazines, etc.




Working out the best angle and installation points is done by trial and error. Designing in AutoCad is fine, but sometimes an obvious solution presents itself out on the shop floor. It's a simple matter to clamp brackets into various positions to test the theory very quickly. That shown above is not the best solution, but a stage on the way to perfection. We will need to make steel reinforcing brackets. When the hatch boot lid is skinned, it will be far stronger. The corners will be beefed up to spread the loads of 120 lbs of push against a lightweight frame.



Gas spring strut 10mm ball mounting brackets in 3mm steel


Once again we used these standard 10mm ball mounting brackets. We like this design because they are 3mm steel that will allow us to be relatively brutal - if we need to. Note the two different types of gas ram with plastic and steel cup ends. They both work fine, plastic has the advantage of not needing lubrication. Steel is stronger. Take your pick.





LITTLE MARVELS - We take these struts for granted today, but before they were perfected, designing a spring assisted opening was a deal more complicated. A little experimentation is required. When ordering gas struts make sure the stroke when coupled with the full extension 'D' will give you the angle of door opening that you need. Struts are available off the shelf that can lift from 10-100 lbs and more. 


Gas struts for the Ecostar DC50 electric car








UK Government 75 million to build cars of the future

South east local enterprise partnership

Car gas struts UK

Associated Spring Company UK

Gas Springs

SGS Engineering

Telegraph UK finance the electric cars of the future






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