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Groomi
12-10-2008, 06:18 PM
Hi All, I'm new here having searched the internet for a forum where people design and build their own r/c cars. Some great projects on here!

Over the next 12 months I'm intending to build a 3-wheel buggy just for the fun of it (and the design has been mulling around in my head for years). I'll be using Schumacher internals from either my Procat or Bosscat and adapting the belt drive to suit the 3-wheel layout.

Why 3 wheels? Well I'm interested to see just how lightweight a buggy can be and following the old Lotus adage 'less is more' it seems worthwhile to look at losing 1 wheel and all the adenda associated with it. I'm hoping some careful design can overcome most of the stability sacrifices, but time will tell!

Although I'm doing this for fun it would be interesting to race it when it's finished to compare to a normal 4-wheel buggy. Would any local level race meets allow such a machine to compete?

Spoolio
12-10-2008, 08:23 PM
...following the old Lotus adage 'less is more'...

Yes, as in "less [time spent building it properly] is more [warranty claims]" :).

However, your project sounds intriguing - post pics when you have some. I assume you'll be going with a trailing wheel layout rather than a leading wheel (Reliant Robin-esque) design and will it be 3WD as well (otherwise I foresee immense traction problems). If you go 3WD you may win all your classes as you'll be the only runner. Probably.

Groomi
12-10-2008, 08:38 PM
Ha ha, no comment on Lotus build quality!

Yep, definately going for 3WD, 2 up front and 1 behind. The intention is to design and build it as a 3WD buggy and then after a bit of fun and development making a follow-up rear drive only tarmac special. As you say, traction will be a problem, but the potential extreme light weight and drag efficiency advantages 'may' make it worth it.

If both cars prove to be hopeless, at least I will have answered the question that's been filling my mind up for years!

Groomi
13-10-2008, 03:52 PM
Thinking a bit more about this last night and decided that I should concentrate on the unique part of the concept (ie. the rear wheel/suspension/transmission assembly) first. So I've decided I'll make a development model first using the entire front end from the Procat and then making a simple chassis which enables the unique rear assembly to be played about with and also give me freedom of packaging the batteries and radio gear to find the best weight distribution.

This model will be the 'proof of concept' before putting more time and effort into a proper version utilising some fancy chassis and body ideas I have, together with a much uprated front end.

Will try and post some sketches up in a few days and will update with (slow) progress.

Mike Hudson
14-10-2008, 11:15 AM
sounds funny but interesting, you should have made it 2 wheels at back and 1 at front like a reliant robin so it rolls when you try a hairpin at speed :lol:

mark christopher
14-10-2008, 12:57 PM
got to look at a rear swinging arm such as a motor bike

Groomi
14-10-2008, 02:12 PM
got to look at a rear swinging arm such as a motor bike

Yep. Going to make sure the pivot point is exactly in line with the pulley centre to ensure the belt tension doesn't change during suspension compression.

This will be the 'fun' part...

twisty
14-10-2008, 04:14 PM
Outfits are an aquired taste,look to full size for a solution with ideas,Grinnall do an interesting 3 wheeler
http://www.grinnallcars.com/content/home/scorpion_III.html
and various people have tried 2 at the front,seems to work best with the rear central anything else with 3 wheels seems to have stability problems and/or tourque steer problems.
Off set 3 wheelers such as bike outfits pull to one side whilst accelerating and pull to the other side whilst braking.
2 or 4 wheels are better than 3 in general IMHO but try to keep going you might find something new.
Good luck.
:)

Groomi
19-10-2008, 11:09 PM
Well I made a very slow start on Friday evening. Having dragged all my old RC stuff down from the loft, I started stripping down the donor car - a CAT XLS (which I always thought was a ProCat, but seems I was wrong).

Then I made a start at learning my way around Solidworks and fully modelled a rear wheel. Hopefully I'll get quicker as I do more, as I intend to model up the entire design so I can work out all the packaging, linkages and fixings before actually butchering any aluminium or carbon fibre.

Just feels good to have finally started doing something towareds making this thing a reality. :)

Spoolio
20-10-2008, 12:56 PM
Yep. Going to make sure the pivot point is exactly in line with the pulley centre to ensure the belt tension doesn't change during suspension compression.

This will be the 'fun' part...

What about an double pulley on the pivot point, one taking the main drive belt from the motor then another short belt from there down to the wheel, that way the belt length and tension will remain constant.

Groomi
20-10-2008, 06:44 PM
What about an double pulley on the pivot point, one taking the main drive belt from the motor then another short belt from there down to the wheel, that way the belt length and tension will remain constant.

That's pretty much what I was thinking. As I'm using the XLS as a donor I'm somewhat constrained by the belt lengths. The short drive belts are too short to give a long enough rear suspension arm, so I'm going to turn the whole thing around and use them at the front, then having the long drivebelt on a very long suspension arm running alongside most of the chassis.

Although this sounds very wierd, it will have the benefit of the actual structural part of the chassis being very short and therefore very stiff. Providing I can make the long suspension arm stiff enough, it could work quite well.

I'll endeavour to get some sketches posted up soon to make the above a bit clearer.