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Post by woody on Oct 27, 2009 10:41:02 GMT
Hi , my doodles and ideas in my head may soon become reality , i have ordered my steel ( 1insX1ins 16g) and have got 3 BMX wheels ( yea i know i need at least 4 , but its start) , i have 2 hacksaw blades and have arranged to borrow a small MIG welder I should be able to build one that is strong as i was a panel beater for 30 years and i am now a flight line mechanic (servicing Jets at RAF Valley) i will try and put up a few pics of any progress please feel free to add any advice or tips
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Post by Scottish Cartie Association on Oct 27, 2009 11:45:50 GMT
Hi Woody, There's some information and tips at scottishcarties.org.uk/resources/construction. If you browse around there you'll find loads of links to other sites with some really useful info', plus a few guys who post there who'll be only too happy to answer any questions you might have. Common gotchas on a first build are; * steering too twitchy, leading to the dreaded speed wobble. Pay attention to steering ratio, caster and ackermann angles or you'll feel like you're driving a shopping trolley. * Wheels not mounted securely enough, so they flex or even come adrift when going round corners. Get good strong wheels. If you are stub mounting the wheels, the spindles need to be at least 14mm diameter. Any thinner and they will bend or even snap if they are not mounted in forks. * Track too narrow / CoG too high, making the cartie unstable and tend to roll when cornering at speed. Low and wide is the way to go. Hope that helps. Looking forward to seeing how it turns out. Good luck!
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Post by Scottish Cartie Association on Oct 27, 2009 12:33:44 GMT
... also ...
* make sure you've carefully read the rules of all the events you want to run at. They are all slightly different and if you're not careful you can find your pride and joy is too wide/long/heavy.
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Post by woody on Oct 27, 2009 21:27:29 GMT
Thanks for that , i know it has been said before but it would be good to get some set of specs that would be acceptable nationally , i have been reading the threads on rules being a bit hit and miss , it would be good to have national spec you can use anywhere and maybe local spec for local events , would it be possible to put up somewhere a list of minimum specs that are acceptable nationally?, like there seems to be 2 different maximum lengths so if i make mine to the smaller it will be acceptable to both , same with width and max weight
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Post by Scottish Cartie Association on Oct 28, 2009 0:05:35 GMT
A bit like this, you mean? scottishcarties.org.uk/files/derived%20national%20rules.htmI think you're right that we need to derive a nationally compliant set from the existing rules rather than try to impose one, top down. Almost all the soapbox races in the country are community based events that have grown over the years because of the efforts of hard working volunteers, and I doubt any of them would react well to an organisation coming along to say "we're in charge now and you have to do it this way". I know I wouldn't. The problem with trying to derive a universally compliant set from the various local rules we have at the moment is that the result, as you'll see from the table, is that you end up with really restrictive set of dimensions. For instance, min track 90cm and max width 110cm gives, when you account for a typical bike hub width of 10cm, a track that must be between 90cm and ~100cm. That doesn't leave a lot of room for individuality or flair. It also means you end up needing features that are not needed for most events. For instance, there are only four rule sets that require roll bars, and two of them (UKGSA and Formula Gravity) aren't actually used anywhere as far as I know. I think the way forward is some fairly minor tweaks to a some of the rules so that the derived national rules is realistic and not too restrictive. If we could end up with something close to the following I think it'd be pretty good. Max Weight : 100Kg Max Length : 2500mm Max Width : 1500mm Min track : 700mm Min Wheelbase : 1300 Min wheel diameter : 200mm (?) Min Wheels : 4 Roll bars : Optional Harness : Only allowed if roll cage fitted
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Post by woody on Oct 28, 2009 10:07:43 GMT
That looks good , very similar to the list of specs i have been getting going through various websites , i am going with a roll bar for now ( in this sport spills are inevitable ) , is there any reason for the minimum wheel size ? (i think your website is down at the moment the link wont work)
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Post by Scottish Cartie Association on Oct 28, 2009 12:54:35 GMT
scottishcarties was down briefly earlier this morning, but is up and running again now. I don't know what the reason for the minimum wheel size is - perhaps to disqualify luge and turtle? If so, I think there would be better ways to do that.
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Post by rick on Oct 28, 2009 12:55:18 GMT
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Post by Scottish Cartie Association on Oct 28, 2009 13:14:05 GMT
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Post by rick on Oct 28, 2009 13:19:00 GMT
Is it better to put body work on...What are you guys using for materials.
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Post by Scottish Cartie Association on Oct 28, 2009 13:27:10 GMT
I use leather on my body
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Post by rick on Oct 28, 2009 13:32:45 GMT
LOL !! so if there is no body work on these things you have to wear leathers ??
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Post by Scottish Cartie Association on Oct 28, 2009 13:56:36 GMT
That would generally be the case, yes. It's certainly how we framed the rules for Cairngorm Soapbox Extreme. However, there is no overall acceptance of this yet and most events have slightly different rules. I'm looking forward to discusssing all these issues at Cadwell next month, and I really hope we'll be able to make some progress towards a more rational state of affairs.
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Post by rick on Oct 28, 2009 21:03:24 GMT
Ok, have had a good look at the regs and it seems tha the best wheel for the job are 20" bmx wheels. Was that blue one from Belchford running them? Can you tell me when the races are next year and when the season starts so I have a time scale for the build to work to .....Thanks again for all your help.
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Post by Scottish Cartie Association on Oct 28, 2009 22:24:32 GMT
20" BMX wheels are a common choice 'cos they're strong and easy to source. I think "that blue one" ( Centa Bavaria) was using smaller wheels though - probably closer to 16". (I ought to know exactly as I was in the next pit bay to them at Belchford this year. ) You could ask them yourself though - Andy's contact details are on their web site. As for dates - all the confirmed dates I know about are on the events calendar on ScottishCarties, and I keep that as up to date as I can so you'll be able to check as other dates are confirmed. I expect most of the other events will be similar dates as last year. There are links to the various event web sites on the ScottishCarties links page.
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Post by Scottish Cartie Association on Oct 28, 2009 22:51:35 GMT
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Post by woody on Oct 29, 2009 10:27:50 GMT
That is brilliant , just what is needed , Your "derived" could be the new national guidelines
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Post by Scottish Cartie Association on Oct 29, 2009 10:44:48 GMT
I sincerely hope not - they are way too restrictive! The reason I published them is to illustrate the porblem and show that, with a few changes to some of the rule sets, we could come up with a much more useful set of specs. But we're getting a bit off topic - probably best to continue the discussion on rules here.
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Post by woody on Oct 31, 2009 21:00:35 GMT
Ok , i am watching with interest the "rules" thread with a couple of ideas like telescopic width adjustment , but i wont bother on this one . i picked up my steel yesterday (36m of 1inchX 1inch 16g) and i have built my " outdoor workshop" ( a gazeebo in my back yard ) i am picking up the MIG on monday so i will start cutting and welding soon
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Post by leew on Nov 1, 2009 10:50:53 GMT
I would recommend building a cart with a body, while it is more complex you will almost certinly go faster with a well designed body than without one. My cart goes about 25% faster with the body than without. You can make a decently fast body cheaply and easily from Correx or thin plywood.
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