Monday, 8 May 2017

Thorpy's Grass Track Dilly Cart Build

Thorpy's Grass Track Dilly Cart Build - Intro


This is a brief write up of the dilly cart / box cart that my kids and I have built for the National Trust, Landhydrock, Dilly Cart Race. I am not racing in the kart, instead my wife, and two daughters are entering because I enjoy building things, but not driving.

The race is a grass track race, and as such the rolling resistance is quite high. For this reason the race organisers suggest the use of 24" wheels or bigger.

Normally a box cart, or dilly cart track is paved in some way, and on these tracks a smaller 20" BMX wheel will serve you well, they have more spokes and are generally stronger.

I chose large wheels, because I think it will be annoying if the cart does not roll well. I think my kids will use the brake quite a lot, and not gauge the track ahead very well in terms of the momentum, required. Bigger wheels will reduce the likelihood of stalling on a grass track. So that is why I think the bigger the better even if you are not out to win.

Watch the length. 2.5 meters is soon used up!

Thorpy's Grass Track Dilly Cart Build - Specifications / Rules


For Landhydrock, Dilly Cart Race 2017 the carts have to meet the following requirements, unlike many cart races, you only need 3 wheels, which makes things a lot easier in terms of steering!


  1. Carts must have a minimum of three load bearing wheels.   
  2. We recommend a wheel size minimum of 24 inches, as you will be racing on a grass track.  
  3. Carts must have effective steering. 
  4. Carts must have effective brakes. 
  5. Carts must fit within the following dimensions:  


  •     Maximum length 250cm, 
  •     Maximum width 150cm, 
  •     Minimum track width 60cm 
  •     Maximum weight of vehicle, ballast and driver 150kg. 


  1. Carts must not have any sharp edges, glass or loose parts.   
  2. Carts will be examined before racing, and any carts considered  dangerous or unsuitable for the course will not be allowed to race.   However, inspection does not constitute a warranty of safety.   Drivers are solely responsible for the safe construction and operation  of their vehicles. 

Wonky but Functional



Whilst I found the width allowance to be very generous, you will have the watch you length. The 26" wheels add a lot of length as there are approx 60cm front to back so there is 1.2 meters straight away. The pictured cart is 2.4 meter long approx.

Thorpy's Grass Track Dilly Cart Build - Ingredients


Two bikes will provide moist of the stuff you need, they will have mounts for brakes, wheels, and other handy bits saving time and trouble. To summarise, try to get hold of two old mountain bikes. The recycling centre is a good place to start, where you could get 2 bikes for £20.

To Weld or Not to Weld?


If you buy a welder, then I am pretty sure you will be able to learn to use it pretty quickly. A cheap gasless mig welder can be had on ebay for £120. A welder is such a handy thing to have, by the time you have spent £50 on an alternatives such as epoxy, rivets or bolts etc. then  you may as well make the investment.

If you were to building from wood, that is OK.  I have done this before and the results are not as good. And even then we used some welded parts for brackets etc. I have seen some good wooden carts built with wheel barrow wheels, but with larger wheels it become more difficult.

Extra Tubing

The best source for cheap tubing I have found is electrician's conduit which you can get from any plumbers store or electrician store. Not B&Q, somewhere like plumb-base. It come is 3 meters lengths so unless you have roof rack, take a hacksaw with you.

Seat


You will need something to make the seat, this could be a canvas only deck chair type thing, or as I have done a plyboard jobby with a bit of cushioning (roll matt).

Foot Rest

This could be wood, tubing of net / mesh as used in pictures.

Paint


I used water based exterior paint, with an undercoat. It was left over from our front door. Metal paint would do a better job, but it is very smelly (high VOC content) and I wanted my kids to help paint it.

Tires 

I am just using the tires that came on the bike. But you could opt for fatter tires with a shallow tread if you were really keen.

Ballast

Ballast is a heavy lump of something that you attach to the cart to make is go quicker. Heavier thing have greater momentum, and so speed gained down steeper sections will be maintained through flatter sections.  I am not putting ballast in the cart, I just want my family to have a nice day and I am not bothered about winning. If the dilly cart were to tip over with 25kg or 50kg of ballast in side then I do want a family member underneath that kind of fast moving weight.

Brakes


Hopefully you can use the brake son the bike. A front wheel break is not ideal as there will not be much weight of the front wheel, causing it to skid easily, at which point the steering will stop working! Not ideal.

1 Break on one side of the rear, will cause a little skewed, when braking, but is an ok option, if you have time then brake both rear wheels.

A very simple solution is a ground bearing break. Pull up a handle and a piece of wood hit the ground slowing the cat in the process.

Thorpy's Grass Track Dilly Cart Build - Design


Perhaps this should have come before ingredients. . . . . 

HAVE FUN. Do not worry too much about your design, unless you enjoy that part of it. Just try to keep the wheels aligned, and think about the human that has to fit inside the dilly cart. A good way would be to sit on your garage floor and draw around you required seating area, with a permanent marker. Then build the cart around this. 

Two Bikes Stuck Together make the Job Easier


Make sure the cart is strong enough. I will test out our dilly cart before I put my kids in it. I am double the weight of my wife, so I consider that an adequate test. 

So many things in life are prescriptive, why not just make it up as you go along!

Thorpy's Grass Track Dilly Cart Build - Extra Bits


Some extra bit s that might be considered . . . . . 

  • Flags 
  • Streamers 
  • Roll Bar - Stops youngsters getting squashed.
  • Horn
  • Spokey Dokeys
  • Spoiler
  • Mudguards - Stop debris front front wheel going in eyes.