Now we have built the track to how we wanted it and as big as we can build it, now it came to me that a starting gantry is missing, so I looked on the internet to see what has been done around the world on the full size GP circuit.So once I had a good look around I now had to work out what to build it with my choice was made up by the technique I was going to use, and this would be with brass tubing from K&S from my best stockist Tasma Products. The reason for tubing is because there is sizes that slide in to each other with a good fit, plus brass solders very well.
One of the reasons I did not build it in aluminum tubing was that the biggest size tubing didn't come in 3/8, now to get on with build so next was to sketch out the gantry I wanted to build and work out the sizes, so I can buy the equipment I required, the height was governed by the latest Lap Monitor mad Transponders, as now they receive the signal facing upwards but is still very good side ways as well, the height required to get the full span of the track is 350mm in height to cover 800mm in width, so these were the sizes I had to work with.
As you can see by the drawing it's only rough but it shows my thoughts on how I'm going to connect it together along the top, the other reason behind fixing it in this way was because K&S Tubing is only 36 inches long and I needed a mtr lengths to build this, the amount of cross members of the ladder style side pieces is not to scale as you will see later on. The bases that the gantry sits on is aluminum sheet thin enough so not to cause a problem once slid under the track.
PARTS REQUIRED
3/8 Brass tube
19/32 Brass tube
5/16 Brass tube
1.5mm Aluminum sheet
Square hardwood 9mmx9mm
Tools Required,
Butane Torch burner
thick solder 40/60 grade
Flux pen or liquid flux, Lighter
Hammer, Couple of large clamps
Wire Brush, Centre punch, Marker pen
7.2mm, 2.5mm,5mm drills
QTY + PART NUMBERS
MATERIAL PART NUMBER COST
3/8 Brass tubing
5/16 Brass tubing
19/32 Aluminium
1mm Steel sheet
Now you can see the jig on the bench which all pieces will be made by to keep everything square, and a very easy way of marking each outer tube to drill., you mark the wood jig sides and draw right across so the tubing also gets marked, then find the centres and with a centre punch set on light mark the tubes.
The Cross members are made up with 5/16 inner brass tubes , because I didn't want to drill a to bigger hole because of making the tube to weak, so then I also cut 19/32 Alumimium tube to fit inside to make the size look better to match the up rights and makes the joint look better and stronger. The pen you see me holding is a flux pen which is used after doing a quick brisk brush with a wire brush to clean up the joints, then you add the flux around the joint, soldering was done with a plumbers hand held gas torch and 40/60 this solder.
The trick is once the joint is hot to pull the flame a way from the joint but keep it along the tube , this will keep the heat there to allow the solder to flow, once all the joints are done turn the unit over and do the other side, there might be a bit of excess solder so use the solder very lightly.
If any solder needs removing or adding always put the brass structure back into the jig you have made to keep the shape, and continue to do this until you are satisfied this section is complete.
The picture on the left gives you some of the measurements to build the upright, to start of with the first cross member is marked and drill 70mm from the edge of the 3/8 brass tube then every 60mm then this will give you 6 of the same distance with a little sticking out at the top of the tube. The length of the cross members 5/16 is 61.5mm make plenty of these because there used all over. the total outside width is 80mm wide And the inner aluminum tubing is cut so you get as much length as possible in to the upright tubes on both sides, the tighter the inner tube the stronger the fit. Below is just showing the solder joints and then painted.
Using the same jig, by doing this the shape and size will all be the same and square, you can see the burn marks on the jig from the joints soldered, it would not harm having a water spray bottle at hand in case but I did not have one..
Make two of these in the same jig and then make marks on the wooden jig where you want to put the final cross members and mark with a black marker pen on both units and then dril them out like the other ones I did.
Now the for the bridge part of the gantry, Once again two are required, these are built in the same way as the up rights, and might even be a better idea when build the uprights to make the jig the longest length so the width is them not altered just make the parts you want shorter in the jig. Wish I thought of that when I was building this , you will notice the gaps between the cross members are not the same as the uprights, this of course is up to the builder, but this is how I wanted to do mine, the build technique is the same make on the wood to make sure the cross members are the same on both units. Cut all your cross members brass pieces and aluminum pieces at the same time and make sure at intervals that the units are flat to the floor and then the structure will be total square when finished.
The total length of the bridge rails is 915mm are made just like the uprights the only difference is the gaps between the cross members, and these are 60mm in from one end then 178mm followed by 160mm,115mm,180mm,160mm and finishing with 60mm, but of coarse the gaps can be any you want these are just what i did.
Now you may ask why the big gaps, well these are the top and bottom parts of the bridge, and the the larger gaps are for putting the electronics in and lipo battery.
The picture on the left shows the inner brass cross members being laid ready in to place you will notice marks on the hardwood, these are were the dot punch and drill holes will go. Don't forget to do both top and bottoms for fitting the cross members. when fitting the cross members in to the two rails is when the fun begins.
Now if you look to the picture on the right you will see two small inner tubes soldered to the upright, and if you look closely you will see that the outer tubes have not been fitted , they have not been forgotten , its done for adjustment and to get the complete gantry square.
Firstly what is required is all four holes for the inner tube to be drilled, and you will see that this is done just above the cross member. please still drill these holes in the jig to save any bending in the upright, before making the holes what I would suggest is put a spare bit of inner tube inside to stop the tip of the end of the pipe folding as this is the weakest point at the moment. then drill the holes but start of with a small drill and work you way up to the correct size.
You will also see the lower two holes that need drilling marked out in black pen, leave these for the moment as our main objective is to get the gantry square before any soldering, ok now all top four holes are now drilled , slide some of the inner tubing into the bridge till it buts up as far as it can go against the the bridge's cross member then pull back 10mm and mark the inner tube where the bridge's outer tube stops, and do this to all four ends. Now with all four inner tubes fitted and marked keep the inners inside the outer tubes of the bridge and now assemble the uprights to the bridge by sliding the uprights on to the inner tubes, Now for the trick bit and the most critical part of the build and that is to square the complete gantry up before soldering, this is done by using a set squares and more than one if possible as you first need to get the uprights square to the table at both ends.
Then once you hare sure that you have one upright totally square to the bridge and make sure you have enough passing through the upright hole, now make sure where you are about to solder is clean , then flux the joint all the way around and light up the gas torch put the first part of the heat direct to the joint then slide the heat along the tube so to keep a moderate heat there at all times and then add the solder, if to hot the solder will just fall of , if correct the solder will run around the joint and little at a time not to much at one go other wise it will start to blob and fall of.
Once you have soldered all top four ends and are happyyou can ten cut of the extra that is sticking out and smooth it with a file, then measure the gap between the outer tube of the bridge to the upright and cut them to size with some spare 3/8 brass tubing and slide them on to the inners that are now soldered. And flux the upright end and solder the outers to the inners and the upright, and do this to all top two at both ends , now you do not need to worry about the correct width of the gantry because the top spacers you have just soldered control this now.
