Featherweight. After NCRSF III, Andrews interest in Battlebots was brought to a peak and he wanted to design and build his own. He chose the design himself and its to be a 6 x 6  wheel drive 30lb wedgebot. It will be powered by two A-Packs driving 4" wheels through 3.66:1 gearing using a 12v NiCad battlepack. He has even built a model of it as you can see in the attached photo. We  have the motors and the wheels now and are currently working out how to connect them them all up cheaply and effectively. It is proving to be a fun learning experiance for both of us. More soon as we hope  to have it ready for the spring NCRSF IV. . Our Featherweight will be designed using Solidworks thanks to their generous offer of a free copy of the CAD software. Contact www.solidworks.com/battlebots for details. My first ever solidworks part. This is an fairly accurate 3D drawing of one of the A Pack motors. You can get the Solidworks file in the Solid Models Section I found Solidworks easy to learn and use. I have  a slight advantage here as CAD is what I do for a living usually on Catia or PRO/E I ordered one 12 tooth and one 44 tooth 5mm pitch - 9mm wide HTD pulleys to trial mount to the wheels and motors. I got them from SDP at www.sdp-si.comThey have 3D files for a lot of their parts and prices  are not too bad. This is my first SolidWorks assembly. I created a sub assembly of the small pulley onto the motor and then a top assembly of the two motor/pulley assemblies back to  back. I had some problems getting everything aligned properly as the manual does not explain this well. The Assembly grows. The wheels were mated to the big pulleys in a sub assembly with four M6 screws and then six of the sub assemblies were added to the tp assembly. It  quite easy to do this once you have worked out how! Added the Vantec 36E to the assembly. You can get the files for the Vantec without the added cover in the Solid Models Section.   I have started designing the chassis around the mechanicals. There will be "tabs" and "slots" in each part so that the chassis will fit together like a kit. As the  chassis develops parts get moved around to suit. This is much cheaper and easier to do at this stage rather than when we have paid for actual parts. I also have created a model of the required 12v NiCad  Battlepack. An friend, John Wettroth, has a small CNC Milling machine and he kindly offered to do the necessary work on the wheels and pulleys. John designs DRO's for Sherline among  other things. The Mill had been designed to cut out pieces of rigid insulation and was dismantled with some parts missing when John bought it. He rebuilt it with Sherline  Milling head etc. and is now ideal for milling plastics and nonferrous metals. He built a jig that allows quick and accurate alignment of the wheels and once setup it only takes a couple of minutes to  machine each wheel. Machining the first side of the wheels. We still need to machine the other sides and then add the mounting hole pattern to match the pulleys. The machining was  required to give a flat surface for the pulleys and their mounting bolts to seat on. John has this really neat CNC rotary table. He was the the designer of the electronic and software for it and it was to prove very handy for drilling the hole patterns  in the wheels and gears. It uses a little battery powered "Calculator" to operate a stepper motor that drives the table. You can choose to move a certain angle or fraction of a circle. We needed a small sleeve to match the bore of the wheels to that of the gears so that they could be mounted together on the table. John machined one up on his Sherline.  That's the DRO he designed for Sherline at the right hand side. Its a neat machine but a little small for bot building in the heavier weights. The rotary table was designed for Sherline mills but our job was to too tall to fit his and the table would not fit on his bigger mill. We solved the problem by making a  baseplate that fitted the mounting holes on the table and had holes that would fit the bigger mill. The table was mounted on the bigger mill. This is a Chinese built machine he got at a sale at Harbor Freight but has a circular post that is not particularly good at  keeping solidly locked. Still its pretty nice for $650 or so. Drilling!  We have the wheel and gears stacked up with a sacrificial wood block. The wood prevents damage to the table if we drill too far. It took hours of set up  to get everything ready but less that a hour to drill all six sets. We decided on three holes per wheel rather than the four in the original design because we could and it'll save the weight of  six M6  screws! The wheels and gears after drilling. We still need to tap the hole M6 and open out the holes in the wheels to match. The small gears will be used on the motors and for  the tensioners (still to be designed!) November 1, 2003 After a break over the summer when we had to concentrate on the other bots to get them ready for the 2003 Robot Assault competition, I have restarted design work on the  Featherweight. One big change decided on after a lot of thought was the move from six wheel drive to four wheel drive. This was done for two reasons, weight was getting very tight (calculated using the Solidworks  volume/weight function) and secondly because it was proving hard to design in the tensioner pulleys so that all the pulleys would have sufficient engagement with the belt. First thing to do was build up the axle assemblies. The wheel will rotate on fixed axles. We will use 3/8" shoulder screws with the shoulder acting as the bearing  surface. Two nylon Flanged bushes will be the bearings as shown. Models for the shoulder screws can be found on www.mcmaster.comwhich saved a bit of design time The pulley fits between the flanged bushes with the hub facing out. Any axial play of the pulley/bushes on the axle will be controlled by adding nylon or teflon spacers. The Wheel and hub were redesigned with the three mounting holes as per the actual parts and assembled together using three M6 low profile hex head screws. Models for the  screws can again be found on McMaster. The top assembly was modified to show the change to 4WD and I also added most of the remaining large components. The power switch is from www.westmarine.com and I'm showing two 3600 NiCad Battlepacks but I think a couple of 2400s would be enough.      December 10, 2003 Going to 4WD simplified the tensioner arrangement. The tensioners each consist of two machined Aluminium parts and a 1/4" Shoulder Screw to mount a 12 tooth idler pulley  as shown. The blocks are held together by a couple of M6 Screws (not shown). The slots in the chassis give a about 12mm travel. In Solidworks assembly mode I was able to draw up a sketch of the belt centreline using the pitch diameters for each of the pulleys. the Measure function was  then used to give a belt length of 748mm at maximum tensioner position. I then ordered the next size down, 740mm, from Sdp/Si. Another function in Solidworks then let me add the belt thickness on either side of the centreline giving me the limits of the belt itself so that I could  check for interferences. Notice the A-Pack mounting bolt hits the tensioner pulley at maximum tension. I resolved this by modifying the spacer plates so that the motor is mounted to it and then the hole  assembly is mounted with flat head screws thus removing problems in this area. In order to support the backs of the heavy motors I have designed a couple of blocks that will be fitted to the top and bottom covers that will act on the bolt  heads on the end plate of the motors. I may instead use threaded rod to hold both motors together as one big assembly but even in this case the blocks would still work on the spacers that would be required  between the two motors. An added complexity is that the cables from the On/Off switch etc. have to be able to pass through this area as well. Almost finished the Design! I have added multiple holes for the M4 flat head screws that will be used to hold the whole thing together and I also found the  "transparency" setting on Solidworks so now the Top and Bottom Lexan panels are see-through. I just put in an order to McMaster for all the shoulder screws, nylon bearings etc. we will need, The Belts are on their way already and I have sent the Solidworks files of the  tensioners and motor spacers to cncbotparts for them to quote.  The Vantec 36E just came back from Vantec where it was getting fixed after damaging it at RA in Xtreme impaX. Next job is to create dxf files of all the chassis panels to get the quotes for  the necessary water cutting. Deadline for getting this bot built is Late February for Motorama, looks like we should make it. December 29, 2003 In between completing the design for the 30lber and working on a new 12lber design to replace Cheep Shot we worked on the wheels and sprockets. This is one of the 3/8" Shoulder screws that will act as axles for the main drive wheels. The pulleys needed to be drilled out to 1/2" so that the matching  nylon bushes could be fitted. This was a trial hole in a scrap chunk of Aluminium. Here one of the shoulder screws can be seen fitted into the hole with its bushes. The bush is a little loose in the hole, probably due to the 1/2 drill I used  being a bit worn. I tried a 12.5mm Bit I had but that hole was too small and although the bush could be pressed in the Shoulder screw was a very tight fit. After drilling out the centres of each Sprocket we then tapped M6 the three wheel mounting holes in each one. Since we we had five sets to do I taught my son  how to do it and helped with a couple. Then we had to drill out the matching holes in the Wheels to give a clearance fit for the M6 screws. Normally a 1/4" drill (6.35mm) is good for this but we  found that due to inaccuracies in the hole patterns we need to use a 9/32" so that all the wheels could be properly centred on the gears. The same process was carried out for the two small sprockets that will be used as tensioners and those and the assembled wheel and sprockets can be seen here. I created a trial drawing and DXF file of the top and bottom panels for sending to the water cut folks to check that it works for them. The local place said it  will save money if I can lay out all the parts (for a given mat'l) in one file so that they can cut it all in one go. I plan to add the parts for the new 12lber to be cut at the same time. January 11, 2004 I laid all the .25" Aluminium parts out in one assembly and positioned about 3mm apart (to allow room for the waterjet itself) and then created a drawing from that  assembly. I did the same for the Lexan top and bottom panels as well. I added the parts for the new 12lber, "Cheepshot 2.0" to get them cut at the same time, hopefully saving money and time. The drawing was laid out 1:1 scale on a A0 sheet and a couple of dimensions were added so that the watercut folks don't make a mistake of scale. It is then saved as a  dxf file which has been sent to a couple of places for quotes. January 12, 2004 A workmate drilled out two small pulleys to fit the non-standard shafts on the A-Packs and then fitted pins to ensure they stay on and don't slip. The pins were positioned in the toothed part of the pulley as there was a lot mone metal here than in the drilled out hubs. The pins were carefully sized so that they  will not affect the belt. Got the first quote back for all the Watercutting of the Aluminium parts, $235 all in which doesn't seem too bad considering the metal alone would be well over $100 from McMaster.  Should get the second quote tomorrow. January 19, 2004