About this Blog

This is about the combination of two interests, Radio Control vehicles and Science Fiction models. Its also about vehicle design. The models have to satisfy two main precepts.

1. The vehicles have to work, ie be driveable, but not nescessarily win any races or rock crawling competitions.

2. The main thing is that they have to look cool.

Sunday, 18 February 2018

Reverse Trike part 3

I've been continuing on with the trike project and have completed the construction of the exterior bodywork and added a rear mudguard,



The mudguard is made from 2mm foamed pvc sheet formed around a large diameter pvc pipe using a gentle application of a heat gun. The edges were doubled with strips of 2mm pvc and sanded round. The black bits are some 1mm styrene sheet superglued on with the aid roughing up the mating surfaces with coarse sandpaper.

The mudguard is held on to the swing arm by a bracket made from some aluminium angle cut and filed to shape and pop riveted to the top of the arm. The pvc mudguard is attached with three m3 cap screws  and lock-nuts with a washer on the inside bearing against the soft-ish pvc.


To protect the motor wires which are pretty exposed on the side of the swing arm I made a little guard from some pvc pipe and sheet superglued together in the usual fashion. It is reinforced with a fillet made from a hefty application of baking soda and thin superglue. This may still prove to be too fragile and something more robust will have to be made up. At the moment it is being temporarily held in place with double sided tape. I am thinking of using some double sided foam tape to affix it permanently once the swing arm is painted.



Because this is a sci fi model, it received the customary (perhaps even compulsory) kit part detailing, in this case on the rear wall.


Most of this is tucked away in between the body and the rear mudguard. The radiator like shape is a chopped up part of the top of the wing of a Klingon bird of prey model kit, which I got in an ice-cream container of parts I was given by a very generous donor. The red piping is some single core insulated copper wire fixed with a couple of drops of thin super-glue.




The nose also got a kit part and two buttons from an old computer keyboard.
 


A little inset panel on the sides had a couple of kit parts that could look like recharge hatches. Some evergreen siding adorns the sides and roof where an air vent was made up and added along with a small flat dome kit part.




 I have also made a start on the interior with some panels to help hide all the RC electronics and a small instrument panel steering wheel console.




 The front tyres are a bit of a curiosity. They are Schumacher grass racing 2.2 inch truck tyres. I acquired them many years ago when I bough an old Losi truck from a guy from the UK when I used to race trucks very briefly in the mid nineties. They are never seen in Australia as here offroad racing is more usually held on clay or brick dust tracks. They are made from very hard rubber. As usual they've been sitting around in a box since then and they fit these Proline Agitator Chrome 2.2" wheels Ive also had for years which are molded to take bearings rather than a hex for the front end of a 2WD Jato.

 
All I've got to do now is finish the interior and then it's on to paint.

 

More soon...

Saturday, 10 February 2018

Reverse Trike Part 2

Ive been beavering away on this project a little bit every day consequently there has been some progress on the body.

I started to construct the part of body where it meets the chassis. Using cardboard I made up some templates that closely fit around the Jato chassis and then cut the final shapes in more 2mm Foamalux (Foamed PVC sheet). Whilst the body was in position on the chassis I made up small gussets that linked the bottom sheet to the rest of the body and then proceeded to add doublers to all the edges to give a larger surface area for gluing on the lower sides. The supporting edges were then sanded with a sanding stick with 80 grit wet and dry, to the correct profile. Cardboard was once again employed to rough out the curved shapes required and transferred to the pvc sheet with a generous allowance to counter slippage while super gluing and then sanded back flush to finish.




I then made up some front mudguards in much the same way, leaving lots of extra material to be shaped once the glue has set which isn't very long using a spray of superglue accelerator. The foamed PVC can be coaxed into bends by hand and also by the judicious application of a hot air gun. The mudguard panels were kept level whilst gluing by clamping them to a piece of wood across the front.



Next I cut out a template out of 1mm styrene to scribe around the door opening shape using a scriber. The foamed PVC sheet takes indentation well and it leaves a permanent groove. I used the same template to scribe an outline for the side door window openings. I first used a large step drill to make some large holes in the windows near the corners (step drills tear through this material like crazy), then using my trusty olfa snapper knife joined the holes carefully punching out the rough opening.


 The windows having been sanded to the final outline were filled in with thin sheet polycarbonate after first roughing the gluing surfaces with coarse sandpaper to enable the superglue to bite. To get the radii of the window openings clean and accurate I have a few bits of dowel of different diameters with sandpaper stuck around the circumference with double sided tape to use as round sanding sticks.
In the picture below you can also see a couple of semi circular cutouts in the mudguards for clearance where the front shocks pass through.





 I moved the driver figure forward as he was too far back once the windows were cut. His rear mounting post had to be moved and a little plate made for the front post to meet the screw hole in the figure. I then added a bulkhead in the body behind him.






This is where I am at so far and I feel it is coming together well. My motivation to keep on with it is high so I am hoping to carry this project through to completion...

More soon...

Tuesday, 6 February 2018

Reverse Trike Part 1

I have at least 11, if not more, unfinished projects piling up in my shed. A few of them are so very close to being completed. The sensible thing to do would be to finish the nearly done ones off. What a good idea, I'll make it a new years resolution to not start anything new until I have finished at least two of the existing projects...

I started a new project...

I have been playing a little hill climbing style game on my phone called Prime Peaks. One of the vehicles I took a liking to in the game is called the Pealing Pea, it's a little reverse trike. I thought it might be fun to try and make an RC version some day and then I remembered I have a Traxxas Jato chassis with an almost complete set of front end parts lying around in a box, which may be able to be modded to work. I also have a pair of Imex Jumbo maxx Claw Dawgs wheels and tyres, one of which would make a cool big single rear wheel, and I also have a spare 540 motor with gear box sitting around as well.

Here is the first incarnation of the concept I put a couple of those weirdly scaled wrestler figures in some Axial Wraith seats to see how they fit.



I went with a single arm rear suspension made from some rectangular section aluminium. I  hack-sawed and filed a couple of 60 degree v slots along the length and bent the dog leg shape shown. The joins were brazed together with aluminium brazing rod and a propane torch.
The rear shock is a Traxxas GTR shock from a Slayer or Revo or Summit with a Slayer grade spring.
The arm pivots on an 8mm aluminium pin using a couple of 8x16 flanged bearings in the arm itself.
The mount is a piece of aluminium channel with another ali plate brazed on for the shock tower. I drilled a range of holes for shock placement but those GTR shocks are pretty stiff so I found the bottom hole worked best to balance with the front shocks which are stock Jato shocks, the same size as the rear shock just made from plastic. That's one of the things I like about using Traxxas parts for my creations is that the parts interchange fairly easily between models.



The motor mounts in a radius cut at the end of the arm and is held on with a chopped up hose clamp arrangement. It looks a bit crude but it works. The motor/gearbox combo is rated at 500rpm at 12 volts. It is not particularly heavy duty and after a little test drive all the gearbox retaining screws were found to be loose, I've since locktighted them all. It has only got a plain bearing (not ball) and I am sure it is not designed to take such an axial load, not to mention the hammering it will get if thrashed over jumps an off road tracks. However its what Ive got and it was cheap, only around $15.00 on ebay from China. I am pretty keen on this concept of a motor per wheel, I wish I could find something more robust and flatter that would fit inside the wheel but I suspect that even if such a beast exists it would be way out of my budget.



I came to the conclusion that those pesky wrestler figures just looked too small and the two of them didn't leave enough room for all the electronics and a battery that have to be crammed in there somewhere. So I ditched them in favour of a Tamiya driver figure that I calculate to be 1/8th scale.



As part of the re-arrangement of the driver I decided to flip the side the rear arm was facing. The weight of the motor and gear box tend to roll the vehicle to the side they are on so I thought to counteract that by placing the battery on the opposite side to them. The Jato chassis is asymmetrical in that one side is wider than the other, it is a gas powered car and the widest side is supposed to house the tuned pipe muffler, this is where the battery fitted the best so the arm had to be flipped, all the holes for the hose clamp and shock attachment redone. It wasn't fun flipping the arm, it is quite fiddly to remove and re-insert the pivot pin cause there are a couple of thin spacers made from a thin slice of brass tube that have to line up with the bearings so the pin will go through...aargh. It was a frustrating exercise but worth it as the trike now sits level instead of leaning to the motor side.



The driver figure is held on to a couple of metal standoffs with a couple of M4 screws. Those standoffs are mounted on a PVC false floor I made to give a flat surface to mount everything to. The Jato chassis floor has a lot of lumps and obstructions that got in the way. The false floor is attached to the chassis with 8 M3 counter sunk screws that use a bunch of existing holes that were already in the chassis plus a few extras thrown in for good measure. The underside of the floor is built up from a couple of layers of 3mm and 6mm pvc sheet superglued together. It also blocks some large holes in the Jato blue anodised aluminium chassis. I tried to save some weight but it still ended fairly heavy for what it does,. Grey PVC sheet is a relatively heavy material, but strong and easy to work, it can be drilled tapped, sanded, sawed, heated and bent, takes paint well and superglues extremely well. It cannot however be laser cut as the gases given off will corrode the laser itself and are very toxic.


 

For testing I used a LRP Runner plus Reverse ESC which is for an old school brushed motor. The ESC, reciever and battery are held down by self adhesive velcro, the standard i use is hooks to chassis and Loops on electronic components.
I cut down the Jato radio tray which locates the steering servo and made a couple of M3 tapped aluminium posts to support the cut end.



Next was the body and I first cut up some cardboard shapes to see how it would all fit before committing to 2mm Foamed PVC sheet. I chose the Foamed PVC sheet as a bit of an experiment to try out the material where before I would have used styrene. The foamed PVC is a bit more flexible than styrene and considerably less brittle though not as surface impact resistant, the surface of the foamed pvc sheet dings easily.






As I mentioned I have done a test drive on 7.4 volts (2S) which is adequate but not particularly fast. It would be pretty quick on a 4S or 14.4 volt battery with a suitable ESC and the motor can take the voltage but I fear the gear box would not be mechanically able to take the extra load for very long. A 3S or 11.1 volts may be the sweet spot for this project but that is a bit further on down the track yet.




More soon...