Explorer part 6

Finally after over 5 years this project is finished. Most of that time it was just sitting there, the last time I did any major work on it was 2014. All it needed was a cockpit and a paint job and finally it has both bringing it to a better late than never conclusion.

Part 1, Part 2, Part 3, Part 4, Part 5.

I had always planned for it to have a predominantly NASA white colour scheme and I ended up going for a cream off white colour which was then heavily weathered in the usual way with one exception. This time  after the poo juice and white dry brushing I brushed clay powder over it, getting it to gather on horizontal crevices and then spraying it with iso-propyl alcohol to set it in place. I suspect it could be easily wiped off again but for now it is doing the job imparting a realistic dusty appearance.

 

The lighting is working better than I expected, particularly the cabin interior light coming from the control console. It really lights up the occupants well. I also took some photos at night with all the room lighting out so the figures are just lit from the model's own light.

If you have followed along with this project from the start the main issue has been the weight of the scratch built body. I used a lot of plywood in the structure. Now five years on I would do it differently, choosing foamed pvc sheet or even high impact styrene which can be built a lot lighter and it's easier to prime as there is no grain. The weight gain at the front once the cockpit was added meant I had to add a second extension spring to each side of the suspension arms to hold it up without sagging.

I've got one more model I would like to complete before Supanova, the Reverse Trike. I'm not sure I'm going to make it as I am having some difficulty with the low-tack masking tape ripping the top coat off the primer, which is a new one for me, usually if the tape is going to lift the paint it takes the top coat and primer leaving the bare plastic surface. The other problem is the wet winter weather here at the moment is not conducive to painting at all.

Thanks to all the readers who have stayed with this project from the beginning, its been a marathon.
Thanks for looking, more soon...

Space Truck 8X8 part 1

Fairly typically I have started a new project ( actually quite a few) without completing the old ones. I cant help myself, I do so much thinking about a model over a long period of time that once it is underway my mind starts to wander and think about the next one. A new idea can be sparked by some left over parts from some previous experimentation, or by something seen on various forums. It sometimes takes a while to amass the parts required and come up with concept thumbnails that lead to a design I like, and at other times I get obsessed and I just have to start now.
This one is the latter, the chassis at least came together relatively quickly.
As  the title states it is an 8X8, based mostly on traxass E-maxx parts. I got this idea from looking at this modellers site http://www.krohpit.ru/2012/10/8x8.html

My version is nowhere near as sophisticated and although much simpler mechanically, has not been as straightforward as it looks on first glance.

This is the thumbnail sketch I settled on for the body.

I then did some preliminary modeling to scale in Autodesk Maya to refine the design.

Then using the side view picture I knocked up a full size cad drawing in DraftSight.

I purchased a pile of E-maxx parts off Ebay, some new and some secondhand from a guy who also had some wheels and tyres he wanted to offload cheap. 4 of them were traxxas Summit wheels and tyres. I figured I may as well use these on this model and got 4 more new ones, again from E-bay.

While the wheels themselves are pretty solid ( fake beadlocks) and relatively cheap for their size from the E-bay parts dis-mantlers, the Canyon tyres are extremely thin walled, like a thick rubber glove. In consequence they do hug the terrain well but by all accounts are easily ripped on sharp stones. In this case they will probably do fine, time will tell.
Here is the chassis so far, it is big, bloody big... overall 900mm long. The body will add to this length eventually.

It is powered by a DeWalt brushed 14.4 volt motor via a EVX2 speed controller. The transmission is my usual choice, namely the Summit two speed for that low speed, high torque capability. We will see if this will be enough to move this beast, I have not as yet tested it. The two front sets of wheels are steered.

The transmission speed selection servo is an old mini futaba that I have had for years sitting in a box. I purchased this servo from an aborted movie production in 1987. The movie Total recall was originally being made in Australia, in Sydney by Dino Delaurentis and going to be directed by Bruce Beresford. Then the '87 stock market crash happened and the movie got canned after about 6 months worth of visual effects miniatures had been built. I had some friends who were working on the models for the film, they had a big firesale and I purchased a couple of the incomplete vehicles. One was  a 6 wheeled rig made from Thunder Tiger Silver Fox parts and one was the Tamiya 1/16th RC Leopard tank ( which I stupidly sold many years ago), the servo came as part of these.

The aluminium top plate has had a small recess milled into it to clear the spring lever for the two speed shifter. I don't have a milling machine and only a tiny Emco Unimat3 lathe. For this task I use a Dremel bit that looks like a tiny 3 flute end mill in my small 5 speed drill press and very slowly push the plate around by hand nibbling away at the metal. It is not the most ideal set up but it's all I have. I would dearly love a small milling machine and a bigger lathe but at the moment they are just a bit too far out of reach for my meagre purchasing power. The Unimat 3 which I have had since 1990 is very useful for making links and spacers but cant really handle much larger tasks. I don't even have a 4 jaw chuck to hold square items but its better than trying to file parts mounted in a spinning drill and way better than nothing.

The maxx steering post has had to be slightly modified so the lever comes off at 90 degrees to the original position. It is made from Pvc and is super glued to the servo saver part. I hope it stands up to use. If it doesn't I will have to engineer something stronger. The front most steering arm is slightly longer than the inner one. It has a hole further out from the centre so that the front most steering turns slightly less than the inner. The inner set of front wheels turns on a smaller radius then the outer set so the slightly smaller movement that results should compensate. Note that I did not actually calculate any angular mathematics for all this, thats just not my strong point, I just basically winged it. I am pretty sure however, that this vehicle is going to have a relatively large turning circle.

. The diffs  at each end are Maxx diffs, but the two inner ones are modified Revo diffs. Unlike the Maxx diffs which have a left and a right side, the Revo diffs have a back and front half so it is easy to get a second set of diff cases and bolt two front halves together along with a second pinion gear and bearing. This makes a diff that has an input and an output pinion for attaching to the driveshafts that lead to the transmission at one end and the end diff at the other. There is a little lip on the diff cases that has to be sanded off so they mate flush. Then there is a big job in dremeling out the Maxx diff bulkheads to fit these Revo diffs. This is the hardest part of the conversion. I had to also make some new pvc parts to hold the Revo diffs in the Maxx bulkheads so they don't rotate, much like the  transverse collar that comes with the Maxx diffs. It also helps that the Maxx and Revo diffs have the same ring and pinion gears so the axles all turn at the same speed.
The other catch is that the front diff bulkheads are designed to be mounted angled up for front castor purposes. In this case they are mounted flat and the transverse diff collar holes expect this. I had to make a new PVC block to act as a transverse collar holding the diffs at a corrected angle. Originally I made a large block that bolted to the bottom chassis plate but this ended up fouling the steering bellcranks. The blocks had to be removed and remade to bolt to the top plates. That is why there is a couple of unused countersunk holes in the front bottom chassis plates. It is really a very tight fit around the steering beelcranks with a thick drive shaft running through the middle of it and the locking the diffs in place. It was quite a fiddle to sort out. This is one of those occasions where a milling machine would have been handy. I could have made entirely new bulkheads that alleviate all the problems that adapting existing parts throws up.
You have to remember to alternate the ring gear side of the diffs as you go down the chassis so all the axles turn in the same direction, otherwise if they line up all on the same side some of the axles will be going forward while others are going backwards.

Maxx diff at both ends.

Modded Revo diffs in the middle.

Aluminium brace made up to clear the drive shaft for the inner rear diff.

 Various reinforcement blocks of 10mm Pvc have been made to tie all the bits together.
I am planning to build the body out of PVC foam sheet to try to keep the weight down a bit.
Next to go is the battery and ESC mounting positions, then I can test it out...

Explorer part 4

Some progress has been made on the detailing of the Explorer hull.

The black bits are 1mm styrene sheet. the corner triangles are 2mm styrene and the struts are pvc foam 3mm thickness. You can also see a communications dish made from the dome of a battery led push lamp from the hardware store as well as some 1/48th aircraft carrier service equipment kit parts among others. The probe is made from bits of brass. I think the end was turned up for a model boat navigation lamp. Its been sitting in a box of brass bits for years.

The bottom is a piece of grey pvc secured with a screw to a disc of 2mm styrene which is glued to a pvc tube cut at an angle to match the slope of the hull. This tube is then press fit on to a smaller piece of pvc tube glued to the base made from the upper hull of a Tamiya 1/35 Panzer Kampfwagen II kit.

It can be manually rotated into a new position but is not motorised. It is easily removable to prevent damage while still working on the model. The bright orange stalk is a piece of an air restrictor out of a Nerf blaster... no styrene is wasted.

The rear of the dome is a cast part from a set of molds I made back in 1988. Way back then I stuck a whole pile of  kit parts to some perspex blanks to use up some old silicon mold material thinking they may come in handy one day. The molds have sat in a plastic bag collecting dirt for the last 24 years. I got myself some Barnes Easy Cast which is a 2 part urethane casting material which is a clear, water thin, liquid when mixed and sets in 10 minutes into a white solid which is easily sanded. It is really terrific stuff. Unfortunately the quality of the molds is not the greatest and the silicon is now slightly more brittle than it was 24 years ago, but it does the job. There is a layer of dirt stuck in the surface of the initial batch of parts but the primer should cover that. The second pull comes out clean.

I have also completed wiring in the lighting. There are 2 pairs of $2.00  led torches at the front with 4 10mm  clear white leds. At the rear are 2 pairs of the 10mm leds dipped with 2 coats of Tamiya red clear paint. The head lights are accessable through removable hatches at the top. 

Each pair of torches are wired in series. They originally used 3 AAA batteries. 3 X 1.2 volts is 3.6 volts so the pair require 7.2 volts. The 10mm leds are nominally 3.5 volts each so they too are wired as pairs in series. The lighting is then powered via its own dedicated UBEC from HobbyKing. It puts out 7.2 volts at 3 amps which is more than enough. The Ubec connects into the main dual 7.2 volt 2s batteries which connect in series to make a 4s battery. I made a little deans plug adapter that the UBEC is soldered to from a male and female Deans connector joined together back to back. This is then shrouded with some heat shrink. The adapter plugs between the battery lead and the speed controller.

I also am powering the cpu fan on top of the hull from this UBEC. As you cant really see it spinning and it makes a noise I may disconnect it.

I have also filled in the wheel wells with some 1mm styrene sheet.

Other areas have also recieved some further detailing.

Situated across the other side from the dish is another com package with a whip aerial. The aerial is made from a piece of bicycle brake cable. It should bounce realistically when the vehicle is in motion. The top end has a bit of heat shrink to prevent it unravelling and the bottom has a small fishing swage crimped on. The aerial just press fits in so it can be removed while still working on the model.

The red pipes are made from some single core copper pvc sheathed electrical wire. It is easy to bend, holds its shape and glues easily with a dab of thin super glue, plus it's cheap.

A bit more detailing to go and then some more primer can go on. Plus the cockpit interior has to be built. More soon...

Part 1, Part 2, Part 3, Part 4, Part 5, Part 6.