Yonezawa Datsun

[Nikko85]

Another evening, another piece of RC Japanese Toy Grade history. Following the surprising success of my 1977 Nikko build I thought I'd try another vintage RC car, the Yonezewa Datsun from 1981. I know these aren't Tamiya, but they represent a golden age of RC, and hopefully someone might find it interesting.

I picked up a broken pair on Ebay with the hope of getting at least one working model. I want modern electronics, so the fact there is no transmitter is not an issue. With the price I paid even if I just get a pair of cool bodies to go on something else (MF01x, GF01 etc.) then it wouldn't be a bad deal, but hopefully I can get something that actually goes.

I say I hope I can get something working, as outside of one grainy video on Youtube I've not seen any photos of videos of the insides of this truck, so I've no idea how possible it will be. Some toy grade RCs are trivial to convert, others can be much trickier. 

One complication here is that the car has a 2WD / 4WD system. Although none of the literature says so, it's also got high and low gears as part of this. 4WD mode uses both sets of wheels on low gear with a locked differential at the front and open at the rear, for nice crawling action. When you hit high gear the gear selector mechanism moves the gear at the back to high, but also turns off the front motor and also pulls apart the spur and pinion at the front, which in turns opens the diff. So you have a low geared 4WD system, with a RWD high gear with open diffs, utter genius. To do this the high/low gear selector sits as part of an electrical switch, which tells the PCB to turn off the front motor. It's quite impressive that in 1981 you had features that would still be selling points today (until Traxxas patents them, of course...)

You can see here how the gear shift lever runs pretty much the length of the car, running under the PCB.

 

Here you can see the rear gearbox. A few things to note: The gears are really thin, so this is not going to want lots of power. The motors are also strange, they don't have positive and negative tabs - the entire motor is split in two, one half positive, the other negative. I've never seen that before. The good news is the motors both travel in the same direction which takes away timing issues. An open diff is present. Everything spins freely.

The front gearbox is even more interesting. The spur gear moves back and forth along the pinion. In "on" position it engages with both white and black gears, locking the diff. As the spur gear is pushed back it stops engaging the gears, allowing wheels to spin independently - amazing! 

 

 

So, what's the plan? Well, I want to try and get this running using modern grade electronics if possible.

For the gear selection, at the time this was done with a lever you'd push manually, but I'm hopefully I can get a servo on the 3rd channel doing this - so I can change on the fly. Moving a level which stretches to both gearboxes whilst also triggering a switch to turn off the front motor might be tricky. I will also have to route the front motor to the switch, which will mean lots of wiring.

I will probably keep the original motors, although perhaps a 280 could fit with a small motor plate, but it looks doubtful, and might not be that more powerful. Plus I really don't want lots of power through this, it doesn't weigh much, so hopefully it won't need much.

The steering servo looks pretty simple at least.

If I can get it working I'll work on tires and body. The tires are quite dry, although not cracked, so I may try the WD40 trick, if anyone has actually tried that?

As for the body, it's getting the red/white/blue classis nissan livery, as a vintage Rodger Mears style off roader! 

I may 3D print a new grill and lights to make it a little more classic looking. I will also remove the light and horn, and add some sort of roll bar and spare tire on the rear. 

Although this is going to be a runner, I'm really not looking at a performance vehicle (it's 43 years old, it has zero suspension etc.) but I hope I can bring a piece of RC history to life! Wish me luck.

 

[OoALEJOoO]

Very cool and thanks for sharing. I always love your builds!

[Nikko85]

10 hours ago, OoALEJOoO said:

Very cool and thanks for sharing. I always love your builds!

Many thanks. I really like things like this which need a little thinking outside the box.

I've realised rather than a switch to turn off the motor I could use a spring and battery connector from the original battery connections to make a simple contact switch, attached to the lever.

I have ordered two small metal geared servos for the truck, one for the gear change and one for the steering, you don't need full size modern 1/10 servos for trucks of this size.

These are due to arrive tomorrow, so I will have an explore of how they can connect up. 

[Mouc-RC]

Indeed one more nice thread

Love to see how engineers of these ancient times had the "design to cost" in mind already (maybe more than today, in fact).

Sure you'll do something nice with it! Am I totally wrong to write that iit's a bit like the "Nikko Toyota HiLux 4WD Pick-Up", chassis wise, at least ?

 

[markbt73]

That's really cool! I've seen those trucks before, I think they were sold by Radio Shack or Sears here in the US, but I had no idea they were so sophisticated. It doesn't look like it would be too hard to connect a servo to that long shift lever. And with modern batteries and whatnot, why worry about switching off the front motor in 2WD mode? Just let it run when it's not in use.

[JimBear]

I have never seen such a crammed PCB ... sorting that one out would take a good while I guess!

I really enjoy your builds - looking forward to seeing where you go with this.

[Nikko85]

14 hours ago, markbt73 said:

That's really cool! I've seen those trucks before, I think they were sold by Radio Shack or Sears here in the US, but I had no idea they were so sophisticated. It doesn't look like it would be too hard to connect a servo to that long shift lever. And with modern batteries and whatnot, why worry about switching off the front motor in 2WD mode? Just let it run when it's not in use.

In terms of total performance you are probably right, although I not sure of it's great to keep motors running with zero load. Also there might also be something to be said for engaging gears before motor turns on, given how thin the front gears are. 

When the servos turn up I will have a play. For other electronics I am hoping a HW1060 or carson 70 amp drag will provide enough power for the two motors parallel.

 

 

 

[Nikko85]

1 hour ago, JimBear said:

I have never seen such a crammed PCB ... sorting that one out would take a good while I guess!

I really enjoy your builds - looking forward to seeing where you go with this.

Many thanks - I try and get these cheaper but more interesting cars as as they are not "hobby grade" they are never fixed, so a part breaks in 1985, it's put back in the loft and is still pristine 38 years later (unlike me...)

When I started this hobby there was lockdown, no toddler and work was less stressful, so I could actually drive quite a lot. These days I mainly fix and make as I've just a little time in the evening. I've got one car (CW01 Pumpkin) that is pretty much stock apart from a few upgrades, but I find that the problem solving and engineering is where I have the most fun with the hobby, so it's getting bodies to work on different cars or getting these toy grade cars to hobby grade electronic standards that I really enjoy.

I'll never spend 3 hours masking, it's just not in my nature to be neat and meticulous, but I can spend 3 hours sorting out how to get a steering linkage to work.

 

[JimBear]

Partly thanks to you, I've started to see a different angle to the hobby - that our electronic scrapyard at home is actually worth exploring, not only being a source of parental exasperation (all the money spent on stuff that is now broken). Even when I am not able to actually get hands-on, my head is still at work trying out ideas.

Buying stuff is fine, but thinking with a screwdriver in my hand is what got me back into the hobby again.

[Nikko85]

3 hours ago, JimBear said:

 

Buying stuff is fine, but thinking with a screwdriver in my hand is what got me back into the hobby again.

Thinking with a screwdriver in hand is a great way of explaining it. Time can just disappear as you tinker, think and problem solve.

 

[Nikko85]

Well, this problem wasn't a screwdriver problem, but a 3D printer problem. However I think I spent around an hour last night not really doing anything, but just holding various servos to try and see how the steering might be fixed.

The stock steering is odd. In order to have enough space for the front motor and gearbox they have put some of the steering mechanism outside.

The steering rack moves back and forth as the steering horn rotates, but both rack and horn are on the outsides of the car. I spent a lot of time working out how to make this work, when I realised I could mount a small servo upside down which connects directly to the horn. 

The current horn won't attach to a servo, so I 3D printed a new horn with a 15T spline for the small scale servo I am using. This does mean there is no servo saver, but I am hopeful that the small scale, low speed and metal gears will mean that won't be an issue. It's likely the spline may fail before the servo does, so I might have to think of the horns as semi-disposable.

here are the horns, you can see how the horn is made of super basic shapes that then are blended together. I did use an STL of the 15T spline to add, as that was beyond me. I will test this evening.

[Nikko85]

Well the test was conclusive and they conclusively failed. The spines are just too fine for the printed horns, and they quickly just rounded. 

...so I had to come up with another solution. The trickiness is that front gearbox and gear lever really limit space.

In the end I used the space where the 9V battery would have fit. I flipped a small servo upside down and then made a link to the steering mechanism cutting out a space for the servo and the arm to travel through.

I spent a lot of time cutting them neatly, although it can't be seen with the body on, I want it to look like it's come from the factory.

Installed. The servo is attached with a sticky foam pad then locked in place.

And then from the other side. The arm just fits through.

A M4 nut then goes over the white link, locking it in place. I had to fabricate the white link from plasticard.

It works perfectly. Full steering lock and very balanced. The metal geared mini servo should be more than enough to turn these wheels.

You can also see a second servo which pushes the gear selector. The servo wedged right in place between a post for the PCB and the battery tray. 

On the open setting it is pulled away from the gear lever which is pulled in place with a spring.

When turned on the servo pushes the gear into the second setting.

A wheel is on the end of the servo, to ensure smooth transit as it moves along the gear. And it looks cool.

The only time the lever is forced is when it is disengaging a gear. All the motion for engaging gears is done via springs, which stops the gears getting damaged. 

So now I have to wire up the two motors and fit a circuit breaker / push switch on the front motor so that it only turns on the front motor when the gears are engaged. This will be connected to the lever somehow.

 

 

[Nikko85]

This was my solution, two l brackets with a terminal connection ring on both. One connects to the motor, the other to the esc. When the lever moves in the 4WD position the spring on one contacts the other bracket and the circuit is completed, turning on the motor. 

Works nicely. 

Now I need to fit the battery, sort the electronics and then away we go.

[Nikko85]

Here was my wiring solution. I used  two 16 SWG into a bullet connector crimping them together. This way it's somewhat neat, or at least neater than it could be.

All wired up it looks like this. The wires are a little longer than needed for sure.

And with the li-ion in the battery bay.

I also sprayed the tires in WD40 and left for 8 hours in a sealed bag. They are much much better for this.

Now I can test it. The car is pretty nippy on fast gear. Slow gear slows it right down, and it can crawl ok, although I am a little worried about stripping gears to want to try and power up too much. What is interesting is how dramatically the locked front diff reduces the turning circle.

The gear selector is a little tricky, essentially the gears have to line up for the gears to shift over particularly going into low gear which needs two sets to line up. Manually this was probably done by rolling the car forward and back, but I am finding that sometimes the gears just don't change. It may be I have added too much grease in the gearbox, stopping them slide past. I may also consider the option of beveling the gears  so they can slot in a little more easily. I could also consider a stronger spring as perhaps that has lost tension after 40 years?