RC10Talk - The Net's Largest Vintage R/C Community

I think there is no more secret anymore on the fact I love rare, original cars with something special on the technical side...

The Playtron Lynx caught my attention for some reasons at some point, and I was recently lucky to find a NIB (damaged box) at an acceptable price... It's complete, and I did not even know there was a driver figure with it.




Anyway, this was not a kit, but it is still interesting as I'm really curious to see it in practice, as it may be even lighter than a Marui Samurai due to the way the transmission is done (reduced to its very strict minimum, and I'll detail this)...

And since I like to work with variants of the same chassis, I also found a dirty cheap incomplete Doberman (its 2WD variant).


The target of this project will be to have at least one of those two cars running, but with some printed parts. And I'll probably have to find a motor heatsync as it is missing on the Doberman...

Anyway, I've started today, with the Doberman front rim...


I do understand why it is done this way, but in terms of printability, that may not be the best way, which means I'll probably do a variant to ease printability. I did not tore down the rear wheel yet, but I believe it will be even easier to print...

I did not have the time to finish the front wheel yesterday, as it was quite late...

The front 2WD tire is now in.


I also worked out the rear rim, the internal ring used to set the tire in place, and the rear tire (used at the rear of the Doberman, and at both front and rear for the Lynx)...



The 4WD Lynx front rims are slightly different from the rear rims but I'll abord this once I deal with the Lynx in CAD. The frst target is to work the Doberman out in CAD...

Alright, the show is starting

Only used a screw driver and a blade to tore down this car...


Few notes :
- There is one dimension of tapping screws, and one of machined screws. My assumption is that it was thought to be quite streamlined in terms of build to reduce the cost. There is not many screws either.
- Front knuckles pivots are build quite similarly to what you can find on a Samurai. The ball cups are fixed together in the arm by a e-clip.
- Rear arms are quite similar to what you can find on a Aristocraft Kangaroo and Dolphin, with a shorter shock arm. The way the arm is set in place is really similar to the Samurai and those cars
- The content of the gearbox looks at first sight oversized... Maybe they just used what they were used to use on 1/8 GP cars

Without wheels, electronics and motor, I measured the weight at 560g. I'll have to weight the Lynx, but I bet it would be quite lighter than the Samurai...

That's a car i have never seen or heard about.
The chassis skeleton reminds me of a Tamiya Frog/Monsterbeetle.

One type of screws, sounds like a dream .

Have fun 3D modeling, will you draw the full car, or only the broken parts?

Mango wrote: ↑Wed Jun 05, 2024 2:06 pm That's a car i have never seen or heard about.
The chassis skeleton reminds me of a Tamiya Frog/Monsterbeetle.

One type of screws, sounds like a dream .

Have fun 3D modeling, will you draw the full car, or only the broken parts?

I guess you did not look yet at any of my other threads
There is not much broken, but my target is to model the whole car. And the benefit from this is that I will be in situation to run a car without any fear to break it...

Time to enjoy vacations, so I can work in CAD again...

Started to work out the transmission parts of the Doberman (I'll add the elements for the Lynx later on).
First the spur gear. Module is 0.8. 20T-55T. This is pretty easy. The shaft has a D cut, which is likely used to transmit power from the gear to a bevel gear to entertain the front part of the transmission...


The Main diff gear is 60T, still module .8


Now comes the difficult part : the bevel gears... The mod seems to be something like 1.6 as per the tooth profiles...


I'll start with the assumption they are 1.6 mod for a start and we'll see...

Do you have any Tamiya Grasshopper / Hornet / Pumpkin / Lunchbox differential gears to compare with? Those look very similar.

Frankentruck wrote: ↑Thu Aug 01, 2024 12:07 pm Do you have any Tamiya Grasshopper / Hornet / Pumpkin / Lunchbox differential gears to compare with? Those look very similar.

Yes, it looks like, specifically for the hex driver and overall aspect... But the bevel gear are not having the same number of tooth (10T/18T here) and they are in smaller mod. And the overall dimension is also smaller, while in proportion it may look similar...

I still had a doubt regarding the mod of those bevel gears...


With a module of 1.6, the cone should be shorter than what it is with the parts. With a module of 1.8, the cone distance seems spot on. Let's go for a mod of 1.8


Now that we have a part designed, I decided to print it quickly to check if my assumption of the module is right... The part is printed in black PETG as I do have a engineering plate and I wanted to launch the print without touching the printer from my desk while looking at the olympics at the same time...


It looks to be right...


And it meshes perfectly...


Time to do work out the big bevel gears...

Later, I worked out the bigger bevel gear... Once the mod is known, there is no more doubts, and you just have to do the proper projection on the cone.


Again, I printed a part (Black PETG)...


And again, it is perfectly meshing with the original parts...


I will have to look at the rear gearbox output to the central shaft, and as well to the front gearbox at some point, but for the time being, I just need to add a pinion, out drives and dogbones and I have the 2WD transmission parts...

I got the diff ready for next steps...


Then I focused on the rather simple gearbox. The left side first...



Once this was done, I did the right side... Which includes fixation for the 4WD variant power output...



Once that was done, it was time to do some assembly...



I still have to do the motor pinion, but I have no clue what was on the Doberman initially, as it came incomplete. I will have to dig in the details once I open the Lynx...

Nice work as usual Mark .
Every time I read the thread title my mind goes to "Lets twist again "
Lets cad again , like we did last summer
Lets cad again like we did last year.
Do you remember when you could buy these parts
Lets cad again , cadding time is here .

Dadio wrote: ↑Sun Aug 04, 2024 11:32 am Nice work as usual Mark .
Every time I read the thread title my mind goes to "Lets twist again "
Lets cad again , like we did last summer
Lets cad again like we did last year.
Do you remember when you could buy these parts
Lets cad again , cadding time is here .

Great one! I have the music in my head while reading it !

The chassis of the Playtron is a space frame. There is two (almost) symetric sides. I decided to start by the right side and to derive the left from there...

The bottom and the rear are used as reference points...


Then we add the rest progressively...


I may not have done it in an optimal manner, but here is the right side...


Then I made a symetry, and played "find the errors" to correct them (left side was 3 minutes of work)


The key chassis part is done, there is still a lot of parts to deal with... But it is a good start...