TOPIC:

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...

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...

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...

Those gears looks very similar to the Lunchbx gears..

caprinut wrote:

Those gears looks very similar to the Lunchbx gears..

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...

Hmm, a thought...

Since they are similar to Lunchbox, but smaller.
Could these be a alternative choise for Big Bear? Modded ofcourse..

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...

caprinut wrote:

Hmm, a thought...

Since they are similar to Lunchbox, but smaller.
Could these be a alternative choise for Big Bear? Modded ofcourse..

I think I already look at this : this would require to redesign the gearbox as the number of tooth is not the same. It's probably easier to start from a Lunchbox and extend the wheelbase, but I could not decently call this a Big Bear

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...