Graupner/Mugen Mercury CAD model...

[silvertriple]

Hello!
During one of the last year vintage events, one guy looked at my cars and he was clearly impressed by the work on the Spirit FF... We had lot of discussions since as he was in one of the clubs I was going for running my cars... One day, he told me : "Marc I have some rare cars you may model at some point". It materialised at some point with boxes with all the parts of a Mugen Mercury. As it is not build, there won't be any picture of a built car in this thread...

Instead, pictures of parts and pictures of the modeled parts... And I won't build the car, as it will go back to the owner once I have finished the model...

I had a look at the parts, and it is clearly part of the complex ones . And that is good, because I love the difficult things...

But I decided to start simple...



Or not so simple in fact, as for the rim, I did 3 bodies, made cuts in 2 of them separately before assembling the whole stuff..


After the rim, I did the tire...


And here we have the complete wheel...


And another project is starting...

[silvertriple]

Time to deal with the motor plate...

Here is the motor plate. I don't even know how it was mounted, as the car is in parts...



Once done, I launched a quick print to check for accuracy (things I was not doing in the past as it was the best way to stop working and focus on fixing the printer )...



One advise for those doing like this : having plates onto each other is not enough to check measurements are right...
The real test is the screw test : if they are not parallel, there is something wrong...
3 measure out of place of a quarter of millimeter...


Corrected now. we can move to next part...

[silvertriple]

After the motor plate, I decided to tackle the arms...


Front first (right one)...


Firstly, it is not easy to measure. As ususal, I start by an observation round to check if what I see parallel is actually parallel. Then, I set the plan.

There is a part which is simple (with the triangles)...


Then some suppressions to make the attachements on both ends


After this two bodies and holes to add and finally a removal to give room to the transmission...


I will do the rear one tomorrow, but the design of those parts already appear complex...

[silvertriple]

Rear right arm is done following the same principle as front arm, but measurements are even harder...




And we have our suspension arms, now (left side will be mrrored).

[silvertriple]

Next is about front spindle, front and rear carriers


Had a quick look at the manual to check. The car has 2 left spindles. The owner knows it and highlighted it to me. I decided to make the left and get it mirrored for the right...


The spindle is composed of 2 bodies with an angle of 10 degrees between them...




Once assemble only to do the two bottom holes and we are there... That is almost easy

Then we just have to create a joint to position the part...


Next is the front carrirer... The part is easier to do, there is not a single subtility about it... That's no fun




And a joint...


Next is the rear carrier... A bit more complex than the front carrier. I did use 3 bodies to build it (forgot to takes screenshots, I let you guess )


And here is the part in place...



I'm not sure what I do next... I may take benefit of the sun outside to do a bit of paint...

[silvertriple]

WHile awaiting the part for other projects, I restarted to work on this Mugen Mercury...


The chassis is quite complex to measure for multiple reasons : it has everything to make it difficult :
- plans are not parallel
- length is too long for my caliper
- and each curve in the plan is not clear, as it is a fillet

In other words, business as usual... I started to establish the base profile and the full length, and tried to reproduce the slopes...


Once this was done, I started to make some extrusions, and next I put the motor plate in position (not on the right side of chassis because I started by the right side) to establish the position of some of the holes...


One of the reason I procrastinated a lot was that I did not thought the plan. It's the case now, so I should be able to move forward...

[silvertriple]

An opportunity for a cheap chassis last week I discuss myself about taking it or not for a few day, and finally decided to get it... It was not really expensive anyway, and althought there is some damage on it, I know that I can find what is required to make this a great car at the end, and further, I already know that I should be able to do all the missing parts (as I still have the Mercury of my friend Pascal in parts until I finish the CAD model).



The format of this chassis is even more impressive in hand. It's weird, it has very wide track (I don't think it was the norm when it was out on the market), and the suspension travels are huge... And the bumper is positionned in a way that whatever angle the car would arrive from a jump, wheels would be first on the ground... This is slightly too modern car for my taste, but I will have to get it ran at some point, just for the sake of knowing how it works...

[silvertriple]

I have 2 Mercury at home currently. The one from my friend and mine. Both have deformations in the chassis, making the measurement difficult. There is still some new parts available somewhere in France, and even at reasonnable prices. I decided to order a chassis, and few other additional parts... They arrived yesterday.


That should allow me to work this out more easily. Unfortunately, no shocks. I will try to find some at some point.

I decided to open and model a diff this morning.

First removing the e-clips and ball bearings


Then, 4 screws and it's in parts


The center part is a bit complex...

It will require to identify the number of tooth of each gear, the module. And from this, center will be defined by the geometry, and by gears center distance...

No difficulties for the gear with the plugin inside Fusion 360, they are in module .5 (metric) and the number of tooth is 14 for the outputs and 10 for the two internal gears... I took note of the interdistance between 10-10, and 10-14 and draw a sketch to start to work out the center part of the diff...


The other side is using a similar drawing but is moved as the two internal gears are working togther in the center... Once this piece is done, the other parts are super easy.


It's actually very difficult to show... But I tried to do something



The center piece is also including a side for the belt. MXL025 format, like on the 44B chassis, 37T around the diff.


Once there, I added the ball bearings, the pins, the outdiff and the eclips, and my diff is built (and the real one rebuilt )


Front and rear diffs are the same, they are just inversed. That is also saying there is two belts, and I will also need to see the center diff. But that will be for later...

[silvertriple]

After the diff assembly, there was an easy part sitting on the desk...


The diffs are mounted in excentrics, and those are used to set the belt tension.


After that, I started to look at the shock towers.


They are obviously highly complex. It requires boolean, and the geometry will be difficult to work out... I made a quick draft for the front shock tower (right side), and I can already tell there will be a second attempt.


This is the type of parts you need to do assumptions about the things. And you have to check at the end the assumptions made about the geometry are right. And in that case, I definitely need to review some of the initial assumptions. In short, the part is not complete, and I'll probably have to redo it from scratch (and it's also probable that I do the same for the chassis halves)...

[Dadio]

The chassis and shock towers do look like devil's to measure , rather you than me

[silvertriple]

Yeah... It seems that the guy who designed it purposely made it complex thinking one would be trying to retro engineer it more than 35 years later and he was probably laughing doing it .

By the way, @Dadio , did you tried print and run any of the Hirobo diff or pulleys? I'm curious as one asked the question about what material to use to print a pulley... I have my doubts on the resistance of the tooth...

[Dadio]

Yeah... It seems that the guy who designed it purposely made it complex thinking one would be trying to retro engineer it more than 35 years later and he was probably laughing doing it .

By the way, @Dadio , did you tried print and run any of the Hirobo diff or pulleys? I'm curious as one asked the question about what material to use to print a pulley... I have my doubts on the resistance of the tooth...

Not exactly , I've printed PB Mini Mustang diffs in bambu labs PA6cf , same belt pitch , worked well but i did deepen the gap between teeth in the model by 0.1mm for FDM , if i left it to spec then when FDM printed the gap became shallow and the belt didn't fully engage .

[silvertriple]

I take note. Thanks @Dadio !

This afternoon, I did work out the universal shafts... All jointed, with the possibility of movements as defined in Fusion 360. That's much better than when you play with dogbones and try to figure out how to joint them so they actually work with the suspensions...


Those things have a huge amplitude...



I also added the wheel driver


That was fairly easy... There will be 4 of those on the chassis...

Spoiler, I decide to let the difficult parts at the end. Rationale : it allows to have the impression to move on, and I needed some success and to finish some parts, because that's too long without finishing parts... Will focus on the central differential next.

[silvertriple]

In order to change a bit, I tackled the front shocks today... Spoiler : they are quite complex.

I've put it to parts first.


One thing that caught my attention is the shock piston, which is unusual, at least for me... It's made of multiple parts, and it is quite smart... And I'll try to show why


I modeled the piston and it's parts...


And then I modeled the shock body. There is a slider in it for one of the piston part...


The principle is simple. The disc has a split on one side, and the second part is sliding in the shock body. If you turn the shock body, the small part turns compared to the disc and opens or close the disc opening. I tried to represent this in few pics...




On the top cap, here whitout the hook (which is turning inside the cap), you find numbers. 0 corresponds to the closed opening, while 9 is going to be the highest flow rate.


Both hooks are fixed (top on the car and bottom on the suspension arm) and the shock body can turn around the shock piston, allowing for a smart setting of the suspension dampening effect...



I found it quite interesting

[silvertriple]

I tackled all the remaining transmission parts... Nothing difficult with straight pinion. This is not like bevel gears, it is easy...

The central diff includes a central gear, to satellite, and internal gear running around all of this.



The shaft act to transmit for the front side, while the rear part is transmitted around the shaft. This is a rather interesting setup...


I will have to finish the chassis modeling to be able to show this in place...