Didumos69

[MOD] 42056 - Ultimately playable Porsche 911 GT3 RS

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Early this morning I managed to build Box 2 (in 2h30m) and the marriage with Box 1 was no problem. All my MODs fit very nicely. I love it when a plan comes together :classic:.

Edited by Didumos69

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Thanks for the diagram, but that was not the confusion :wink:

My question is in this picture: why does the configuration on the left has the result on the right? Or, in other words, why is the lines intersecting in the center of the rear axle (left image) required to have Ackermann steering (right image)?

7-steering-mechanisms-5-638.jpg?cb=1455682396

I understand the trapezoid is an approximation of the perfect geometry that works for all angles, and probably I could figure out why if I wasn't too lazy to do the geometry :blush:

In any case, I don't want to further distract your topic!

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News on the minimally playable version: A few days ago I asked Blakbird to testdrive (= review) my compilation of the most essential 'community-driven' modifications - a.k.a. minimally playable version of the Porsche. Let me quote: "After everything, the model moves REALLY smoothly." Blakbird provided me with some useful feedback that helped me narrowing down the most essential modifications even further. There were a few things that did not really prove to add to the overall smoothness, for instance the 5x7 frame on top of the gearbox. As a result I decided:

- To replace the 5x7 frame on top of the gearbox with a more simple support for the axle running from the D+N+R gearbox to the differential.

- To drop the improved support for the toggle joint in the D+N+R gearbox. It didn't really add much and required a 13L liftarm to be replaced with an 11L liftarm.

- To revert to Attika's suggestion to simply flip the changeover catches in the PDK-unit instead of replacing them with 2L (+0)-liftarms. The replacement didn't really make much difference.

This means that the overall recipe for succes now boils down to the following modifications (I also updated this list in the OP of this thread). In case I will be able to narrow down this compilation of modifications even further, I will of course report on that in this thread. But that does not withstand the fact that the current set will guarantee a smoothly moving Porsche. Btw, especially for the gear shifting MODs it is important that you apply all of them. They rely on each other:

Gear shifting MODs (link)

- Apply Paul Boratko's gear sequence fix as described in Jim's review.

- Flip the change-over-catches in paddle-shifter-unit by 180 degrees (as suggested by Attika).

- Add the simple 90° limiter to the gear selecter axle; use two of the four white silicon bands.

- Remove the 8 tooth gears used to add friction; minimize friction in the selecter axle instead.

- Use only one silicon band for each paddle shifter; wrap it around the neck of the ball joint once.

- Extend both change-over-catches in the gearbox with half a stud (more info here).

Friction reducing MODs (link)

- Remove the pinjoiner in the D+N+R-gearbox. Original idea suggested by Blakbird, see his detailed build report.

- Avoid red gears from transferring torque on axles rotating at different speed, see eliminate friction in gearbox.

- Add an extra support for the 15L axle running from D+N+R gearbox to differential, see alternative axle scheme.

- Avoid axle connectors from rubbing against liftarms as suggested by nerdsforprez, see alternative axle scheme.

- Replace the white clutch gear with a gearless friction clutch, see alternative axle scheme and white gear replacement.

- Now you can gear up the engine: Replace the 2 16t gears with a pair of 24t-8t gears, see eliminate friction in gearbox.

I also made an updated LXF-file available that reflects these modifications in terms of groups. In each group there is a subgroup representing the old structure and the new structure. In the LXF-file all new structures are embedded in the chassis and all old structures are placed to the side of the chassis. By clicking on a subgroup you select all parts in that group. That way you can inspect the differences. Besides the 'Minimal version' modifications listed above it contains HoG steering and a 4th to 1st gear block. If you want, you can skip the HoG steering; it's not essential for a smoothly moving model.

Next step will be to provide instructions by means of an errata-sheet with references to the building steps in the original building instructions and a parts list.

Enjoy!

Edited by Didumos69

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News on the minimally playable version: A few days ago I asked Blakbird to testdrive (= review) my compilation of the most essential 'community-driven' modifications - a.k.a. minimally playable version of the Porsche. Let me quote: "After everything, the model moves REALLY smoothly." Blakbird provided me with some useful feedback that helped me narrowing down the most essential modifications even further. There were a few things that did not really prove to add to the overall smoothness, for instance the 5x7 frame on top of the gearbox. As a result I decided:

- To replace the 5x7 frame on top of the gearbox with a more simple support for the axle running from the D+N+R gearbox to the differential.

- To drop the improved support for the toggle joint in the D+N+R gearbox. It didn't really add much and required a 13L liftarm to be replaced with an 11L liftarm.

- To revert to Attika's suggestion to simply flip the changeover catches in the PDK-unit instead of replacing them with 2L (+0)-liftarms. The replacement didn't really make much difference.

This means that the overall recipe for succes now boils down to the following modifications (I also updated this list in the OP of this thread). In case I will be able to narrow down this compilation of modifications even further, I will of course report on that in this thread. But that does not withstand the fact that the current set will guarantee a smoothly moving Porsche. Btw, especially for the gear shifting MODs it is important that you apply all of them. They rely on each other:

Gear shifting MODs (link)

- Apply Paul Boratko's gear sequence fix as described in Jim's review.

- Flip the change-over-catches in paddle-shifter-unit by 180 degrees (as suggested by Attika).

- Add the simple 90° limiter to the gear selecter axle; use two of the four white silicon bands.

- Remove the 8 tooth gears used to add friction; minimize friction in the selecter axle instead.

- Use only one silicon band for each paddle shifter; wrap it around the neck of the ball joint once.

- Extend both change-over-catches in the gearbox with half a stud (more info here).

Friction reducing MODs (link)

- Replace the pinjoiner in the D+N+R-console by bushes as suggested by Blakbird, see his detailed build report.

- Avoid red gears from transferring torque on axles rotating at different speed, see eliminate friction in gearbox.

- Add an extra support for the 15L axle running from D+N+R gearbox to differential, see alternative axle scheme.

- Avoid axle connectors from rubbing against liftarms as suggested by nerdsforprez, see alternative axle scheme.

- Replace the white clutch gear with a gearless friction clutch, see alternative axle scheme and white gear replacement.

- Now you can gear up the engine: Replace the 2 16t gears with a pair of 24t-8t gears, see eliminate friction in gearbox.

I also made an updated LXF-file available that reflects these modifications in terms of groups. In each group there is a subgroup representing the old structure and the new structure. In the LXF-file all new structures are embedded in the chassis and all old structures are placed to the side of the chassis. By clicking on a subgroup you select all parts in that group. That way you can inspect the differences. Besides the 'Minimal version' modifications listed above it contains HoG steering and a 4th to 1st gear block. If you want, you can skip the HoG steering; it's not essential for a smoothly moving model.

Next step will be to provide instructions by means of an errata-sheet with references to the building steps in the original building instructions and a parts list.

Enjoy!

P.S. Here's an image showing the complete set of modifications. The original parts are in the background:

Your efforts are very much appreciated! I have had my Porsche sitting and waiting for this to be completed so I can build it. Are you still going to making BI / erratum sheet for all the changes to make it even easier to apply them?

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Your efforts are very much appreciated! I have had my Porsche sitting and waiting for this to be completed so I can build it. Are you still going to making BI / erratum sheet for all the changes to make it even easier to apply them?

I do intend to make instructions in terms of errata for the minimally playable version soon. For the ultimately playable version I will probably only provide a LXF-file showing all differences in terms of groups.

Edited by Didumos69

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On another note, and I may have to ask this in the mods and improvements thread as well, but has anyone thought about making the front wheels higher. The clearance is really, really terrible when the body is attached. So much so that you can barely compress the front shocks at all. I may try it myself, but then again, time is my most limiting factor, as well as skill at this point.

Maybe we should simply change the front shocks with yellow ones with a higher stiffness ?

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I did see that fix, yes. I have not tried it yet, as I did not like how the rims would rub against the wishbone pieces. But I did not see your edit. I might try it tonight then.

Although I want to come up with a more sophisticated solution. But that may take me some time.

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Although I want to come up with a more sophisticated solution. But that may take me some time.

I would love to see a more sophisticated solution. :thumbup:

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This is what I came up with for improving the clearance in the front. It works without the body and without a stopper as well, although the rims will touch the upper wishbone pieces when steering, but not to a point where it stresses the rims or wishbone pieces and could cause harm.

800x1067.jpg

800x600.jpg

With this mod applied, and the body back on the chassis, the front shocks have about as much travel as the rear ones.

Edit: I quickly discovered that the half pins limit the travel of the gear rack somewhat. Perhaps there is another way to secure the L-shape thin liftarms to the wishbone pieces?

Edited by ddeklerk

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I didn't see you posted this here too. I'm going to try to integrate it in my ultimately playable build. Thanks for posting!

Edited by Didumos69

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This is what I came up with for improving the clearance in the front. It works without the body and without a stopper as well, although the rims will touch the upper wishbone pieces when steering, but not to a point where it stresses the rims or wishbone pieces and could cause harm.

With this mod applied, and the body back on the chassis, the front shocks have about as much travel as the rear ones.

Edit: I quickly discovered that the half pins limit the travel of the gear rack somewhat. Perhaps there is another way to secure the L-shape thin liftarms to the wishbone pieces?

Unfortunately the 3x3 levers collide with the steering rods in my build. Because of the Ackermann steering the steering rods move more towards the 3x3 levers than in the stock model. I think it's still a good concept for the stock model though.

So I've been playing around with LDD and came up with something that I plan to implement in my playable build soon. By making use of the full length of the suspension arms I could increase the ground clearance by half a stud without introducing more angle in the suspension arms, Too much angle will cause the upper suspension arm to hit the inside of the rim in turns. Another advantage of using the full length of the suspension arms is that bump steer is eliminated, because the steering rods and suspension arms now have the same length. This setup also improves the way the suspension arms are secured; they are far less wobbly than in the stock model (I did some prototyping). And finally, I could add two extra shocks to make the suspension more resistant. The setup still includes Ackermann steering and a gear rack slider. The suspension travel is one stud.

800x450.jpg800x450.jpg800x450.jpg

Edited by Didumos69

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Looks quite complex what you came up with there. Unfortunate that my suspension mod does not work with the steering mod. Although I doubt that I am finished with it either way.

There still were some flaws that I only realized today I should probably fix. In my mod the shocks are always compressed at least a little bit. This means that there is more pressure on the springs themselves, which could lead to damage in the long term. Or in the very least it would wear the springs out more quickly.

I also want to wrap my head around Ackermann steering as a concept, since I don't fully understand it yet. And then I may make my own implementation of it.

After that I would like to try making rear wheel steering. That is something that I see people mention a lot when mentioning what features are missing from the Porsche. But perhaps I am getting a bit ambitious with all of this. I also still have my model of Lockdown that I want to finish sometime. But that's a different story altogether.

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Looks quite complex what you came up with there. Unfortunate that my suspension mod does not work with the steering mod. Although I doubt that I am finished with it either way.

There still were some flaws that I only realized today I should probably fix. In my mod the shocks are always compressed at least a little bit. This means that there is more pressure on the springs themselves, which could lead to damage in the long term. Or in the very least it would wear the springs out more quickly.

I also want to wrap my head around Ackermann steering as a concept, since I don't fully understand it yet. And then I may make my own implementation of it.

After that I would like to try making rear wheel steering. That is something that I see people mention a lot when mentioning what features are missing from the Porsche. But perhaps I am getting a bit ambitious with all of this. I also still have my model of Lockdown that I want to finish sometime. But that's a different story altogether.

I think it looks more complex than it actually is... I hope :classic:. Maybe I can simplify some things while building. In this setup the additional yellow shock is also slightly compressed when the red one is completely expanded. I don't think it's that bad, because the weight of the body will stress the shocks even more.

I'm curious what your version of Ackermann geometry will look like. And rear wheel steering sounds indeed ambitious! :thumbup:

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Unfortunately the 3x3 levers collide with the steering rods in my build. Because of the Ackermann steering the steering rods move more towards the 3x3 levers than in the stock model. I think it's still a good concept for the stock model though.

So I've been playing around with LDD and came up with something that I plan to implement in my playable build soon. By making use of the full length of the suspension arms I could increase the ground clearance by half a stud without introducing more angle in the suspension arms, Too much angle will cause the upper suspension arm to hit the inside of the rim in turns. Another advantage of using the full length of the suspension arms is that bump steer is eliminated, because the steering rods and suspension arms now have the same length. This setup also improves the way the suspension arms are secured; they are far less wobbly than in the stock model (I did some prototyping). And finally, I could add two extra shocks to make the suspension more resistant. The setup still includes Ackermann steering and a gear rack slider. The suspension travel is one stud.

800x450.jpg800x450.jpg800x450.jpg

Nice idea, with two shocks. I tried also to use the full length of the wishbones, but failed : my car was touching the ground, since the effect of the shock absorbers is reduced. Consequently, your mod is very interesting ^^. Have you tried with the body ?

Edited by DayWalker

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Nice idea, with two shocks. I tried also to use the full length of the wishbones, but failed : my car was touching the ground, since the effect of the shock absorbers is reduced. Consequently, your mod is very interesting ^^. Have you tried with the body ?

I still have to build it, the images are renders. To be honest, I still have to finish Box 3 and 4 :blush:

Edited by Didumos69

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Wow, I completely missed this topic all the time. I think I confused it with the other general Porsche MOD topic (which I stopped reading a while ago since I don't have the Porsche yet). Anyway...

I'm still in doubt about the Porsche. It's a ton of money for a Lego Technic set (that feels like 80% bodywork instead of features to me). I'll probably wait for a good sale.

But, all your mods and improvements sure look great Didumos and it makes the Porsche look way more interesting than the standard set. I'll keep this topic in mind when I eventually get the set. Nice work! :classic:

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But, all your mods and improvements sure look great Didumos and it makes the Porsche look way more interesting than the standard set. I'll keep this topic in mind when I eventually get the set. Nice work! :classic:

Thanks!

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BAD NEW ? You should really try with the body (and so finish it...). On my car, with your geometry, the 2 red shocks are not strong enough...

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BAD NEW ? You should really try with the body (and so finish it...). On my car, with your geometry, the 2 red shocks are not strong enough...

Perhaps it's time to build box 3 and 4 :wink:

Are you sure you have the same geometry? You need 4 of the hardest shocks. I'm quite certain the resistance is stronger than the original geometry. I tested with a prototype before actually building this. The weight of Box 3 and 4 together is approximately 1kg, so I tried with 1050gr soya milk leaning on the dashboard and the roll bar behind the seats. The center of gravity in the middle of the car and this is the result:

Edited by Didumos69

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Not sure at 100% since I had to take one of the back red shocks and my bulding was not symmetric. But apparently, it was not enough. In fact, when doubling the length of the wishbones, we need to double the strength of the shocks for the same geometry. If we change the geometry, this may change... and I think that using the diagonal of the parallegram is one of the most efficient solution (or an almost vertical shock as close as possible to the wheel).

Edited by DayWalker

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In fact, when doubling the length of the wishbones, we need to double the strength of the shocks for the same geometry. If we change the geometry, this may change... and I think that using the diagonal of the parallegram is one of the most efficient solution (or an almost vertical shock as close as possible to the wheel).

In my setup the wishbones did not exactly double in length, they went from 3 to 5 studs (heart to heart). The outer shock also stands more vertically than in the stock geometry. So the outer shock has more than half the strength of the original setup. When I tested this setup, the outer shock almost gave as much resistance as the stock geometry. The second shock adds just enough to get the right strength. It shouldn't be too strong either. Btw, here's the LXF-file of my front suspension.

800x450.jpg800x450.jpg

But now that I've finished box 3 and 4, and could conclude the front suspension works okay (see image), there was something I was less content with. The rear suspension. The front ground clearance was actually better than the rear ground clearance. Maybe because of the 361 extra parts - and counting - that I added, So I decided to finetune the rear suspension as well. I moved the point where the shocks are mounted to the lower suspension arms 1 stud more to the outside of the suspension. I also had to mount the calipers differently to make some room for this adjustment (this fits the rims perfectly). Then I lowered the point where the shocks are mounted to the chassis by half a stud. This gives just the right amount of extra strength and the front and rear ground clearance are now the same. And a nice side effect is that the shocks are now parallel to the ones in the front suspension. This is what I did:

800x450.jpg800x450.jpg

This shows the overall ground clearance very nicely:

1600x450.jpg

Edited by Didumos69

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This gives just the right amount of extra strength and the front and rear ground clearance are now the same

Didumos69, isn't the original Porsche has positive rake angle?

I look at the original pictures (as mine is already heavily modded, mostly with your suggestions) and it has positive rake angle too.

So rear ground clearance HAS to be more than front ground clearance so that the Porsche nose is pointing downwards (as the floor of 42056 is perfectly flat).

Currently I tweak the rear suspension about half stud from the stock version as I put 2 heavy >< battery boxes at the back. My front clearance is 1 stud, back clearance 1.5 stud.

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