[MOC] Rugged supercar - Hammerhead (1:9 scale) - Revisiting

[stevenhalim]

@arshialQ, I have been trying to RC this and currently have this conclusion that 4 gear ratios, no matter how you configure it, are currently too much for the current Lego Technic system.

On the lowest gear 1, most likely the torque is too much and something will likely break (the weakest link) in the drivetrain, usually cv joints, diffs, center diff (I feel the older diff is structurally weaker than the newer one).

On the highest gear 4, most likely the speed is too much and torque is too low and the ~2kg model cannot move at all.

In real life vehicle, people normally start with lowest gear, move the vehicle, and upshift when the vehicle has attained sufficient speeds. But that means you will need another servo to toggle the gear shift mechanism (additional IR receiver and additional controller, or you have to use SBrick).

I have tried all that and currently not satisfied with the playability, so, still thinking.

[arshiaIQ]

On Wednesday, June 14, 2017 at 0:50 AM, Didumos69 said:

3 hours ago, stevenhalim said:

@arshialQ, I have been trying to RC this and currently have this conclusion that 4 gear ratios, no matter how you configure it, are currently too much for the current Lego Technic system.

On the lowest gear 1, most likely the torque is too much and something will likely break (the weakest link) in the drivetrain, usually cv joints, diffs, center diff (I feel the older diff is structurally weaker than the newer one).

On the highest gear 4, most likely the speed is too much and torque is too low and the ~2kg model cannot move at all.

In real life vehicle, people normally start with lowest gear, move the vehicle, and upshift when the vehicle has attained sufficient speeds. But that means you will need another servo to toggle the gear shift mechanism (additional IR receiver and additional controller, or you have to use SBrick).

I have tried all that and currently not satisfied with the playability, so, still thinking.

I currently havent done bodywork yet, and it moves without struggle with a single xl motor, directly connected to the middle 16t geat in the gearbox. On fourth gear, current problem is that driving rings kinda "slip" out of the red gears and clicking sound starts and vehicle no longer moves...

Shifting mechanism is easily RC-able with a servo, reduced to 1:2 ratio... one seat is likely to be sacrificed though. I have done it and it shifts well, if only return-to-center is disabled. I have also done that. So current problem seems to be the slipping of the driving ring on 4th. Maybe we could change one of red connectors inside driving rings to those white ones... the are stronger in holding their position. Problem is that the servo is already struggling to shift

Edited June 15, 2017 by arshiaIQ

[Didumos69]

2 hours ago, arshiaIQ said:

I currently havent done bodywork yet, and it moves without struggle with a single xl motor, directly connected to the middle 16t geat in the gearbox. On fourth gear, current problem is that driving rings kinda "slip" out of the red gears and clicking sound starts and vehicle no longer moves...

Shifting mechanism is easily RC-able with a servo, reduced to 1:2 ratio... one seat is likely to be sacrificed though. I have done it and it shifts well, if only return-to-center is disabled. I have also done that. So current problem seems to be the slipping of the driving ring on 4th. Maybe we could change one of red connectors inside driving rings to those white ones... the are stronger in holding their position. Problem is that the servo is already struggling to shift

Using the white connectors with ridges inside the driving rings doesn't work. The 90 degree limiter is not strong enough to make the rings pass the ridges. Two things that might help:

• Tighten the 90 degree limiter: Add extra silicon bands around the 2L liftarms as depicted below. Downside is that you need more power to shift.
• Shorten the change over catches as depicted below, so the driving rings are forced into the clutch gears a little deeper. Downside is that this may induce more friction as the clutch gears may get squeezed between the driving rings and the liftarms behind them.

Edited June 15, 2017 by Didumos69

[PorkyMonster]

 

23 hours ago, Didumos69 said:

Shorten the change over catches as depicted below, so the driving rings are forced into the clutch gears a little deeper. Downside is that this may induce more friction as the clutch gears may get squeezed between the driving rings and the liftarms behind them.

After seeing the comments by @arshiaIQ and @stevenhalim, I've decided to do a quick test - not directly with HH (there'll be too tough for me... ), but rather building a new quick-n-dirty chassis using the same gearbox and fit it with the larger 94.3mm wheel and drive it with 2 L motors and 2 battery boxes. And I happened to have done exactly what @Didumos69 suggested regarding the change over catches.

With a weight of 1.3 kg, I piled on top the HH - so total weight becomes about 3.2 kg, and the only issue I found was some gear slippage (I can't pin-point exactly where though... could be the differentials at the axles) during acceleration and stopping with 3rd (lesser) and 4th gears (more). I suspect that slippage can be solved by using the clutch gear somewhere early in the drive train... will try that out later on.

So I think the gear box is fine, even with wide gear difference and more than 3 kg.

Edit: Just tested with a 24-tooth clutch gear  inserted between the motors and gearbox, and gear slippages during acceleration disappeared. For lower gears, torque and speed not affected... but for 3rd and 4th gear, acceleration slowed, and it takes longer to reach top speed - this is quite realistic, because in real car, the driver usually starts at lower gear, then advance towards higher gear as the car picks up speed.

Edited June 16, 2017 by PorkyMonster

[BusterHaus]

9 hours ago, Didumos69 said:

Using the white connectors with ridges inside the driving rings doesn't work. The 90 degree limiter is not strong enough to make the rings pass the ridges. Two things that might help:

• Tighten the 90 degree limiter: Add extra silicon bands around the 2L liftarms as depicted below. Downside is that you need more power to shift.
• Shorten the change over catches as depicted below, so the driving rings are forced into the clutch gears a little deeper. Downside is that this may induce more friction as the clutch gears may get squeezed between the driving rings and the liftarms behind them.

I tried the white connectors during my initial build and I think the second solution may work.  These connectors offer too much resistance and don't allow the sliding ring to travel far enough to engage the red gears.  You need to over-travel the catch (maybe by 10 degrees?) and then come back into the 90 degree position with it.  It's much easier with the new smooth connectors.

While I was building a version of the Porsche gearbox with your 90 degree limiter I thought about replacing  attached by the rubber bands with and using the torsion of the axle to lock the position in place.  If I remember correctly a test build worked well enough, but I went with the rubber band method to always have contact with the #2 connector.

[Duky]

I tried to order the 4 wheel rims from the Porsche via lego hotline.

They told me, that you can't order the Rims anymore because this a licensed lego product.

Have anybody noticed that? Because in November 2016 it was possible to the order this special part.

[Didumos69]

3 hours ago, Duky said:

I tried to order the 4 wheel rims from the Porsche via lego hotline.

They told me, that you can't order the Rims anymore because this a licensed lego product.

Have anybody noticed that? Because in November 2016 it was possible to the order this special part.

That's bad news! I hope this doesn't mean the Porsche rims are going to be a rarity.

[GordyMcPatty]

Excellent job!

[Didumos69]

21 hours ago, GordyMcPatty said:

Excellent job!

Thanks!

[Didumos69]

I didn't want to disturb @Erik Leppen's topic with this side-discussion any further, so I moved to this thread.

7 hours ago, Didumos69 said:

Indeed. I tried to reason what @Erik Leppen's 'arm' means for my rugged supercar suspension and came to the conclusion that my setup (left in the image below) behaves as if the spring was positioned as in the right half of the image below. I actually translated the springs along the suspension arms away from the wheel. The red parts indicate the 'arm'-length. EDIT: I corrected the image.

 

3 hours ago, PorkyMonster said:

Hmm... had you actually positioned the spring as in the right half of the image, you would have had stiffer suspension... So I think they (the left and the right setups) don't behave the same way. Of course, the fact that the top of the spring in the right image setup is not static adds some complications.

I tend to see this differently. Translating the shock along the parallel wishbones does not affect the way the compression of the shock relates to the vertical movement of the wheels. It would always compress the same, unless the suspension arms would bend of course, but then I would no longer consider the suspension arms as parallel.

Edited June 24, 2017 by Didumos69

[PorkyMonster]

7 hours ago, Didumos69 said:

Translating the shock along the parallel wishbones does not affect the way the compression of the shock relates to the vertical movement of the wheels. It would always compress the same, unless the suspension arms would bend of course, but then I would no longer consider the suspension arms as parallel.

Right, that's where my point on "some complications" come into play . Naturally, the spring will gain more compression the closer it is to the wheel, given the same wheel travel. However, because of non-static top end, this gain in compression will be negated to some extent. And in your case, the parallel nature of the wishbones cause a negation that equals to the gain, hence you get the same effective compression.

This being the case, your determination of the arm-length based on the image on the right will be meaningless, since there can be infinite different arm-lengths giving the same compression. Instead, the rightful arm-length should be based on the original image on the left, where the top of the spring is static.

[Didumos69]

For those living nearby Boekelo, Overrijssel (The Netherlands): My rugged supercar will be on display during the 'Bouwen met LEGO'-event from 8th to 10th of August. I won't be there myself, but my twin brother will be happy to demonstrate the model .

[Rudivdk]

Same for me, 198km... Would have loved to see it IRL too...

[Didumos69]

3 minutes ago, LvdH said:

That't too far for me  134 km drive. Would've loved to come for sure. Any idea if you'll still have it built when LEGO World starts again?

Too bad. I have no plans to take it apart any time soon, so yes, I will still have it built during LEGO World. Why do you ask? It would be great to have it on display there as well, but I don't know how to arrange that...

1 minute ago, Rudivdk said:

Same for me, 198km... Would have loved to see it IRL too...

That's an amazing distance in such a small country .

[Rudivdk]

3 minutes ago, Didumos69 said:

Too bad. I have no plans to take it apart any time soon, so yes, I will still have it built during LEGO World. Why do you ask? It would be great to have it on display there as well, but I don't know how to arrange that...

That's an amazing distance in such a small country .

I live on the coast so its from border to border... cant get any further I guess 

I would be interested in finding out how to display something on LEGO World as well, if that is even possible. Would be a good deadline to finish my familycar MOC... Do you have to be a member of some sort of club or something?

Before derailing this topic into LEGO World discussion, does it make sense to start a separate topic on that?

Edited July 24, 2017 by Rudivdk

[Didumos69]

Is there anyone hosting a stand at LEGO World 2017 who would be willing to display my rugged supercar (my personal build)? It would be great if it could be displayed there somehow. I will take care of transport and a description-sheet myself. Please PM me if you could help me out. Thanks!

Btw, I made a collection of POVRAY renders. I'm slowly getting the hang of it.

[suffocation]

I just ordered the handful of parts I'm short of to build this masterpiece. I'll try to exhibit it at Lego events here in northern Italy and possibly in Canton Ticino, if that's okay with you.

[Aventador2004]

I wish I could, but I believe it is halfway around the world from me. It would of course be a pleasure to display and talk about. You should make a plaque for it, on a brick showing it is yours.

[Alex Ilea]

Would be cool to see this car in blue.

[Didumos69]

20 hours ago, suffocation said:

I just ordered the handful of parts I'm short of to build this masterpiece. I'll try to exhibit it at Lego events here in northern Italy and possibly in Canton Ticino, if that's okay with you.

Cool! Of course that's okay with me. Please share pictures when it's finished (or while building).

19 hours ago, Aventador2004 said:

You should make a plaque for it, on a brick showing it is yours.

I will.

18 hours ago, LvdH said:

I hope to build it before 2018, I already got ~2200 of the parts. I will be building it in white: 

Nice. You might also consider replacing some parts with LBG parts, for instance in the area where the hood connects to the left and right flanks. In your screenshot the hood seems a little disconnected from the rest of the body.

17 hours ago, IA creations said:

Would be cool to see this car in blue.

Most parts are available for a blue version. Only the bigger panels in the mid-section of the hood and for the rear lights need to be replaced with a different color. Black could be an option:

[Didumos69]

10 minutes ago, LvdH said:

Also some connectors, like the ones on the rear connected to the 5L liftarms. And those on the front are rarer than you think... and of course the bushes.

So it won't be that easy.

10 minutes ago, LvdH said:

What do you mean?

I mean the in the hood close to the dashboard that you painted black. If I recall correctly @PorkyMonster mixed white and LBG parts to get a white version, but a true black and white version would of course be cooler.

[suffocation]

10 hours ago, Didumos69 said:

Cool! Of course that's okay with me. Please share pictures when it's finished (or while building).

Sure will! If you want, you can also send me a presentation in Dutch and English; I can translate it into Italian and have it translated into French and German. Maybe we can add some WIP pictures so visitors get a real feel for the building experience.

Quick question: on step 15, is there a particular reason for using the assembly on the left rather than the one on the right?

Edited August 28, 2017 by suffocation

[Didumos69]

16 hours ago, suffocation said:

Sure will! If you want, you can also send me a presentation in Dutch and English; I can translate it into Italian and have it translated into French and German. Maybe we can add some WIP pictures so visitors get a real feel for the building experience.

Thanks for the offer! I was thinking of a single page plaque (A4). I'll work something out.

16 hours ago, suffocation said:

Quick question: on step 15, is there a particular reason for using the assembly on the left rather than the one on the right?

Yes, there is. In the left version the tow ball sticks out 1/5th of a stud more, which adds to the straight alignment of the shifting link (seen from above). The angle made by the shifting link (seen from above) affects how deep the driving rings insert into the clutch gears. As the angle grows, the rear clutch gears are inserted deeper and the front clutch gears are inserted less deep, which could easily trouble another optimization: The length of the change-over catches on the other end of the shifting links has been optimized to avoid double engaged gears and to avoid clutch gears from getting squeezed against liftarms. They have been lengthened by approximately half a stud. However, longer catches also cause the driving rings to insert less deep into the clutch gears. If the angle made by the shifting link (seen from above) would unbalance the insertion depth over the front and rear clutch gears too much, the front clutch gears might not be inserted deep enough and the rear clutch gears might get squeezed after all. So this is why the straight alignment of the shifting link (seen from above) is important.

Nevertheless, it might still work with the right version. It's a matter of optimization.

In an early version of the chassis I used your right version and lengthened the catches even more than in the final model. You can see the inclination of the links verywell in this picture:

However, it was @Meatman who noticed the front clutch gears were only engaged halfway:

On 2-12-2016 at 6:20 PM, Meatman said:

I also notice that the driving rings are only engaging about halfway when they are shifted forward. It may be because the links you are using are not even?

So:

On 3-12-2016 at 2:37 PM, Didumos69 said:

@Meatman, I managed to improve the shifting links. You were right that the links were disaligned by almost 1 stud over their full length. The intention was to lengthen the change-over catches max .5 stud to avoid friction and double engaged gears, but I extended them by appr. .75 stud. Together with the ball-joint with axle that doesn't fully insert the disalignment was simply too much. So I removed two half bushes to make sure the catch extensions are exactly .5 stud and at the same time I replaced the +0 liftarms attached to the shift axle with 2 2L thin liftarms and the attached ball-joints with pin with ball-joints with axle. This also reduces the disalignment. Now the red clutch gears at the front are engaged practically as good as the ones in the back of the gearbox without reintroducing any squeezing or double engaged gears.

Thanks again for pointing this out. It made the whole setup work even better.

 

Edited August 29, 2017 by Didumos69

[suffocation]

Ah, makes perfect sense! The level of precision in this build truly is impressive.

[Didumos69]

For those interested in motorizing this model: I just spotted this thread on the German Dokter Brick forum. It's about motorizing drive and steering. You can find a LXF-file of the motorized chassis there too.