[WIP] RWD sedan

[tomek9210]

Hello guys,

I started working on a new project. It will be 1:10 sedan with power functions (two L motors and one M motor). As I don't have an access to bricks at the moment, I'm designing it in LDD.

My goals:

- rear multilink axle by Sheepo

- gearbox - not necessary, but it'd be nice to have it

- front axle - semi double wishbone with proper angles

- clutches, so the motors can be disengaged and car can be played manually too

- fake engine - due to design of front axle it's only I4

- chassis at the moment is also by Sheepo, but the front part of it will definitely be changed

Here is my question to you - does it look good? Will it work in real life? Focus on the front axle, rest can be rebuild later (I know I have to strengthen the gearbox). Are the angles ok? I have a problem with attaching top wishbone links properly. As you can see, I attached front ones without a problem, but the back ones give me a headache due to caster angle.

Could someone help me and point me the way how to do it?

Thank you in advance!

[tibivi]

i think it looks pretty good from what i can see, but i think that you're going to have some bump steer.

I also think the engine will be to high, but you can solve that easily with a smaller crankshaft.

also awesome that you care about axle geometry,

[tomek9210]

Thanks for your reply. How can I reduce bump steer?

I'm trying to lower the engine by 1 stud. What smaller crankshaft are you talking about? The one from regular Lego engines?

What do you think about kingpin inclination?

I'm also concerned about only one shock absorber per half axle at the front, but I hope it will hold the weight in reality.

[Didumos69]

Here is my question to you - does it look good? Will it work in real life? Focus on the front axle, rest can be rebuild later (I know I have to strengthen the gearbox). Are the angles ok? I have a problem with attaching top wishbone links properly. As you can see, I attached front ones without a problem, but the back ones give me a headache due to caster angle.

Could someone help me and point me the way how to do it?

It is always hard to build front axles with proper angles. My experience is also that you have to build it for real to see how it performs.

One thing I immediately noticed from what I can see: the shock absorber can easily push the lower wishbone out of the ball joint. And with caster angle it will prove hard to apply liftarms between the upper and lower liftarms. What you could do is try to place the lower wishbone upside-down, that is with its cusps facing downwards.

Edited April 24, 2016 by Didumos69

[zux]

I'm trying to lower the engine by 1 stud. What smaller crankshaft are you talking about? The one from regular Lego engines?

You could use something like this:

[tibivi]

For the crankshaft i have used this idea from lipko (and maybe others) he used it in his 'kisauto' with a v6:

http://www.brickshel...y.cgi?i=5889199

About kingpin inclination: i think it really makes a difference when you 'play' with the model or if it's remote controlled.

For the bump steer, i think that you could reduce it by changing your steering linkage, but that would probably make the steering worse.

The shock absorber should be adequate for the scale.

Edited April 24, 2016 by tibivi

[tomek9210]

I have already reduced height of the engine by 1 stud. It looks much better now. I will post pics later.

As for lower arm and ball joint. I have built it once and it never came apart.

I'm still thinking about placing top links correctly though.

[tomek9210]

I added 5th cylinder too and placed top links in their places. Also I have added servo motor with manually sliding gear to disengage it. I still cannot connect steering linkage with wheel hubs. I think it can be done easily in reality, but due to all the angles it's difficult in LDD.

I'm going to start building it next week. Keep fingers crossed!

[Didumos69]

I have been studying these front axles a little bit better, especially the angles. At first glance caster angle seemed okay, but the 2L offset between the lower ball joint and the upper ball joints would give too much kingpin inclination. However the setup of the upper wishbone (with two links) gives an effective rotation point that lies about 1L (rough estimate) more to the outside of the setup. This reduces the overall kingpin inclination offset to about 1L, which is perfect given the whole setup.

Altogether these front axles result in an effective steering axis that lies almost completely - if not completely - inside the rim, which is actually a quite impressive accomplishment. Together with the kingpin inclination and caster angle it makes this a very realistic setup. Theoratically spoken of course, as I can't draw any conclusions on the stability of the whole thing.

Edited April 25, 2016 by Didumos69

[tomek9210]

Thank you very much! I was trying to get the pivot point inside the rim and Nicjasno's video about multilink suspension helped me a lot. Scrub radius should be minimal too.

I have connected front axle module with chassis and rear axle. I decided to give up 4 speed gearbox and build 2 speed one with M motor and linear actuator for gear changing. If not today, I'll try to start the build tomorrow. Of course I'll post photos and LDD files if I change anything while assembling it.

The car will be red, as I have many Technic pieces in this colour. I haven't decided yet if I will replicate real car. It'd be great to build Alfa Romeo Giulia or Jaguar XF or even BMW 5.

Tomek

[AkiyamaWataru]

I like your design.

i would like to analyse it and learn from it. Would you be so nice and upload the lxf file?

Thanks a lot.

[tomek9210]

Sure, here you are: http://goo.gl/VQoPFA . I will place the gearbox now.

Any suggestions are most welcome!

[Didumos69]

Sure, here you are: http://goo.gl/VQoPFA . I will place the gearbox now.

Any suggestions are most welcome!

Now that you've caught my attention with the front suspension setup, I also took a look at the LXF-file to examine it even better. While doing so I noticed that the bottom side of the front module lacks width-wise stability. Right now the lower wishbones entirely rely on connectors that are being stressed in the same direction as they connect. Once the setup is going to carry weight, the lower wishbone will want to move away from the chassis. Connections are much stronger when forces are applied orthogional to the connection itself.

One way to improve on this is to incorporate one or more width-wise liftarms that help tying together the left and right lower wishbones. See bright yellowish green liftarms in image and LXF-file (sorry for messing with your design).

Edited April 25, 2016 by Didumos69

[tomek9210]

Thank you for your help, that is very kind! I redid the design with your solution. It will add much more strength and stability for sure. I added 2 speed gearbox, it was designed by Sariel for his F1.

Later I will try to figure out how to add motor for gear changing.

Redesigned model: http://goo.gl/kpjYUX

[tomek9210]

This is how it looks now:

http://goo.gl/QAs9a9

I haven't decided which wheel rims I'll use. I like all of them. I added battery box to see how it looks. I placed it above the rear axle to make sure that it will hold the weight. I redid the gear placement at the L motors output to fit the gearbox. I added accelerator pedal engaging L motors. I still have to place gear changing feature.

More to come!

[Didumos69]

Good to know that you added the width-wise liftarms. I didn't look into the details this time, but this is really starting to look like something very cool!

Edited April 26, 2016 by Didumos69

[tomek9210]

Yesterday I started building with bricks. I needed to make some minor changes in steering system, because I didn't like how it worked with servo and I placed different setup with M motor.

Front axle works like a charm. I placed two shock absorbers, yellow and gray one, and it is perfect, everything is solid. Chassis is sturdy. Gearbox works nicely.

Next week I'm going to add interior and start bodywork. Then I'll post some pictures.

[tomek9210]

Hello, time for an update. I decided to give it a go and build Alfa Romeo Giulia. The model drives and steers pretty nicely. Gearbox works fine, there is no gear grinding. Steering is great with M motor and in manual mode when 8 tooth gear is slided off the worm gear. Front suspension is awesome, feel free to copy it and use it in your own models.

Interior is fairly detailed. Front part of the car is going nicely. Check the photos :)

[Didumos69]

Nice progress, it's really starting to look like something! Good to read that the front suspension turns out fine. It's one of the best angled steering setups I've seen in supercars :thumbup: .

[syclone]

Those wheelcovers look great!

[tomek9210]

One more update - front lights, first iteration of it, but I quite like them to be honest. I have changed front bumper a bit too. It looks better now.

I think it looks very predatory :)

[MRP_]

Yeah they look nice! Kind of remind me of an R8, I like it! Lookin good so far!

If you have any red versions of those green pieces in the front though, you might want to switch them out, they kind of stick out.

[tomek9210]

Yes, I will change them, as well as 2L LBG liftarms connected to small panels in the front.

I still need to figure out where to put the IR receiver.

[tomek9210]

Almost a year after last post, I present the update :)

The build was taken apart and started from scratch. My goals were to have more reliable rear suspension, stronger front suspension, v6 engine instead of R4 and realistic look (both interior and exterior) with usage of almost only technic pieces.

As previous it is propelled by 2 L motors, steering by M motor - all motors have clutches, so it is RC/manual car. This was my main goal of this project. The modes are controlled by z12 bevel gears in the main console. It works very nice. HoG steering is from the dashboard.

Front suspension is strengthened, it is still triple arm one - one bottom wishbone and two upper links, two shocks, ackermann steering, kingpin inclination, caster and camber.

Rear suspension is Sheepo's double wishbone one - but for me it is a triple arm suspension - with two bottom arms and one upper arm. It also has two shocks.

V6 engine is covered, I still have to add something to hold the cover while open.

The interior is fairly detailed. Front seats backrests are adjustable, all 3 rear seats are adjustable too, the middle one have hidden armrest. The boot is pretty big. The battery box will be placed in it. The receiver is placed underneath the boot, in the place where spare tire would be placed. I have to check if it works tough :)

Things left to do:

- I want to have the boot cover to be opened by turning a gear.

- I will try to modify the rear part to have hiding tow ball there.

- Finishing the bodywork  :) I loosely base on Jaguar XF.

Rest of pics can be found here:

http://bricksafe.com/pages/tomek9210/lego-technic-red-sedan-wip

 

Your comments are welcome!

 

[Didumos69]

From what I see this remains to be a very promising build . And I love the front axles . A few shots that show the entire car would be nice. Are you planning on updating the LXF-file too?