[WIP] Ute supercar

[Zerobricks]

I decided to start a new supercar project and after lots of thinkign decided to make an ute just because nobody else made one yet AFAIK.

For those who don't know what an ute is, it's when a pickup and a normal or sports car really like each other and end up having a child like this:

For this project I set myself the following goals:

1. Unibody construction - The model will have no chassis per-se, the body will be load carrying, something @nicjasno is really good at.
2. Convertible - If you have a sports pickup, why not make it a convertible? This will also force me to make the unibody extremely solid, since there wont be any roof support.
3. Motorized with gearbox - I am using a new high efficiency gearbox idea. Power will be delivered by 4 PF trains motors
4. Realistic suspension - High-gearing solid axle in the back and McPherson suspnsnion in the front

Here's the current progress:

The gearbox has a total of 4 gears. Wave pieces are used to switch between them.

Here's a more detailed view of the setup. As you can see, I used a tilted axle for the overdrive gear:

Since the wave selector pieces can't cope with high torque, the gearbox is designed to work with high speed and low torque. That is why it will be powered by the fastest currently available motors - 4 PF train motors spinning at over 2000 RPM generating around 10Ncm of torque.

The rear axle is an inverted portal design. It' made to be low as possible so that the bed can be placed nice and low.

The axle has a total of 1:12 gear ratio in order to get useful torque from the fast spinning gearbox. Double 24 tooth gears are used in final drive because I expect the car to be quite heavy.

 

So that's the basic idea for now. I will update the topic as I build.

Edited October 12, 2019 by Zerobricks

[romashkaman]

Looks very interesting! But that tilted axle in gearbox... will it be reliable enough? I understand the torque is low, but... I hate u-joints :) Without reinforcing they break very often. Btw, currently I'm in building process of 1:8-1:9 scale car with 8 xl-motors coupled all together... And I can't decide - to use a gearbox or not to use at all. Cars with gearboxes look more complex, but... Is the usage of a gearbox always efficient? Tests will show.

[Fuzzock]

Interesting!! Look forward to the progress.

Ian...

[Zerobricks]

Some more progress.

The rear axle was redesigned, so that the drive axle is placed higher, so that there is minimum angle difference from the gearbox:

The bed is slowly taking shape, and there is enough space in the back for a spare wheel:

[Bartybum]

As an Aussie I’m really looking forward to this :D

[JayDee96]

I'm currently driving a 2017 Redline four door sedan in Light My Fire paint just as your inspiration photo. Your progress looks great. 

[sirslayer]

@Zerobricks I've done a mod of your transmission and I don't own any of the Rotary catches, but I was just curious if the element rotary catches would slide the non friction red color 8 tooth gear on the output axle to engage and disengage to the 24 tooth gear?? ?? here is an example i've built but just a wip!!

 

 

 

 

Technic Changeover Rotary Catch Item No: 35188

Orange▼   Color Images Large Images

[nicjasno]

A few things:

If you are doing a gear reduction in the diff, use the new planetary hubs. The rear axle is way too big and heavy.

When doing a live axle like that, i'd consider using a torque tube.

When making a unibody, have the drivetrain (gearbox+engine) removable and not part of the structure of the car, like in TLG models.

You want to save weight werever possible.

Edited October 13, 2019 by nicjasno

[Zerobricks]

3 hours ago, sirslayer said:

@Zerobricks I've done a mod of your transmission and I don't own any of the Rotary catches, but I was just curious if the element rotary catches would slide the non friction red color 8 tooth gear on the output axle to engage and disengage to the 24 tooth gear?? ?? here is an example i've built but just a wip!!

It should work, but you need a spring to put the gear back when not used.

53 minutes ago, nicjasno said:

A few things:

If you are doing a gear reduction in the diff, use the new planetary hubs. The rear axle is way too big and heavy.

When doing a live axle like that, i'd consider using a torque tube.

When making a unibody, have the drivetrain (gearbox+engine) removable and not part of the structure of the car, like in TLG models.

You want to save weight werever possible.

1. I'm intentionally not using the planetary hubs, because they are inefficient and don't have the high enough gear ratio for what I need.

2. I could use a torque tube, but I'm trying to avoid use of rare elements like this.

3. Since the car will not have the roof, the gear tunnel will have to support a lot of weight. The gearbox can still be made removeable as long as the tunnel is part of the unibody.

Edited October 13, 2019 by Zerobricks

[nicjasno]

I didn't mean the lego torque tube.

More something like this:

[Zerobricks]

That's a nice idea, but a torque tube means the axle would swing and that would mess up my double shock absorber setup.

I thought about using this MacPherson front setup, but the shock absorber is too bendy IRL:

I would need a firmer design, or switch to a normal double wishbone setup.

[Meatman]

Cool. Looks like a modern style El Camino.

[nicjasno]

Use a different shock absorber setup then. Why are you engineering yourself into a corner?

I'd use an elevated double wishbone setup in front.

Edited October 13, 2019 by nicjasno

[Zerobricks]

22 minutes ago, nicjasno said:

Use a different shock absorber setup then. Why are you engineering yourself into a corner?

I'd use an elevated double wishbone setup in front.

I already found a solution by using two soft shock absorbers instead of a single hard one, which doubles my stiffness and helps balance out the force more evenly. Same concept as the double shock abosrbers in the rear, they keep the axle straight and minimize it's bending when accelerating.

[nicjasno]

With the shock absorbers i was thinking about the rear axle.

 

[suffocation]

I'm just gonna follow this thread in awe Same when you start your next project, Nicjasno. You guys always break new ground

[Zerobricks]

Here's the updated front suspension assembly:

As you can see, the whole suspension is at a slight caster angle (5 degrees at the moment). Dual shock absorbers are used to increase stiffness of the arm. The whole upper attachment point can swing in all directions just like a ball joint.

[Nazgarot]

Very interesting solution. How much weight are you expecting this to handle?

-ED-

 

[Zerobricks]

33 minutes ago, Nazgarot said:

Very interesting solution. How much weight are you expecting this to handle?

-ED-

 

I expect the model to weigh around 2-2,5 kilograms. Each small soft shock absorber can handle up to 500 grams, so 8 of them should do the job.

[romashkaman]

23 minutes ago, Zerobricks said:

Each small soft shock absorber can handle up to 500 grams, so 8 of them should do the job.

You always have to remember - that shock absorber can handle 500 grams only if the compression force direction perfectly aligns with the central axle of that shock absorber. That's the basic mechanics, I'm sure you know that. Let's just take a look at 42110 suspension. Model isn't very heavy, TLG used 2 hardest shock absorbers for each wheel, but suspension is soft. And that all is because of the use of the class 3 lever-based suspension.

Sorry if I explain basics :) but in case of your suspension struts there are some different calculations.

Edited October 14, 2019 by romashkaman

[Zerobricks]

2 hours ago, romashkaman said:

You always have to remember - that shock absorber can handle 500 grams only if the compression force direction perfectly aligns with the central axle of that shock absorber. That's the basic mechanics, I'm sure you know that. Let's just take a look at 42110 suspension. Model isn't very heavy, TLG used 2 hardest shock absorbers for each wheel, but suspension is soft. And that all is because of the use of the class 3 lever-based suspension.

Sorry if I explain basics :) but in case of your suspension struts there are some different calculations.

Mine will carry the whole weight directly without any levers.

I made the first physical gearbox test model:

It works very smooth. The idea is to have each of the car's modules (gearbox, engine, axles, etc..) built seperately and to have them removeable.

[Gray Gear]

3 hours ago, Zerobricks said:

I expect the model to weigh around 2-2,5 kilograms. Each small soft shock absorber can handle up to 500 grams, so 8 of them should do the job.

I would be suprised if you can keep the weight below 2.5 kg. My NSX weighs in at like 2.9 kg, and there are no electronics involved 

Still, 2 Hard springs per wheel should be able to support 3kg as well. Good thing you are using a solid rear axle, this way the shocks dont have to face the leverage disadvantage which exists in a independent suspension setup.

[Zerobricks]

Just now, Gray Gear said:

I would be suprised if you can keep the weight below 2.5 kg. My NSX weighs in at like 2.9 kg, and there are no electronics involved 

Still, 2 Hard springs per wheel should be able to support 3kg as well. Good thing you are using a solid rear axle, this way the shocks dont have to face the leverage disadvantage which exists in a independent suspension setup.

I plan to optimize the crap out of the unibody, which will be more or less entirely panel and frame based. If weight exceeds what soft shock absorbers can support, I can easily swap them for hard ones. Actually I'm thinking of using hard ones in the back, so I can carry stuff in the bed.

[Gray Gear]

56 minutes ago, Zerobricks said:

I plan to optimize the crap out of the unibody, which will be more or less entirely panel and frame based. If weight exceeds what soft shock absorbers can support, I can easily swap them for hard ones. Actually I'm thinking of using hard ones in the back, so I can carry stuff in the bed.

Soft Springs? For real? I dont doubt you are able to create a very light unibody, especially if the car is not modelled after a real car, so you have more freedom in panel placement. But do think hard springs will be nececary.

[Zerobricks]

I will be resuming this project with a few changes:

• The model's drive and steering will not be motorized, but it will have motorized raisable suspension like 8297, winch and if possible foldable roof (cabrio).
• All wheel drive with 3 differentials
• Gearbox will be an 8+R speed with an additional 2 speed high and low selector giving a total of 16 gears + reverse.