[WIP] RC Off-roader w/ Dual Diagonal Drive

[schraubedrin]

1 hour ago, Didumos69 said:

I think I will leave it as is

I think i understand it as far as possible without trying to build it myself
You've obviously put a lot of thought in this already.

1 hour ago, Didumos69 said:

.

It's crazy how well this concept fits in your current design language

 

1 hour ago, Didumos69 said:

I'm following my standard layered approach: I work lengthwise on odd layers (counting from bottom to top) and transversal on even layers.

That sounds like a really solid strategy. Now i'm really keen to see you working on LDD

[Didumos69]

1 hour ago, KevinMoo said:

I really can’t figure out how to improve it anymore, could be the result of too much frictions. I’ll probably give it up for future projects.

So my suggestion is to be very careful with central diff, it could be the weakest part of the whole chassis even with two of them.

Thank you for your reply and your advice @KevinMoo. I will be carefull and I will testing stuff before finishing the whole design.

I do see some difference between your approach and mine. You use a clutch gear to transfer drive on an axle that rotates at different speed. That gives a lot of friction, more than you would think, but it is of course not the cause of the differential problem. Another difference is the torque. I geared up the motor-output with 3:1 and 5:3. You geared the motor-output down with 3:5. Gearing down means more torque. I hope to tackle the differential problem with very smooth running gears (all axles supported at both ends, no chance of squeezed gears and no clutch gears on axles running at different speed) and high spin / low torque in the differentials.

Edited November 30, 2018 by Didumos69

[Didumos69]

3 hours ago, schraubedrin said:

I think i understand it as far as possible without trying to build it myself
You've obviously put a lot of thought in this already.

It's not visible in my renders, but the differential meshes with an 8t gear at its 24t side, just like in @KevinMoo's renders. Only in his renders the 8t gear sits on the same axle as the 16t clutch gear at the other end of the differential. In my case this axle is split into two, one for the 16t gear and one for the 8t gear, so no clutch gear. To lock the differential I make the axle with the 16t gear engage with one of the outputs of the differential. I can't do that by making the axle with 8t gear engage with the other outputs, because that axle rotates 3 times faster.

EDIT: Added renders.

Edited November 30, 2018 by Didumos69

[pagicence]

Well I'm rooting for the Zarooq SandRacer or something more scarier. I'm hoping that you will do something similar like Hammerhead design wise, something angular and half open.

6 hours ago, Didumos69 said:

I might also add an M-motor for the v8.

May I suggest that you don't, because you already have that solution in Greyhound (unless it's necessary). Try something different instead. Also have you thought about 4 wheel steering? It might be interesting for this project. (pardon my suggestions I am overly excited about this project , I keep spitballing ideas here).

Edited December 1, 2018 by pagicence

[deehtha]

Taking the drive for both motors for the fake engine should be unnecessary. If you take just one output to the fake engine, you should be able to simplify that area up. The drag on the one side from the fake engine should be negligible. 

[schraubedrin]

5 hours ago, Didumos69 said:

Added renders

Thank you very much for the pictures, this clears things up quite a bit.

I have to admit, i thought you had only put in those 16t-clutch gears as placeholders with the complete gearbox coming later

This small and compact design really surprised me.

[Didumos69]

On 12/1/2018 at 12:57 AM, pagicence said:

May I suggest that you don't, because you already have that solution in Greyhound (unless it's necessary). Try something different instead. Also have you thought about 4 wheel steering? It might be interesting for this project. (pardon my suggestions I am overly excited about this project , I keep spitballing ideas here).

Feel free!

On 12/1/2018 at 1:24 AM, deehtha said:

Taking the drive for both motors for the fake engine should be unnecessary. If you take just one output to the fake engine, you should be able to simplify that area up. The drag on the one side from the fake engine should be negligible. 

I will stick to the diff for the fake engine for now. Sofar I can quite easily make a manual model out of this by just removing the motors. Also the stepper can be made manual quite easily. Speaking of the stepper, I checked the setup I have in mind and it works. The method itself is not new, I simply never tried a setup with the input and output along the same axis.

 

Edited December 3, 2018 by Didumos69

[Didumos69]

Did some work on the front suspension. I used the hubs from my Greyhound, I haven't decided about the wheels yet, so for now I also added the Greyhound wheels. No special angles this time. It does have Ackermann geometry and it is controlled with a Servo-motor. The max angle is about 20 degree, so the control should not be too nervous. The A-arms are 6 studs long (5 studs center-co-center). The gearrack is located underneath the yellow knob wheels used for shifting. It is actually a pleasure to not have a differential between the front wheels. It allows for the steering axle to run right between the left and right toggle joints at the end of the drive train.

Edited December 7, 2018 by Didumos69

[gate]

God, your renders are so beautiful

The clearance isn't too big though.

[Rudivdk]

At this pace you'll be done before xmas... so much for keeping you busy through the winter.

But seriously, it's looking beautiful. Are you already planning on the physical build? I'm really interested to see how it performs 'in the brick'...

[Attika]

You made quite a progress, and it looks very elegant all around. 

Let me highlight your laziness: The tread on the wheels point different direction on each side. (copy-paste?)  

And I 2nd on what Rudivdk said. This project won't last till spring comes if you keep going like this.

By the way is there any plan to turn this into plastic? (I know, it's to much pressure from us but great power comes with great responsibility )

[Didumos69]

Thanks guys!

3 hours ago, Rudivdk said:

Are you already planning on the physical build? I'm really interested to see how it performs 'in the brick'...

23 minutes ago, Attika said:

By the way is there any plan to turn this into plastic? (I know, it's to much pressure from us but great power comes with great responsibility )

I want to build during the days around Chistmas, so that's why I'm eager to get the chassis done, in concept that is. Here are a few more renders, a top view and some details in the gearrack and steering link area.

26 minutes ago, Attika said:

Let me highlight your laziness: The tread on the wheels point different direction on each side. (copy-paste?)  

Haha, yeah a copy and paste mistake. The tires on the left of the vehicle are correct.

[Attika]

17 minutes ago, Didumos69 said:

 

I want to build during the days around Chistmas, so that's why I'm eager to get the chassis done, in concept that is.

So what is the plan between now and christmas then? 

 

19 minutes ago, Didumos69 said:

Haha, yeah a copy and paste mistake. The tires on the left of the vehicle are correct.

Yeah, was kinda obvious, but a good grip to mock a perfectionist. 

 

Question: On the top view the rear axle looks a bit funny. Like it is missing something behind the XL motors. There is a 5L axle with a half bush in the middle of the nothing. Or is it the pespective what is tricking my eyes?

[Didumos69]

3 minutes ago, Attika said:

Question: On the top view the rear axle looks a bit funny. Like it is missing something behind the XL motors. There is a 5L axle with a half bush in the middle of the nothing. Or is it the pespective what is tricking my eyes?

Sorry, the rear axle still needs to be designed, what you see are just a few placeholders.

[Attika]

14 minutes ago, Didumos69 said:

Sorry, the rear axle still needs to be designed, what you see are just a few placeholders.

Fair enough. You've got plenty of time till xmass. It was just suspicious, as the rest of the chassis is so dense like it was built by Didumos69... ooops. 

[Didumos69]

10 hours ago, Attika said:

Fair enough. You've got plenty of time till xmass. It was just suspicious, as the rest of the chassis is so dense like it was built by Didumos69... ooops. 

? Yeh, I know. I guess the current lightweight state of the rear section is more your style... oops ? (a style I sometimes envy btw). 

Edited December 8, 2018 by Didumos69

[pagicence]

Have you consider using Claas tires on Porsche rims? I think they will look cool on the vehicle that has a car like body (like Zarooq SandRacer). Also how do you feel about using third party tires? A good thread pattern on a tire can make a vehicle look 20% cooler and meaner.

[Didumos69]

2 hours ago, pagicence said:

Have you consider using Claas tires on Porsche rims? I think they will look cool on the vehicle that has a car like body (like Zarooq SandRacer). Also how do you feel about using third party tires? A good thread pattern on a tire can make a vehicle look 20% cooler and meaner.

The Porsche rims are no option, because they cannot be attached to the turn-table based wheelhubs. Also, I'm quite sure CLAAS tires would deform over time, causing them to no longer fit the rims for which they have been intended. However, I certainly consider using 3rd party tires and I agree it can make a big difference. Something with the dimensions of the CLAAS tires, so people can always decide to use CLAAS tires instead of 3rd party tires.

Edited December 8, 2018 by Didumos69

[Zerobricks]

I think you could drastically increase the efficiency of the system by simply uisng U-joints to cross two side of the drives. It may not be as elegant as 3x16 tooth gears, but it would be more efficient.

[Didumos69]

19 hours ago, Zerobricks said:

I think you could drastically increase the efficiency of the system by simply uisng U-joints to cross two side of the drives. It may not be as elegant as 3x16 tooth gears, but it would be more efficient.

Thanks for the suggestion! Are you saying that because it reduces the number of gear meshes in general or specifically because it avoids using a clutch gear? Apart from that, I don't see a way to cross the drive lines with only 2 U-joints while making sure they arrive at the same height. One driveline would have to cross with 2 U-joints and the other would have to make a kind of bridge with 3 U-joints. Don't know if this will really be more efficient.

[Didumos69]

I did find a way to avoid the clutch gear by using normal gears. A perfectly fitting 24t-16t mesh. The auxiliary axle with the 16 gear is 1.5L lower, which makes a center-to-center distance with the left and right drivelines of sqrt(2x2 + 1.5x1.5)L = sqrt(6.25)L = 2.5L (actually a scaled Pythagorean (3,4,5)-triple).

And here is a close-up cut-away of the gearrack assembly underneath the shifting knob-wheels:

And some cut-aways of all the functions:

Edited December 9, 2018 by Didumos69

[Aleh]

Very complex project! Glad to follow it!

[Didumos69]

Update: Made some renders of the current state of the chassis. The rear axles have stabilizing links that are placed in such a way that there is slight tension. This reduces lengthwise play in the A-arms to a minimum. Now I'm at the point of ordering parts and start building and testing.

Edited December 14, 2018 by Didumos69

[agrof]

Holy shiny tires! This is looking more complex I could ever imagine! So, I can not really add more than a thumb up for now, maybe if You reach the rear light are, I will be back.  

[Didumos69]

On 12/13/2018 at 6:38 PM, agrof said:

shiny tires

Fixed that