Help with my first real technic MOC: a Tatra

[Junpei]

I have finally decided to make a real technic MOC, I have made about 5 of them and they were all studded, disorganized and ended up not functioning and looking like crap at the same time (and they all had xl motors!), so I decided I wanted something fast but powerful but not to spend tons of money on RC motors and an RC unit, so I am building a Tatra 6x6 with an XL for every wheel. I know it depends on the overall weight of the vehicle, but I wanted to know if it would be powerful enough with the XL's ungeared driving standard truck trial (9398) wheels. My other question is what kind of shock absorber to use, but I will post pics and stuff tomorrow but I really have a ton of work to do tonight but just so you know I am using the usual swing-arm suspension with the pivot being the two pinholes in the back and the shocks are mounted on the front pinholes and I am using 6,5l shock absorbers and am not sure if there is enough travel although it looks like the camber is about right and sorry for the really really long run on sentence, i will be less busy tomorrow.

[DLuders]

You may get some good ideas from the many Tatras posted on the (inactive) BrickTruckTrial.com website. I would say using a Power Functions XL motor (ungeared) for each wheel will provide PLENTY of power.

[Doc_Brown]

Wow, 6 XL motors! Yes that will be plenty powerful, just don't have the direct drive being affected by the terrain, as it may damage the gearing inside the XL's or put unnecessary wear on them.

Looking forward to the pics!

[jorgeopesi]

You don´t need 6 motors, look what Sheepo can do with only 4 and 8 wheels...

[Junpei]

Wow! Sheepo's Tatra is amazing. But I actually have the motor as the swing-arm right now and am planning to make this without a drive-train.

Edit: I guess Sheepo's Tatra only has 2 knob wheels per axle, I meant gearless.

Edited June 4, 2013 by TwentyLeggedHen

[750ACE]

Just curious why do tatras have the extra piece on the wheel or rim? Is it a type of lock on the real life tatra?

[jorgeopesi]

The Sheepo´s Lizaard is not a Tatra, it has 4 rigid axles. It was an example of the power of "only" 4 XL motors .

[Blakbird]

You don´t need 6 motors, look what Sheepo can do with only 4 and 8 wheels...

True, but most people are not Sheepo. If we were then the world would be a much different place.....

[hrontos]

Just curious why do tatras have the extra piece on the wheel or rim? Is it a type of lock on the real life tatra?

This thing on a real Tatra (and many others) allows you to control air presure in tires. Driver can decrease and increase the pressure as needed. It should even capable to keep even deffective tire inflated so that vehicle can move on.

[jorgeopesi]

True, but most people are not Sheepo. If we were then the world would be a much different place.....

You are right Blackbird but in this example Sheepo uses a simple configuration of a trial truck, easy to see and learn from it, unfortunately I can not say the same for the suspension .

[Junpei]

Here are two pics: The suspension and the battery. 18 AAA batteries are going to cost a fortune!

Damn the links don't work! I am creating a brickshelf now, sorry.

[Technyk32231]

Wow! Sheepo's Tatra is amazing. But I actually have the motor as the swing-arm right now and am planning to make this without a drive-train.

Edit: I guess Sheepo's Tatra only has 2 knob wheels per axle, I meant gearless.

It's not a Tatra. It's Sheepo's custom design with pendular suspension.

[Junpei]

Sorry it has been 4 days, I just got out of school yesterday. Here are the pics: http://www.flickr.co...s/97116741@N05/

Edit: I am not sure if a standard TT wheel will fit around the whole thing if I remove the portal axle, but I will try if I order them. What am I going to do about the batteries? All 18 rechargeables will cost 100 dollars!

Edited June 8, 2013 by TwentyLeggedHen

[pint14]

Gear reduction will be 1:1? :O

[Saberwing40k]

I'm kind of wondering why you decided to use AAA battery boxes. I mean, the AA boxes provide more power, and for longer. I'm also more than a little bit baffled by your decision to only use 1:1 gearing in them portal axles. And lastly, your truck is going to look absolutely preposterous, due to it being far, far wider than it should be in relation to the wheels and wheel bases. I'd say just make this a skid steer custom six by six, and ditch the Tatra angle entirely. Or make it chibi.

[Junpei]

I am pretty sure it is the other way around with the battery boxes, the AAA provide more power. I am going to remove the portal axles decreasing the overall width by 3 studs, but if I do that the only wheels that I think will fit around that are PP wheels. So I think I am going to make the whole vehicle itself without the wheels and just put it off until I have enough for PP wheels. Also, will skid steer work on a 6x6?

[The Ghost Racer]

Sorry it has been 4 days, I just got out of school yesterday. Here are the pics: http://www.flickr.co...s/97116741@N05/

Edit: I am not sure if a standard TT wheel will fit around the whole thing if I remove the portal axle, but I will try if I order them. What am I going to do about the batteries? All 18 rechargeables will cost 100 dollars!

What!? 100$? Where I live 4 Sony AAA rechargeable batteries 1.2V 3800 mAh cost from 6 to 9€, and then about from 8 to 12$

I am pretty sure it is the other way around with the battery boxes, the AAA provide more power.

It depends of the amperage of batteries. Edited July 24, 2013 by The Ghost Racer

[Sariel]

You don´t need 6 motors, look what Sheepo can do with only 4 and 8 wheels...

I would still call it an overkill, seeing as most 8x8 trucks in our Truck Trial races run successfully on 2 or even 1 XL motor. Efficient drivetrain is all it takes. And it can be taken even further, as proven by TT's 8x8 ZIS truck, driven by two MEDIUM motors: http://www.brickshel...ry.cgi?f=444723

I think 2 XLs give you enough torque to move any 6x6 over any terrain. The question is: how efficiently you can put it to use.

Edited July 24, 2013 by Sariel

[MrNumbskull13]

THAT THING RUNS OF 2 M MOTORS?!!!!! NOW THAT'S IMPRESSIVE!!!

I think 2 XLs give you enough torque to move any 6x6 over any terrain. The question is: how efficiently you can put it to use.

How exactly do you make an "efficient drivetrain"?

[Sariel]

You make it simple, prevent body from pressing on it (driveshafts through turntable, etc.) and use grease on most loaded elements such as knob gears. TT got there by basically minimizing the number of high-friction elements in his drivetrain. Of course direct drive is as simple as it gets, but it's neither challenging nor realistic.

[The Ghost Racer]

Uhm, a really interesting thing. another important factor is the weight of the model, the distribution of it and then also the center of gravity. The body can sometimes be a very important factor, as in my Tatra, as it contributes greatly to strengthen the chassis.

Do not forget axles have to be rigid and resistant, integrated with the excellent suspension, to transfer maximum torque from the engine to the wheels, and from the latter to the ground.

To talk about the thing seems easy, but in reality it is not at all: you have to thoroughly study your chassis, make several tests trying to improve it, but at the same time to ensure that the final product is similar to the real one on which the project is based. Of course, creating an imaginary trial truck it may be easier in some respects, including greater freedom of style in building the chassis and body, but all this freedom can become a problem since we do not know where to start to build the chassis, and also if you are not familiar with the strengths and weaknesses of various types of transmission, suspension, axles and chassis configurations vaire becomes a problem make efficient our trial truck.

Conclusion: to study in depth the characteristics of the trial truck from which you want to get ideas, evaluate their strengths and weaknesses, realize chassis robust and efficient but at the same time light. A solution to excess weight can be achieve in technic bodies rather than studfull.

Edited July 24, 2013 by The Ghost Racer