AutoBacon

[WIP] Building a krAZ 255 6x6 Truck

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6 minutes ago, AutoBacon said:

I decided to trade some solidity for the improved reliability of CV joints. Since the beginning, I was not happy with putting full torque from the motor on CV, so any gear reduction after CV is beneficial, especially as more weight is being added with the cabin. Using 20T also means the female CV end can remain 2 studs long which should address the concerns of ZeroBrick's comment above.

I agree that taking whatever torque we can from CV joints is a good thing to do. That is why I'm looking for opportunities to use new CV joints especially where torque is transferred to whole axle (I found out, that old CV joint/cardans are fine, when they need to drive only one wheel - 30mm rim, even with big tire with aggressive tread like 56mm tractor tires). Your model can have some weight due to brick build style, probably even more than my original KrAZ 255 which is below 1kg. Do you know already what will be the weight of the model? Based on simulation even?

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27 minutes ago, keymaker said:

I agree that taking whatever torque we can from CV joints is a good thing to do. That is why I'm looking for opportunities to use new CV joints especially where torque is transferred to whole axle (I found out, that old CV joint/cardans are fine, when they need to drive only one wheel - 30mm rim, even with big tire with aggressive tread like 56mm tractor tires). Your model can have some weight due to brick build style, probably even more than my original KrAZ 255 which is below 1kg. Do you know already what will be the weight of the model? Based on simulation even?

Hmm, this is an interesting point, perhaps I could swap the CV to each axle for the new CV, and shorten the female end from 3 to 2 studs, I like this idea. Regarding weight, I think it should be not that close to your original model. Currently, the chassis with motors and battery is 475g, and stud.io measures the fenders/cabin as 170g. Say we account for up to 100g of accessories such as storage boxes and cabin bench seat, I think the total weight should be around 750g.

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22 hours ago, AutoBacon said:

Hmm, this is an interesting point, perhaps I could swap the CV to each axle for the new CV, and shorten the female end from 3 to 2 studs, I like this idea.

This is exactly what I was going to suggest. Shorter version of the new CV joint would be very useful to have, but luckily that's something really easy to manufacture at home :) I think you have space to replace all of them with shortened new ones.

Regarding the front diff, it is indeed probable that it will skip, but the fact that the truck has 3 axles and most pressure would probably go on the rear ones might save the day.. By the way, did you glue together some connectors there?

What do you mean when you say the motors can be fine controlled with analog control? Is it just that the MouldKing system supports proportional control? Or is there something more tricky happening? By the way, how easy is it to set the steering straight? It seems a little bit fast for me for that.

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On 1/10/2023 at 10:17 AM, gyenesvi said:

This is exactly what I was going to suggest. Shorter version of the new CV joint would be very useful to have, but luckily that's something really easy to manufacture at home :) I think you have space to replace all of them with shortened new ones.

Regarding the front diff, it is indeed probable that it will skip, but the fact that the truck has 3 axles and most pressure would probably go on the rear ones might save the day.. By the way, did you glue together some connectors there?

What do you mean when you say the motors can be fine controlled with analog control? Is it just that the MouldKing system supports proportional control? Or is there something more tricky happening? By the way, how easy is it to set the steering straight? It seems a little bit fast for me for that.

I have since replaced the CV joints and it has been a massive improvement. Now the weakest component is the front diff. But you are correct, most pressure goes to the rear axles, so it is rarely an issue. So far I have glued zero parts, however, if the additional weight of the cabin causes an issue I may glue some of the front axle parts, I have not decided yet :D Regarding Mouldking battery, it is simply a physical controller with proportional speed control, and it allows for fairly precise movements, I agree it is a little fast for steering particularly when driving, but it is definitely usable and quite easy to set straight, and I think the amount of space saved is worth it. (in the video I was mainly going full left to right due to the small desk space hehehe)

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