Wheel slippage

[aminnich]

Hey guys,

I'm working on a small project just for something to do other than homework all the time. figure I would try and build it. I'll share it once it is completed :) but anyway, it is a semi truck with a heavy load, but the load is quite heavy and I get a lot of wheel slippage on the rear axles (truck is only RWD)

I could make I a 8x8 truck but I'd rather fix the problem another way, but I'm not sure how. I will try to make the truck an 8x8 tomorrow, but I'm not sure that will fix my problem.

Any thoughts??

[Milan]

Post a picture.

[dr_spock]

How is the weight of the heavy load distributed? You may need more downward force (weight) over the driving wheels to increase traction. This is the case with LEGO train motor when wanting to pull a longer heavy train.

Also what kind of surface are you driving on?

[aminnich]

I tried just adding battery boxes on the king pin (centered over driven axles) but no difference. I'm driving it on my basement floor, concrete. Would those be wheel slippage if their wasn't enough power? Could the load just be too heavy?

[allanp]

We need pictures.

[aminnich]

I'll post some pictures today

[dr_spock]

A video might be better for motion type problems.

[andythenorth]

Which tyres? The 62.5 ones (as used in 42009 crane etc)? Some tyres are harder than others and lose traction faster.

Got any suspension on the driven axles?

How is it driven? One motor per wheel, or with diffs?

[aminnich]

If i video is needed, I can try and take one.

Which tyres? The 62.5 ones (as used in 42009 crane etc)? Some tyres are harder than others and lose traction faster.

Got any suspension on the driven axles?

How is it driven? One motor per wheel, or with diffs?

I am using the 62.5 tires. I have not done any experimenting with different drive methods, it was late last night when i got a different part of the MOC done. I will be working on modding the truck later to fix this wheel slippage problem

The truck im using this is one...

http://www.eurobricks.com/forum/index.php?showtopic=120229

EXCEPT, the chassis is a bit shorter. But these pictures should give you guys a good idea of what the truck has to offer.

[dr_spock]

Does your basement have a dusty or dirty floor? Loose particles sticking to the tires can cause them to lose some grip.

[aminnich]

I dont know about you, but I dont dustmy basement But, yes their is a lot of dust of the floor, but not enough to coat the wheels in a layer of dust

Edited February 6, 2016 by aminnich

[deehtha]

My guess is that you have too much weight on the front and not enough over the drive axles.

[aminnich]

Alright so I took some pictures, I was not really sure how to show the issue with a picture, but if a video is needed, i can try it.

The two red boxes are about the weight of the load the truck would be carrying. Keep in the mine the jeep/dolly is in the first stages of building, very rough build.

I think my first approach to fixing this will be to up the horsepower (add more XL motors) and drive each axle separately. And if that does not work, I will have a set of XL motors drive the front 2 axles and the other set of XL motors drive the rear axles giving me an 8x8 truck.

[Edwin Korstanje]

I think the problem is that you have not geard down the drivetrain and with two XL motors direct to the backwheels with not much weight on the back on a slipery floor you get this problem

[Milan]

Its quite simple.

Most (all) of the weight on your truck is concentrated on the first two axles, leaving it to the back tires to have very little pressure to the ground, thus unable to deliver power to the ground.

Very common problem on the real truck on slippery surfaces when they are unloaded, or in case of tractor trucks without trailer attached - they get easily stuck on slippery surfaces.

Solution is NOT to add more power, but to move more weight to the back wheels. You can just put those red storage boxes above truck's back wheels and problem will be solved.

So, it is best to make a trailer that will rest on the back of the truck - the usual semi trailer, where the load will be spread to the both sections of the trailer: to the front (where it rests on the truck) and to the back (where it rests on the trailer wheels)::

Right now, load on the trailer is put entirely onto the trailer wheels, and not a bit onto the truck, which causes slippery.

Edited February 6, 2016 by Milan

[deehtha]

The way your trailer is now, it does not transfer very much weight to the tractor unit. I would making the wheels in the trailer a bogey so that the weight is transfered to the tractor unit.

Right now, your drive axles have the least amount of weight on them.

[aminnich]

Lets say the jeep of the real trailer is the actual trailer and the red boxes are the load. I still have the same problem as if the real part of the trailer is attached to the jeep.

I understand what you guys are saying about the distribution of weight to the rear axles, but adding more weight right on the king pin of the trailer still does not do anything to help with the wheel slippage.

[Milan]

I understand what you guys are saying about the distribution of weight to the rear axles, but adding more weight right on the king pin of the trailer still does not do anything to help with the wheel slippage.

Just put a few books to the king pin and try.

[motomatt]

Solution is NOT to add more power, but to move more weight to the back wheels.

Milan is spot on. Has nothing to do with the power or gearing. The weight of the trailer is not getting loaded onto the truck's fifth wheel because of the angle of the liftarm(s) connecting the trailer body to the king pin. Try to remove one set of trailer tires to leave it with one working axle and you should see it working.

To fix it, you need to somehow lower the height of the liftarm going from trailer to king pin (or raise height of fifth wheel... by inserting "Technic bush 1/2 smooth" to kingpin axle) so that the truck's axles end up bearing more weight. You also need to consider that there will be considerable flex in the same liftarm... this will cause the trailer's front-most axle to bear more load and the rear-most axle to tend to float in the air.

Edited February 7, 2016 by motomatt

[rollermonkey]

Heck, the way those boxes are loaded on that trailer, I'm surprised the wheels aren't actually lifting up off the ground.

Ask any professional trucker, weight distribution is everything.

Putting a couple battery boxes over the kingpin doesn't offset the fact that too much of the load is just way too far aft of the drive wheels.

[aminnich]

thanks for all the comments today, they are very helpful!!! I decided to rebuild the truck into an 8x8 anyway, even if it doesn't help me with wheel slippage.

Here is the new truck, I didnt get the chance to do wiring an add some detail, but the truck runs very well. The front 2 axles are driven by 2 XL motors and the same goes for the rear 2 axles.

Heck, the way those boxes are loaded on that trailer, I'm surprised the wheels aren't actually lifting up off the ground.

Do you see the beams at the level of the axles They have little of a bend in them... haha Didnt break anything today though!!!

[zux]

Having suspension would also help distributing weight evenly.

[aminnich]

So I got the truck done today. Hooked it up the the load and the wheel slippage has been fixed... but the truck does not have power to pull it. So simple fix, I geared it down for my torque.

Ok so now my problem is a high drop in voltage from the 4 XL motors and Servo all in one receiver. Any thoughts??

[750ACE]

Add a second receiver and second battery box??

[aminnich]

Good idea