[HELP] Number of Axles

[aminnich]

Hey guys,

I know that trucks have more axles to distribute the weight of what they are transporting. That is why some lowboys and what not use a Jeep, this gives more axles. So I am wondering if you think it will have a mush great effect if you would add more axles to a heavy transport vehicle with LEGOs.

I am torn between adding another powered axle on my truck to add more power, so depending on the answers I get, is what I will do.

Also, what if I had a 4 axle truck (3 in rear) but only powered 2 of the three rear, idk.

[twoofive]

i recently rebuilt my 8285 tractor form original single drive axle to dual rear axle , also lenghtened another 8285 to triple dual wheel axle in the rear.

my crane is also rebuilt from 5 axle to 7 axle

from what i noticed is that the more axles are powered/driven, the less crunching of gears and fiffs occours;-)

[aminnich]

ok, seems like a good idea.

I am powering each wheel independently with L motors. I just do not know if I will have to power all three axles, requiring 6 L motors just for drive!!

[BobSmithHello55]

You may end up in a vicious feedback cycle, whereby you add ore motors which can mean more weight, and then you need more powered axles with even more motors, which leads to more weight....

[aminnich]

weight is not a problem, as of right now (two powered axles) I move along very well, with four battery boxes for weight, two battery boxes for power, 4 L motors, and a chassis. Weight is not a problem

[Blakbird]

Heavy trucks have many axles not to make the truck drive better. They have many axles because the road will be damaged by too much load at one point (concrete will crack). I don't think you will get better performance by adding axles.

[nerdsforprez]

For what it is worth, i built a large and heavy crane (~4,000 pieces),

and although powered only two axles, only did so with one XL motor. Now, given this, I will say that for the purposes of the build it did not need to go fast, so I geared it down to have a lot of torque. What I found is that one XL motor powers my 8 axle crane just fine... again slow, but then that is not a problem. It is not an off-road crane.

Unless you plan on going off-road with your truck, or want excessive speed, I am not sure that you will have to put so much power in your model. Two L motors, powering 2 or 3 axles (doesn't matter) should do the trick. Sheepo's (4,000+) mustang is powered by two L motors, which seems to move just fine (for a Lego model). Unless you want your truck to go faster, and have it geared properly, again, don't think that you need it to have so much power.

Now... if this is a trial truck... then just disregard everything I have just said

...Sheepo's (4,000+PIECES) mustang .....ooops.... forgot to add

[aminnich]

Both suggestions sound good. The truck is a semi truck. I was planning on the truck to move around fairly quick. Have the L motors geared down 1:3. each independently powering a wheel.

Just to give you an idea of what it will be pulling. I built a trailer for the 42030 loader. As of right now just with the chassis with the 6 L motors, it pulls it, but looses a lot of the power it had.

[andythenorth]

You may have very high friction on the trailer axles, technic axles make for poor bearing surfaces. Adding more axles might help reduce the binding if that's a problem. But it might not be.

Also, adding a very tiny amount of olive oil to the bearing surface of technic axles can make a big difference. Olive oil is safe on plastic, except it can collect dust over time and make sludge (so don't add much). A lot of sets perform better with olive oil.

Bricklink lists 42030 at around 3.5kg. With similar axles, and 4 L motors I clocked about 1.8km / hr with a 7.2kg load. But that was testing with the trailer from a kid's ride on toy, which has easy-rolling 30cm wheels on metal axles What does your trailer weigh?

Are you on carpet or solid floor? Carpet sucks for PF performance.

Edited January 12, 2015 by andythenorth

[aminnich]

The trailer is just bare bone right now, still have to add some pf to it, but I will weigh it out once it is done. I did run the chassis on carpet while pulling the heavy load. will hard wood be that much better??

If it gets down to having to use some kinda of lubricate, i will. but id rather not.

[nerdsforprez]

The trailer is just bare bone right now, still have to add some pf to it, but I will weigh it out once it is done. I did run the chassis on carpet while pulling the heavy load. will hard wood be that much better??

If it gets down to having to use some kinda of lubricate, i will. but id rather not.

Going on a hard surface will make a BIG difference. Also, best lubricant is silicone-based lubricant. Olive oil is okay, but silicone spray is better. Commonly used for LEGO pneumatic engines

[aminnich]

I decided just to go with the rear 3 axles all powered. Lots of battery drain though.

[DrJB]

As you and others have pointed to, there are many reasons to decide how many axles. First, for a given truck-trailer, there typically are three types of axles: Steering, driving/driven, and purely load bearing. If you take an 18-wheeler truck/trailer combination, the front axle is for steering, axles 2/3 on the truck are for both traction and load bearing, and axles 4/5 on the trailer are only to support the load (not driven and not steerable). Adding more axles is typically done to reduce the tire/road pressure and thus increase the load capacity of the truck. Making more axles driven/powered, will even out the traction force on those axles, for uniform tire wear. Unlike cars, where 4WD has benefits in off-road and bad weather conditions, you rarely (if ever) see trucks with AWD, unless on some specialty vehicles.

Edited January 13, 2015 by DrJB

[Jim]

Heavy trucks have many axles not to make the truck drive better. They have many axles because the road will be damaged by too much load at one point (concrete will crack). I don't think you will get better performance by adding axles.

Interesting. While it sounds very logical, I always assumed it had something to do with the load on the truck itself. Thanks for the insight

[Blakbird]

Interesting. While it sounds very logical, I always assumed it had something to do with the load on the truck itself. Thanks for the insight

Every country has laws which limit the permitted load per axle. In order to operate your vehicle on a public roadway, you need to add more axles to add more weight to avoid damaging the road. You will note that REALLY heavy vehicles (like the CAT 797) that are only for use off road only have 2 axles.

On soft terrain, more axles and/or tires and/or treads also help the distribute the load so you won't sink in.

From a mechanical perspective, it is easy enough to make bearings and axles to handle any load, so adding more axles usually has a non-mechanical purpose. Of course, LEGO axles have no bearings and therefore have a lot of friction, so it is possible that adding more axles may help support a large load, but I doubt it because it also adds more rolling resistance in the tires.

[dhc6twinotter]

I would go with whatever number of axles is realistic for a truck that is pulling a L350 loader. If it were a U.S. truck, I think I would shoot for a four axle tractor (two drive axles) and at least a four axle lowboy trailer. I'm not sure what part of the world you're in, Aminnich, so perhaps cabover trucks and other types of trailers are more common where you are at.

Here in the U.S., most states have a max weight of 80,000 pounds, as well as max load weights for each axle of a truck. It varies a little by state, but for the most part, single axles can carry a max of 20,000 pounds and tandem axles a max of 34,000 pounds. If a driver is at 80k, getting the load right on each axle can be tricky, and most trucks have sliding 5th wheels and sliding trailer axles to help adjust the weight distribution. Spread (or split) axle trailers follow the 20k per axle rule, so weight distribution is easier, but that comes at a cost of greater tire wear and greater susceptibility to tipping over on tight turns. Here in Washington State, we have a max load weight of 105,000 pounds, which is the 2nd highest in the nation. The trucks still have about the same per axle weight limit, so most of the WA based trucks have an additional axle (non-driven) on the tractor and one or two additional trailer axles. Four axle tractors pulling four axle trailers are pretty common here in WA.

Anything over 80,000 pounds (or 105k in WA) requires an overweight permit with the appropriate number of axles.

Just my $.02.

[aminnich]

Thanks for the information, did not know all of that, Thanks. I am from the east coast, so I wanted to build a peterbilt daycab truck. Currently the trailer I made is not accurate for the L350F Loader. So im probably going to make some kinda of lowboy. I have tried making a lowboy in the past (infact i just took it apart), but I could not figure out the detachable gooseneck for the life of me.

So hopefully by the time my truck gets done, i will have a better understanding of the gooseneck.