Ground Vehicle Transport

[Moesly_Armlis]

Ground Vehicle Transport

With a new wheel model upcoming I wanted to try building a vehicle that could transport equipment over land, sea, air and space.  Seems the land part has given me the most problems so far.  The vehicle pulling the trailer will start to sway then rotate and eventually lose control.  During a test run it some how made it to 28 m/s and now after tweaking a few things the design cannot manage to go over 10 m/s until it twists upon itself and rolls over.

The jet engines are used to pull the trailer and if the motorized wheels are used the results are much worse.  I have rechecked all the wheels using the rotate gizmo in absolute mode and certain they are aligned.  The interesting observation is that if I push the trailer in reverse using the drive wheels the speed sustained is 18 m/s and everything stays straight.

Looking for some advice on improving this design.  The centre of mass is what I am suspecting is causing the issues and am about to try altering the position.  Should the engine have more or less mass since the weight of trailer is 21 tonne?

 

 

[Geschosskopf]

Hmmm....  The guy to talk to about pulling trailers is @Overland, the land-train guru.  However, I have a few suggestions.

First off, I see that the docking port attaching the tractor to the trailer is at a 45^ to the vehicle's centerline.  I would certainly change that so that it's inline.  Docking ports, especialy the smaller ones, are notoriously wobbly, and by having it at an angle to the direction of the applied forces, you're introducing multi-axis wobbles.

Also, I'd lock the gimbals of the jet engines.  I really hate KSP gimbals because they're so prone to overcorrect, they usually just introduce self-reinforcing oscillations.  And if you combine that with the wobbly problem from the angled docking port, I'm sure that will cause problems.

Those "ruggedized" rover wheels are also troublesome and have a long-known habit of grabbing the terrain and flipping the vehicle.  So you might want to use another type of wheel.  Or try @Claw's Stock Bug Fixes, which has a thing that addresses various wheel problems.

Another issue you might be having is that the high CoM, combined with the narrow width compared to height, is causing the trailer to lean left and right any time there's a slight course change.  This course change can come from either your input, SAS's steering input to hold the desired course, or changes in ground slope.  And all this will be amplified by the docking port wobble, whether the port is angled or inline.  In any case, when the trailer leans, its aircraft landing gear will be touching the ground on at a slight angle.  And as any spaceplane builder will tell you, this usually results in severe swerving and flipping out.

[Moesly_Armlis]

@Geschosskopf

Thanks for the reply.  The SAS is not used and the Juno engine has no gimbal.  Your suggestion about the high COM does want me to investigate that.

The most confusing part to me is that the vehicle will travel in reverse using the motorized wheels with no issues and a speed of 18 m/s is sustained.  Thinking of reversing the jet engines and calling it a day.

[Overland]

Try using the regular sized docking port,  that tiny one actually physicly pulls away from the part its attached too and rubberbands under load causing problems.. They also tend to push into your tow vehicle under braking

They made the docking ports more rigid though in the updates so where the regular docking port used to articulate its now more solid.. Good for space stations.. Bad for us

I generally use truss adaptor..then a tiny truss and onto that the docking port..it gives enough articulation with decent auto return centering

Also the design you have with the ports angled.. Generally parts wont rotate as such but flex side to side enough to articulate.. The 44 class in my signature being a good example.. Everything works better being level

Sadly though there limits to what can be done stock because of the wheel physics

30ms is dangerzone for anything articulated. 25ms is a good cruise

Lastly for snaking recovery a few rcs ports with SAS and RCS enabled momentaryly should bring it back into line for the trailer

Hardware wise.. Joystick or wheel is best..keys are too harsh..a wheel also makes drives enjoyable

The load is rather big though..maybe split between two trailers..3 or.. 4

Then you can call it a train.. Then much awesomeness will follow

At this level though powered or alternate powered axels per trailer is a personal choice

[Moesly_Armlis]

On 2/21/2016 at 0:06 PM, Geschosskopf said:

Those "ruggedized" rover wheels are also troublesome and have a long-known habit of grabbing the terrain

After changing the tires everything has improved greatly.  Stability is no longer an issue.  The ruggedized rover wheels I am hoping are fixed in the next update.

The vehicle made it to the beach cruising at 20 m/s with no problems and top speed was 30 m/s.  So very pleasing when things work as intended.  Thanks for answering this issue.
 

 

 

Made me so happy decided to add two more containers just to see what would happen.  Very surprised the vehicle was so stable just lacking thrust.  Made it to 20 m/s on flat terrain and I stopped the train before trying to go uphill.

 

 

 

On 2/21/2016 at 2:05 PM, Overland said:

Try using the regular sized docking port,  that tiny one actually physicly pulls away from the part its attached too and rubberbands under load causing problems

The angle was the result of experiments and for a while it seemed to help.  The hitch, docking port is now vertical and have zero issues. Have to agree with you about trying to steer with the keyboard and will need to dig out my G25.  Thanks for your input. 

Question to you @Overland .   Do you have specific routes that you have surveyed to provide a level grade for train travel?  With the upcoming update I am very interested in toying with the new wheel mechanics.

[Overland]

Its great to see another driver  KSP might not be no european truck simulator but kerbins size and beauty makes a challenging and worthy drive

Your using jets I know but if your using modded stock wheels or stock alone then install this..it adds sounds to the wheels

 

If you going to use a wheel.. You can use the accelerator and brake naturally..youll hear the wheels spool up nicely.. Having wheels as primary motive power or for starting jet propelled power is always great . In my earliest trains jets were primary power and wheels used at low speed.. Its a great way to start and enjoy kerbins beauty

 

Routes for my trains is a strange thing as sometimes from update to update once flat ground becomes an upgraded green stormy sea.. At the moment im going roughly coastal with inland jaunts.. Avoiding any darker areas of ground.. Still it pays well to stop every 10km to plan the next steps with the map view.. No science to it... Just careful driving

EDIT: one important thing for any driver... Music .  Put some on .. Let it become part of the experience:)

Edited February 23, 2016 by Overland