Basic Trailer Frame Analysis and Tow Ball Weight

[kendall.dunnS93DA]

Hi All,

I have been tasked with designing a trailer that is able to carry certain components of varying weights and have completed a chassis. I have uploaded the base chassis in the zip file and have some questions regarding loads and analyzing the results. 

• Does Inventor automatically take into account the weight of the frame acting at the COG when running the simulation?
• The location where the axle attaches to the chassis will have pinned constraint to represent wheels, would the location where the tow ball goes also have a pinned constraint??
• I have components going in the red circled sections, what would be the best methods for simulating those loads, given the locations of the beams and nodes, for instance, if there was a generator weighing 500 kg going at the back, I would put a single point load in the centre, or split the weight into 3 continuous loads acting at the back of the trailer.
• With just the weight of the frame, would the Fy forces in the results sections be the best estimation of the tow ball weight (I have inserted a "probe" at the tow ball location to get an accurate estimation).
• Finally, what is the best workflow when designing and analyzing frames in Autodesk Inventor?

[JDMather · Accepted solution]

https://www.youtube.com/watch?v=1IV2kFkgBRc&list=PLp5izJt_zvN0KUccGh5OrgbNTZ_c4vYxs&index=12

[kendall.dunnS93DA]

Hi @JDMather 

Thanks for the link to that helpful video. Was a great watch and have subscribed to the channel. As informative as the video is, the one parameter I am interested in is the tow ball weight. Could you perhaps elaborate on how I would determine this parameter within the simulation environment?

[JDMather]

@kendall.dunnS93DA 

I thought that was covered in the video?

[pcrawley]

See "Reaction Forces" at about 15:30 into the video 🙂

Excellent video @JDMather - thank you.

Only one other comment:  You probably want 4 points to represent the axle position.  I know the axle is a single shaft, but it connects to the chassis at 4 points (the ends of the springs) thereby spreading the load on those main lengthwise rails. 

Does Inventor automatically take into account the weight of the frame?  Yes (make sure you include Gravity as a load on your simulation).

On a small "light trailer" like this, the reaction force at the tow ball should be about 10% of the gross mass of the trailer including its load.

[kendall.dunnS93DA]

Hi @pcrawley,

I must have missed that bit in the video, thanks for highlighting this and thanks @JDMather for the video.

For a single axle trailer like mine, I am certain that a single pinned constraint on either end of the chassis is sufficient enough to simulate how the trailer frame will deform around the axle.

This is confirmed in the youtube video whereby @JDMather uses 2 pin constraints on either end as opposed to 3 for dual axle leaf springs (see below)

[pcrawley]

Sorry, I meant 4 in total - 2 per side as shown in the video for conventional single-axle leaf springs.  I should have been clearer with my explanation.  Your simulation only shows 1 per side - which (as you say) should give you adequate results if you only want the reaction force on the tow-ball.

I use 2 per side for leaf-spring suspension designs, and 1 per side if I use this suspension: Silent-Ride Trailer Suspension – Timbren (It's significantly better than conventional leaf springs for many reasons.)