SUSPENSION SYSTEMS IN SEMI-TRAILERS...

Suspension systems in semitrailers can be classified in various types.  

I am not going to blog on the type of suspensions or their classifications but what I am going to bring to the fore here is the inherent advantage of having a properly manufactured suspension systems such as York as compared to the indigenous ones which are so widely used by fleet owners but the following write-up will clear a lot of misconceptions.

The only advantage one can gain from using a indigenous or plate fabricated type of suspension system is that the initial cost is less but 

obviously this cheaper option has a very high maintenance cost.  The transporters who opt for this type of fabricated suspension systems ultimately incur loss.

Reasons for failure of the indigenous type of suspension:

• The general wear tear is more in case of the fabricated type of suspension as compared to York manufactured  suspension because the material of construction of the fixed and move-able joints are all made up of forged steel where as the indigenous suspension components are fabricated out of mild steel plates.
• All the joints in a York manufactured suspension are provided with suitable bush so that the main components do not get damaged in the general course of usage.  During a maintenance cycle only the bushes have to be replaced and the job is done.  However in case of the fabricated type of suspension no bushes are provided.  The mating components are fitted with pin type of bolts directly with out any bush.  In due course of time the joints wear out damaging the main plates and thereby causing  play in the joints.  This results in misalignment and tyre wear & tear.  The only option during repairs will be to replace the primary supporting plates which is a costly option.
• In case of York suspension the balance rod has an option for adjusting its lengths so that alignment can be done in-situ, whereas the indigenous suspension have fixed type of balance rods where no adjustment is possible.

I hope this write up will throw some light on the suspension systems to be used so that cost cutting can be done and will help the transporter choose the right type of suspension system especially because there is stiff competition and therefore it is important to take into consideration the running and maintenance cost if we really have to cost effective ........ competitive!!!


Regards,

JAGDISH S KOLUR

Partner - BELCO ENGINEERS

Telefax: +91-22-27423841

Mobile:  +91-9819076201

E-Mail:   jagdish@belcoengineers.com

Reinforcing Primary Members In Semitrailers

The topic I have taken today is very important and relevant.  The manufacturers have to understand that all approved designs take into consideration the rated load to be carried and also a factor of safety is added along with the corrosion allowance depending on the climatic conditions of a place where the fleet is to be operated.

This results in a structure which is optimal in weight and the transporter also ends up getting more payload for a prime mover of a particular capacity.  But this market of manufacture of trailers is highly competitive and is also customer driven.  Sometimes the design of a vehicle is altered to suit the customer's whims and fancies flouting all engineering norms. 

A case in point is if we consider the transporters operating over dimensional cargo with over load.  They insist that the primary member be reinforced with an additional flat which is welded on the bottom flange of the main beam.  The point I am trying to make is here is that the flat is welded in such a location that it does not affect the moment of inertia in any way, moreover the thickness of the flat welded for reinforcing is three times the thickness of the bottom flange or the primary members.  After welding such a flat to the beam it only results in increase in stresses due  to heavy welding.  Failure due to heat affected zone is evident and the purpose is defeated!!  A classic example of failure is shown in the pictures above.

This factor must be considered by the transporters because it affects the rated payloads and the fabricator ends up using more steel without acheiving the objective of strengthening.

REINFORCEMENT OF PRIMARY MEMBERS AT OUR WORKS

JAGDISH S KOLUR

Partner - BELCO ENGINEERS

Telefax: +91-22-27423841

Mobile:  +91-9819076201

E-Mail:  jagdish@belcoengineers.com