Tracked Vehicle Design 1

[BAT666]

Hello everyone,

I along with a group of colleagues have been given the challenge of building a tracked vehicle which must be highly manoeuvrable cross country over various types of terrain; but limited to a maximum speed of 10mph.

The intention is to create a vehicle similar to the Hagglund BV206 using parts of an old bulldozer for the articulated hydrostatic steering mechanism and I am in the process of obtaining a couple of sets used rubber tracks off 1 or 2 tonne JCB type excavators.

We are currently considering how to design the suspension system but have not had much experience in this field and are therefore looking for a few pointers in the right direction; whether it be advice or references to look at.

One of the main limitations we have is that we either have to manufacture the parts ourselves or cannibalise bits off existing scrap vehicles. I therefore see problems arising with finding / manufacturing suitable sprockets, idlers etc. and so would be particularly interested if anyone can suggest any novel approches to overcome this hurdle.

Cheers,

Andy

 

[GregLocock]

The Hagglund is high speed cross country. 10 mph is not high speed. All you really need to do is use mount each pair of road wheels to a hinged beam. No springs, no dampers.

I would buy the drive sprocket with the tracks, and then use an untoothed version of that profile as the road wheels and idlers.

What sort of durability are you looking for? Is this a serious project, or a design and build for a course?



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[BAT666]

Greg,

Thanks for replying with the advice.

The vehicle only really has to survive a weekend of challenges based mainly on manoeuvrability and control and so in theory doesn’t need to be that durable. We won’t actually know any further information about the challenge until the day, but the vehicle will have to be able to traverse varying cross country terrain probably with a hill climb involved at some stage or other.

It only has to go at a slow speed for the competition, but I’m sure once that’s over (and if it survives!) we’d want to try the vehicle again in the future, probably at a slightly faster speed. Therefore, we would like to design it with some form of durability, but not to the extent required for daily use.

Cheers,

Andy

 

[CESSNA1]

BAT666: Typically miltary tracked vehicles have a drive sprocket for the track at the front of the vheicle and a track tensioner on the idler wheel at the rear. The suspension can be torsion bars or other srings that are attaced to the roadwheels. The roadwheels are the elastomer coated wheels that bear against the track that is in contact with the road. The roadwheels are attached to a structure, usually called a roadarm. The roadarm can then be connected to the hull through springs or a torsion bar.

Regards
Dave

 

[GregLocock]

Sure, but they are designed for high speed cross country. If you google for the vehicle mentioned above you'll see that the suspension is incredibly stiff, so rather than indulge in complexity I suggested a load sharing arrangement.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[edrush]

I'm not sure what Greg is proposing, but I suspect this is a reiteration of his suggestion. Vibration is a killer on tracked vehicles, and two roadwheels connected to a single structure with the structure able to pivot freely should be an effective defense if the two road wheels are spaced out of phase with the track spacing.

Rubber torsion bars are inexpensive and if you mount the dual road wheel structure to the torsion bars then you have a suspension which can also address low frequency bumps. These torsion bars are fairly common on trailers.

Pneumatic tires at low pressure could be a relatively effective suspension also.