Why do trailers have an axle connecting the two wheels?

Why not just attach the wheels on either side independently?

party_pants said:

Why do trailers have an axle connecting the two wheels?

Why not just attach the wheels on either side independently?

simplicity and strength, wheels track same also, probably full length axle offers some bending ability also, some useful flex transferred into longer part between wheels

a solid short axle requires quite a lot of support

transition said:

party_pants said:

Why do trailers have an axle connecting the two wheels?

Why not just attach the wheels on either side independently?

simplicity and strength, wheels track same also, probably full length axle offers some bending ability also, some useful flex transferred into longer part between wheels

a solid short axle requires quite a lot of support

This thread is now closed.

transition said:

party_pants said:

Why do trailers have an axle connecting the two wheels?

Why not just attach the wheels on either side independently?

simplicity and strength, wheels track same also, probably full length axle offers some bending ability also, some useful flex transferred into longer part between wheels

a solid short axle requires quite a lot of support

and leaf springs, it just sort of says put an axle right across, what the leaf springs are saying, support me please axles

captain_spalding said:

transition said:

party_pants said:

Why do trailers have an axle connecting the two wheels?

Why not just attach the wheels on either side independently?

simplicity and strength, wheels track same also, probably full length axle offers some bending ability also, some useful flex transferred into longer part between wheels

a solid short axle requires quite a lot of support

This thread is now closed.

chuckle

captain_spalding said:

transition said:

party_pants said:

Why do trailers have an axle connecting the two wheels?

Why not just attach the wheels on either side independently?

simplicity and strength, wheels track same also, probably full length axle offers some bending ability also, some useful flex transferred into longer part between wheels

a solid short axle requires quite a lot of support

This thread is now closed.

Noice.

transition said:

a solid short axle requires quite a lot of support

Is a solid short axle even necessary? Surely there must be another way of making a solid fixed inner part of the wheel with an outer bit that rotates over it.

party_pants said:

transition said:

a solid short axle requires quite a lot of support

Is a solid short axle even necessary? Surely there must be another way of making a solid fixed inner part of the wheel with an outer bit that rotates over it.

stub axles. still need suspension.

The common axle & leaf spring thing is used a lot because it’s the cheapest way of doing it. To a degree, leaf spring self-damp their motion so you can often get by without needing dampers (incorrectly known as shock absorbers) but with independent wheels & coil springs you need dampers.

Slight thread hijack but related.

Why do trucks continue with front beam suspension when cars had independent front (usually double wishbone) suspension decades ago?

Kingy said:

Slight thread hijack but related.

Why do trucks continue with front beam suspension when cars had independent front (usually double wishbone) suspension decades ago?

cheap and easy to maintain. quite a few drawbacks though.

JudgeMental said:

Kingy said:

Slight thread hijack but related.

Why do trucks continue with front beam suspension when cars had independent front (usually double wishbone) suspension decades ago?

cheap and easy to maintain. quite a few drawbacks though.

Yeah, when I’m going around a corner and one front wheel hits a pothole, both front wheels dance across the road, completely ignoring my steering wheel inputs as I get closer to the trees whistling past the rear view mirror, and my sphincter begins to suck a hole in the seat cover.

Hence my question.

Kingy said:

Slight thread hijack but related.

Why do trucks continue with front beam suspension when cars had independent front (usually double wishbone) suspension decades ago?

Cheap & strong.

Spiny Norman said:

Kingy said:

Slight thread hijack but related.

Why do trucks continue with front beam suspension when cars had independent front (usually double wishbone) suspension decades ago?

Cheap & strong.

Yeah, just like my “new” car:

Why don’t cars still use it?

Kingy said:

Spiny Norman said:

Kingy said:

Slight thread hijack but related.

Why do trucks continue with front beam suspension when cars had independent front (usually double wishbone) suspension decades ago?

Cheap & strong.

Yeah, just like my “new” car:

Why don’t cars still use it?

Because the kinematics of using a live-axle front end are terrible. It’s liveable on the rear though.

Spiny Norman said:

Kingy said:

Spiny Norman said:

Cheap & strong.

Yeah, just like my “new” car:

Why don’t cars still use it?

Because the kinematics of using a live-axle front end are terrible. It’s liveable on the rear though.

Hence my question about trucks, new trucks still have a front beam axle, which is terrible for steering.

JudgeMental said:

Kingy said:

Slight thread hijack but related.

Why do trucks continue with front beam suspension when cars had independent front (usually double wishbone) suspension decades ago?

cheap and easy to maintain. quite a few drawbacks though.

Wouldn’t it tear up the roads every time the truck turns? Because of horizontal shear between the tyres and the road.

I’ve been noticing lately how potholes form at intersections and turning points.

Kingy said:

Spiny Norman said:

Kingy said:

Yeah, just like my “new” car:

Why don’t cars still use it?

Because the kinematics of using a live-axle front end are terrible. It’s liveable on the rear though.

Hence my question about trucks, new trucks still have a front beam axle, which is terrible for steering.

Yes, but it’s strong & cheap, and trucks don’t (shouldn’t!) approach traction limits when cornering. They obviously do at times, but I’d guess that it’d deemed to be an acceptable risk.

mollwollfumble said:

JudgeMental said:

Kingy said:

Slight thread hijack but related.

Why do trucks continue with front beam suspension when cars had independent front (usually double wishbone) suspension decades ago?

cheap and easy to maintain. quite a few drawbacks though.

Wouldn’t it tear up the roads every time the truck turns? Because of horizontal shear between the tyres and the road.

I’ve been noticing lately how potholes form at intersections and turning points.

It’s the same tyre-road dynamics no matter what type of suspension is used. Unless you have a very odd type of suspension the wheels is going to be close to vertical when cornering on the vast majority of cars & trucks.

mollwollfumble said:

JudgeMental said:

Kingy said:

Slight thread hijack but related.

Why do trucks continue with front beam suspension when cars had independent front (usually double wishbone) suspension decades ago?

cheap and easy to maintain. quite a few drawbacks though.

Wouldn’t it tear up the roads every time the truck turns? Because of horizontal shear between the tyres and the road.

I’ve been noticing lately how potholes form at intersections and turning points.

I’ve noticed this too

I’m thinking shear forces from vehicles turning / braking

Its always made me wonder if putting some concrete base down with teeth set into it so the asphalt meshes with the concrete teeth could work? Or maybe rods sticking up from the concrete to mesh with the asphalt ? Or maybe try and add something to the asphalt to improve cohesion / adhesion of the asphalt ?

I’d doubt if suspension would really do anything. If the vehicle changes direction or velocity in anyway the road will need to apply force in the opposite direction.

You need to use better asphalt

Maybe making tyres wider would help ( or more wheels)

More rolling resistance BUT better grip and it spreads the load on the road.

wookiemeister said:

I’d doubt if suspension would really do anything. If the vehicle changes direction or velocity in anyway the road will need to apply force in the opposite direction.

You need to use better asphalt

Nope.
If we pretend that the tyre isn’t a spring for a moment, then if we had zero suspension on the vehicle when it cornered the lateral load would be immediately transferred onto the tyre then surface. With suspension, that load is more progressively transferred as the spring compresses over time & distance, thus reducing the point load under the tyre and spreading it along the distance that the suspension is compressing as the vehicle moves as well.

When you turn a corner I suppose the outer wheel and inner wheel do the same amount of work as each other (?). Or is more weight shifted on to the outer wheel but as the outer wheel spreads the work over the greater distance the difference is negated ?

If two vehicles with suspension and no suspension turn exactly the same line the road would need to do the same work on them. If the suspension dampens the response or spreads the work then it means the vehicle with suspension needs more road to turn ?

So changing the shape of the turn of the road is a factor don’t have roads that intersection at 90 deg.

Tyres must have some agreed level of flexibility / spring / torsional strength AND shear strength.

You’d want layers that criss cross ?

As a vehicle turns the tyre must effectively twist from top to bottom

wookiemeister said:

When you turn a corner I suppose the outer wheel and inner wheel do the same amount of work as each other (?). Or is more weight shifted on to the outer wheel but as the outer wheel spreads the work over the greater distance the difference is negated ?

The more the lateral load, the more the other tyre works and the less the inner works.
You can see that in many motorsport videos, where when a car is going around a corner and hits a small bump with the inside wheel, the car will lift up onto the outer two wheels alone for a while.
Or just roll over, whatever.

wookiemeister said:

If two vehicles with suspension and no suspension turn exactly the same line the road would need to do the same work on them. If the suspension dampens the response or spreads the work then it means the vehicle with suspension needs more road to turn ?

Yes, a little.

So … very hard rubber might do more damage to a road compared to a more flexible tyre. As in if you hit a bump more work is done over a set distance than a flexible one

wookiemeister said:

Tyres must have some agreed level of flexibility / spring / torsional strength AND shear strength.

You’d want layers that criss cross ?

No, radial ply tyres work better than crossply types. Crossply tyres started to die out over 40 years ago – But are still used in some areas …. not sure about big truck tyres sorry.

I briefly worked on locomotives ages ago and learnt there’s an interplay between the wheels of the locomotive and the track.

The locomotive wheels were traction controlled to stop them damaging the track

wookiemeister said:

As a vehicle turns the tyre must effectively twist from top to bottom

Yep, though mostly at the bottom.

Spiny Norman said:

wookiemeister said:

Tyres must have some agreed level of flexibility / spring / torsional strength AND shear strength.

You’d want layers that criss cross ?

No, radial ply tyres work better than crossply types. Crossply tyres started to die out over 40 years ago – But are still used in some areas …. not sure about big truck tyres sorry.

I’m reading cross ply is better for 4wd tyres , more rigidity. Radial tyres better fuel efficiency, ride comfort transfer of heat across the tyre is better.

Spiny Norman said:

wookiemeister said:

As a vehicle turns the tyre must effectively twist from top to bottom

Yep, though mostly at the bottom.

And one of my faves, Top Fuel drag cars. The rear tyres do an amazing job – When launching off the line, they act like a big spring, storing energy for later release to help accelerate the car. And with the low ~7.25 psi pressure they run, they squat down a lot as the g-force starts, thus helping decrease the effective diameter and so increasing the torque at the contact surface. They get off the line at about 4.5 G’s, then that picks up to about 6 G’s after a second or so as the tyre really starts to be able to bite into the track.

Then at high speed they increase in diameter to likewise increase the overall gearing to reach a higher top speed. They go from zero to 500 km/h in just under four seconds.

Crazy stuff, 0 – 500 too much for me. The lifetime of a drag tyre would short I reckon.

Further thought

Minimise the weight of the vehicle. Maybe the quality of the asphalt hadn’t changed but the weight of the average vehicle. Have lighter vehicles with better suspension?

wookiemeister said:

Crazy stuff, 0 – 500 too much for me. The lifetime of a drag tyre would short I reckon.

Top Fuel tyres last two runs.

Spiny Norman said:

They go from zero to 500 km/h in just under four seconds.

Long ago, a mate who flew Skyhawks off HMAS Melbourne told me that the catapult launch took him from 0kmh to about 300 kmh in just a fraction under 3 seconds.

Seems that top fueller take-offs are not dissimilar!

I was watching something about tyre quality

Tyres manufacturing dates. The older the tyre the harder it becomes.