Two Seat Cobra Trailer Tire Replacement

On Monday, May 10, 2021 at 8:23:04 AM UTC-7, AS wrote:
Trailers are designed with tandem axles because one axle can't carry the load of the trailer, not to provide greater stability. When turning while pulling a tandem the axles are not aligned with the center of rotation - they can't be because the axles are parallel. The tires want to go in a different direction than the rotation of the turn and must, to some degree, scrub to make the turn. This is why maneuvering them by hand is so difficult. The same thing is happening when being towed but the power of the tow vehicle forces the tires in the direction of the turn. This scrubbing action deteriorates stability, not enhances it.

Tom

Trailers are designed with tandem axles because one axle can't carry the load of the trailer, not to provide greater stability.
I call 'hog-wash' on this one! There are a few trailers by the same manufacturer with the same glider inside in the exactly the same configuration but they have a single axle with larger wheels. The load bearing capability is the the same in both cases. Going to a tandem axle enhances stability (tracking) and allows the whole trailer to sit lower since the wheels on the tandem axle are typically smaller. Lower CoG = more stability.
I completely agree with your point of them being a pain in the butt to man-handle them.

Uli
'AS'

The tire scrubbing that does occur during turning (no one seems to dispute that as it is obviously true) cannot "enhance" stability; the trailer is literally fighting being turned by the tow vehicle. If this were the case then adding even more axles would make the trailer even more stable. Trailers, or vehicles, with many axles (transporters) articulate the wheels for this reason.

Tom

On 5/16/21 11:14 AM, 2G wrote:
On Monday, May 10, 2021 at 8:23:04 AM UTC-7, AS wrote:
Snipperoo...

Trailers are designed with tandem axles because one axle can't
carry the load of the trailer, not to provide greater
stability.
I call 'hog-wash' on this one! There are a few trailers by the same
manufacturer with the same glider inside in the exactly the same
configuration but they have a single axle with larger wheels. The
load bearing capability is the the same in both cases. Going to a
tandem axle enhances stability (tracking) and allows the whole
trailer to sit lower since the wheels on the tandem axle are
typically smaller. Lower CoG = more stability. I completely agree
with your point of them being a pain in the butt to man-handle
them.

Uli 'AS'

The tire scrubbing that does occur during turning (no one seems to
dispute that as it is obviously true) cannot "enhance" stability; the
trailer is literally fighting being turned by the tow vehicle. If
this were the case then adding even more axles would make the
trailer even more stable. Trailers, or vehicles, with many axles
(transporters) articulate the wheels for this reason.


Well, hey - since this thread began with discussing a glider-trailer
towing topic, better into the thread-drift weeds than verge weeds, I
suppose...

I am not a professional trailer designer nor have I played one on
TV...but I've delivered manufacturing-componentry-parts to a dozen (or
so) of 'em in my engineering retirement. I'll bet my retirement slush
fund that multiple reasons exist for quantity-of-axles choices for a
given trailer design, trailer/axle carrying capacities *generally* being
near the top of the list.

As for trailer stability, it'd be difficult to get a more stable trailer
than one with infinite rolling-resistance drag. Or any other kind of
drag, for that matter. I am, of course, assuming that keeping the CG of
any towed trailer behind the towing vehicle while said vehicle is moving
forward, is desirable...

I'll further bet some of my retirement slush fund winnings from above,
that the somewhat-implicit assertion of the final sentence of the above
snippet, is "debatable" (as in, the sweeping claim made, is far from "an
absolute, given, fact") - with the desire for increased stability (or
its lack) *not* being at the top of a designer's list of rationales for
incorporating steerable trailer tires.

YMMV.

Bob W.

We just need an extra crew or autopilot to steer the trailer:

https://youtu.be/xa2ihMkzX3g

I think you've got the base wrong.
Stability is defined as a the resistance of a system to the influence of a disturbance.
If you are driving along with your trailer, a lateral wind gust will push the trailer to the side nd causing it to sway.
Having two axles, the scrubbing of the tires will damp the push to the side - that's the definition of increased stability.

Le dimanche 16 mai 2021 Ã* 19:14:22 UTC+2, 2G a écritÂ*:
On Monday, May 10, 2021 at 8:23:04 AM UTC-7, AS wrote:
Trailers are designed with tandem axles because one axle can't carry the load of the trailer, not to provide greater stability. When turning while pulling a tandem the axles are not aligned with the center of rotation - they can't be because the axles are parallel. The tires want to go in a different direction than the rotation of the turn and must, to some degree, scrub to make the turn. This is why maneuvering them by hand is so difficult.. The same thing is happening when being towed but the power of the tow vehicle forces the tires in the direction of the turn. This scrubbing action deteriorates stability, not enhances it.

Tom

Trailers are designed with tandem axles because one axle can't carry the load of the trailer, not to provide greater stability.
I call 'hog-wash' on this one! There are a few trailers by the same manufacturer with the same glider inside in the exactly the same configuration but they have a single axle with larger wheels. The load bearing capability is the the same in both cases. Going to a tandem axle enhances stability (tracking) and allows the whole trailer to sit lower since the wheels on the tandem axle are typically smaller. Lower CoG = more stability.
I completely agree with your point of them being a pain in the butt to man-handle them.

Uli
'AS'
The tire scrubbing that does occur during turning (no one seems to dispute that as it is obviously true) cannot "enhance" stability; the trailer is literally fighting being turned by the tow vehicle. If this were the case then adding even more axles would make the trailer even more stable. Trailers, or vehicles, with many axles (transporters) articulate the wheels for this reason.

Tom

On Monday, May 17, 2021 at 12:53:51 AM UTC-7, Tango Whisky wrote:
I think you've got the base wrong.
Stability is defined as a the resistance of a system to the influence of a disturbance.
If you are driving along with your trailer, a lateral wind gust will push the trailer to the side nd causing it to sway.
Having two axles, the scrubbing of the tires will damp the push to the side - that's the definition of increased stability.
Le dimanche 16 mai 2021 Ã* 19:14:22 UTC+2, 2G a écrit :
On Monday, May 10, 2021 at 8:23:04 AM UTC-7, AS wrote:
Trailers are designed with tandem axles because one axle can't carry the load of the trailer, not to provide greater stability. When turning while pulling a tandem the axles are not aligned with the center of rotation - they can't be because the axles are parallel. The tires want to go in a different direction than the rotation of the turn and must, to some degree, scrub to make the turn. This is why maneuvering them by hand is so difficult. The same thing is happening when being towed but the power of the tow vehicle forces the tires in the direction of the turn. This scrubbing action deteriorates stability, not enhances it.

Tom

Trailers are designed with tandem axles because one axle can't carry the load of the trailer, not to provide greater stability.
I call 'hog-wash' on this one! There are a few trailers by the same manufacturer with the same glider inside in the exactly the same configuration but they have a single axle with larger wheels. The load bearing capability is the the same in both cases. Going to a tandem axle enhances stability (tracking) and allows the whole trailer to sit lower since the wheels on the tandem axle are typically smaller. Lower CoG = more stability.
I completely agree with your point of them being a pain in the butt to man-handle them.

Uli
'AS'
The tire scrubbing that does occur during turning (no one seems to dispute that as it is obviously true) cannot "enhance" stability; the trailer is literally fighting being turned by the tow vehicle. If this were the case then adding even more axles would make the trailer even more stable. Trailers, or vehicles, with many axles (transporters) articulate the wheels for this reason.

Tom

Two tires does double the sidewall resistance to rolling. The surface area of a glider trailer (30' x 3') exposed to a side gust, however, is pretty small compared to my travel trailer (33' x 8'). I can tow my glider as fast as the speed limit allows (80 mph in places) w/o roll or yaw stability problems (single axle), but I will slow down to 55 or 60 if it gets gusty while towing the travel trailer. I do tow with large vehicles (F-250 Super Duty), not baby SUVs, which makes a difference.

Tom