Gentle-people of RAS Prime,

I have been thinking for years about trying to help glider trailer jockeys to make sure that their trailer doesn't become a un-guided missile while traveling down the highways and byways.

This was to be an article in Soaring magazine but turns out to be more of a visual, rather than textual, discussion area. I suppose it could be a series of articles. But I digress.

So, as I like to do, I put the thoughts running around in my head, and the attendant images, into a presentation.

After some others reviewed my draft version it is now in pretty good shape. I would like have a few of you to review what I have written and do a sanity check. Does it make any sense? Is it logical? Is it missing things? Some stuff downright wrong?

Please let me know. You can download a copy at; aviation.derosaweb.net/presentations/documents/Trailer_Chains.pdf

Thanks, John OHM

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Slide 13 taut

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Quick read: looks great!

JJ

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On Sunday, August 13, 2023 at 12:58:09 PM UTC-4, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:

Gentle-people of RAS Prime,

I have been thinking for years about trying to help glider trailer jockeys to make sure that their trailer doesn't become a un-guided missile while traveling down the highways and byways.

This was to be an article in Soaring magazine but turns out to be more of a visual, rather than textual, discussion area. I suppose it could be a series of articles. But I digress.

So, as I like to do, I put the thoughts running around in my head, and the attendant images, into a presentation.

After some others reviewed my draft version it is now in pretty good shape. I would like have a few of you to review what I have written and do a sanity check. Does it make any sense? Is it logical? Is it missing things? Some stuff downright wrong?

Please let me know. You can download a copy at; aviation.derosaweb.net/presentations/documents/Trailer_Chains.pdf

Thanks, John OHM

slide 12: should be 50.8 mm not 0.8 mm

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On Sunday, August 13, 2023 at 4:37:31 PM UTC-7, Dan Goldman wrote:

On Sunday, August 13, 2023 at 12:58:09 PM UTC-4, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:

Gentle-people of RAS Prime,

I have been thinking for years about trying to help glider trailer jockeys to make sure that their trailer doesn't become a un-guided missile while traveling down the highways and byways.

This was to be an article in Soaring magazine but turns out to be more of a visual, rather than textual, discussion area. I suppose it could be a series of articles. But I digress.

So, as I like to do, I put the thoughts running around in my head, and the attendant images, into a presentation.

After some others reviewed my draft version it is now in pretty good shape. I would like have a few of you to review what I have written and do a sanity check. Does it make any sense? Is it logical? Is it missing things? Some stuff downright wrong?

Please let me know. You can download a copy at; aviation.derosaweb.net/presentations/documents/Trailer_Chains.pdf

Thanks, John OHM

slide 12: should be 50.8 mm not 0.8 mm

The most glaring shortcoming is that there is no mention of the types of hitches or their ratings. Maybe you think that any car and/or hitch can tow a glider trailer, but this is not the case. Any side forces on the trailer have to be countered by the
tow vehicle's front tires, over and above the normal side forces encountered during turns. This will, no doubt, trigger a spirited discussion of what vehicles are suited for towing glider trailers. I believe that just going by the tow rating of the
vehicle is bordering on dangerous as glider trailers are much longer than your typical trailer. Here is a compilation of similar accidents:
https://www.youtube.com/watch?v=APKjtumuNs0

Tom 2G

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Tom 2G - Yep, I totally agree. But I consciously decided that it would be impossible to try to cover the topics of which are the "best" cars/trucks/SUVs, hitches, etc. I spell that out in slide #10. FAR too many variables for this (electrical)
engineer.

- John (OHM)

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On Sunday, August 13, 2023 at 6:34:57 PM UTC-7, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:

Tom 2G - Yep, I totally agree. But I consciously decided that it would be impossible to try to cover the topics of which are the "best" cars/trucks/SUVs, hitches, etc. I spell that out in slide #10. FAR too many variables for this (electrical) engineer.

- John (OHM)

I wish we had an easy way for the driver to determine the maximum "safe" towing speed of his particular vehicle/trailer combination. The current technique seems to be ...

1) drive at steady speed, jerk the wheel, and then wait for oscillations to die out
2) Repeat at a higher speed until you half-frighten yourself.
3) Vow to never go within 5 mph of that speed again

Sometimes this is done deliberately, sometimes inadvertently. Maybe we can do something like the Perlan folks do: each wing has pair of rotating weights that can be driven over range of speeds to excite the wings. Deflections and frequencies are
monitored and recorded, then analyzed after the flight to discover resonances. It's a lot easier, quicker, and safer than flying the glider and jerking on the controls. Let's call it the "exciter".

A trailer version could be a single motor rotating weights on, say, a 16" square board that would be mounted on the floor of the trailer over the axle. The data logger would also be mounted on the board, and the whole unit turned on and off by a remote
switch in the vehicle. To test, the driver drives straight (no wheel jerking!) at a steady speed, turns the exciter on long enough to get the data, shuts it off, goes to the next speed, and so on.

After the data collection, the USB from the logger is plugged into a computer to crunch the data, and produce a chart of speeds with an estimated stability and safety. The driver now has something besides guesses to help him tow safely, and if he thinks
the "safe" speed is too low, he can make changes to his tow vehicle and trailer, test it, and repeat until he's happy.

Many years ago, Nelson Funston and I talked about ways to this. I did some testing using a dash cam mounted on top of the trailer tail fin, looking forward. Besides the dashcam's camera to record the motion of the of the tow car and trailer, it had (as
do most of them) accelerometers in it that can record the oscillations, and a GPS to record speed and direction. We didn't get very far with it, due in part to slow recording rates of the dashcam, and his computer models being in written an elderly
version of Fortran, making it hard to convert to new programming languages.

So, it there anyone out there that has the smarts to analyze trailer motion? Perhaps a grad student working on (or looking for) a thesis project? I don't think the exciter would be difficult to design and fabricate.

Eric

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One word of warning is to make sure Cobra surge brake trailer chains never drag on the ground when the surge brake is compressed. The resulting sparks can be a source of roadside fires. Loosely raise the center of the chain with something that will break
(zip tie?) if the hitch fails or modify the chain/trailer secure location. Perhaps also add a word of caution on purchasing pre-packaged trailer chain sets. Their length is usually designed for a normal V shaped trailer tongue and are probably too short for a straight glider trailer tongue length.
Craig

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On Monday, August 14, 2023 at 10:01:23 AM UTC-4, Craig Reinholt wrote:

One word of warning is to make sure Cobra surge brake trailer chains never drag on the ground when the surge brake is compressed. The resulting sparks can be a source of roadside fires. Loosely raise the center of the chain with something that will

break (zip tie?) if the hitch fails or modify the chain/trailer secure location.

Perhaps also add a word of caution on purchasing pre-packaged trailer chain sets. Their length is usually designed for a normal V shaped trailer tongue and are probably too short for a straight glider trailer tongue length.
Craig

The chains on my dual-axle trailer are running along the V-shaped trailer tow bar and attached to the body of the trailer. I have seen way too many chains being attached to the tow bar itself.
I tie up the loose chain with a set of small diameter bungee-cords. They are more flexible than a zip-tie and cheap enough to replace, once they loose their 'bungeeness'

Uli
'AS'

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Perhaps also add a word of caution on purchasing pre-packaged trailer chain sets. Their length is usually designed for a normal V shaped trailer tongue and are probably too short for a straight glider trailer tongue length.
Craig

I agree on the subject of making sure safety chains the correct length and ensuring they do not bind up when turning sharply, nor drag on the ground. Also, they should attach to the trailer body itself, and not to the tongue. Cobra generally has them
bolted at the front edge of the trailer body right next to the tongue where it exits from the box. I prefer to fabricate a dedicated steel plate that is held by the front tongue mount bolts and has a couple of "eyes" or welded loops for the chains to
connect with threaded carabiners. This makes it easy to adjust the chain length for different receivers and tow vehicle attach points.

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On Monday, August 14, 2023 at 9:55:20 AM UTC-5, Mark628CA wrote:

Perhaps also add a word of caution on purchasing pre-packaged trailer chain sets. Their length is usually designed for a normal V shaped trailer tongue and are probably too short for a straight glider trailer tongue length.
Craig

I agree on the subject of making sure safety chains the correct length and ensuring they do not bind up when turning sharply, nor drag on the ground. Also, they should attach to the trailer body itself, and not to the tongue. Cobra generally has them

bolted at the front edge of the trailer body right next to the tongue where it exits from the box. I prefer to fabricate a dedicated steel plate that is held by the front tongue mount bolts and has a couple of "eyes" or welded loops for the chains to
connect with threaded carabiners. This makes it easy to adjust the chain length for different receivers and tow vehicle attach points.

Mark,

I agree that attaching the chain to the body of the trailer is the better approach. On the square tongue Cobra trailers the connection point is pretty darn strong with a thick U strap inside. If you look at slide #16 I talk about my opinion to attach
the chain to the trailer (frame and/or tongue) in multiple places. The lower-left picture is an example of a Cobra trailer attaching the chain in three places (one on the frame and two on the tongue). More is better?

- John (OHM)

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On Monday, August 14, 2023 at 10:03:37 AM UTC-5, AS wrote:

On Monday, August 14, 2023 at 10:01:23 AM UTC-4, Craig Reinholt wrote:

One word of warning is to make sure Cobra surge brake trailer chains never drag on the ground when the surge brake is compressed. The resulting sparks can be a source of roadside fires. Loosely raise the center of the chain with something that will

break (zip tie?) if the hitch fails or modify the chain/trailer secure location.

Perhaps also add a word of caution on purchasing pre-packaged trailer chain sets. Their length is usually designed for a normal V shaped trailer tongue and are probably too short for a straight glider trailer tongue length.
Craig

The chains on my dual-axle trailer are running along the V-shaped trailer tow bar and attached to the body of the trailer. I have seen way too many chains being attached to the tow bar itself.
I tie up the loose chain with a set of small diameter bungee-cords. They are more flexible than a zip-tie and cheap enough to replace, once they loose their 'bungeeness'

Uli
'AS'

Uli,

Two comments;

When you say "tow bar" I assume you are referring to the "tongue".

As to using a bungee to tie up loose chain. I assume this is to effectively "shorten" the chain. I cover shortening chains on slides #19-#21. Slide #21 basically says that your bungee method is a no-no and the reason why.

Let me know what you think.

- John (OHM)

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Two comments;

When you say "tow bar" I assume you are referring to the "tongue".

Correct - the thing between the towing vehicle and the trailer. ;-)

As to using a bungee to tie up loose chain. I assume this is to effectively "shorten" the chain. I cover shortening chains on slides #19-#21. Slide #21 basically says that your bungee method is a no-no and the reason why.

No, not to shorten the chain but to keep the necessary slack chain off the road. My tow hitch is pretty low and the slack chain required to make steep turns would hit the road surface when going straight. I use the bungee from one chain belly over the
tongue to the other chain belly. That way, the slack is always up but can stretch out unimpeded, when required.

I looked at the links you provided and I have to disagree with the method of wrapping the chain through the hole provided on the vehicle's structure as shown under 'Length Shortening Methods'. In this case, the chain link that is going through the hole
is side-loaded when the chain is pulled on. Chains are not supposed to be loaded like this (only in straight pull) and it severely reduces their capacity. You can look it up in the Rigging Handbook, page 103. (and yes, I hold a Riggers Certificate ;-) )
In our application, it may not matter but it is a no-no in heavy lift operations.

The chain shortener with the two forked ends is a good way to shorten the chain without cutting it.
I use drop-forged hooks with a spring-loaded gate and a rating that is higher than the chain itself. I don't trust these bent round bar hooks. They look flimsy to me.

Uli
'AS'

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I agree that attaching the chain to the body of the trailer is the better approach. On the square tongue Cobra trailers the connection point is pretty darn strong with a thick U strap inside.

I agree that the attachment point is strong enough, I just don't like the method of running the bolt through the chain and using washers and the nut to capture the link. The bolt threads are susceptible to deformation by the chain, and there is no easy
way to adjust the length except by unbolting it.

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On 8/13/2023 11:58 AM, John DeRosa OHM Ω http://aviation.derosaweb.net
wrote:

Gentle-people of RAS Prime,

I have been thinking for years about trying to help glider trailer jockeys to make sure that their trailer doesn't become a un-guided missile while traveling down the highways and byways.

This was to be an article in Soaring magazine but turns out to be more of a visual, rather than textual, discussion area. I suppose it could be a series of articles. But I digress.

So, as I like to do, I put the thoughts running around in my head, and the attendant images, into a presentation.

After some others reviewed my draft version it is now in pretty good shape. I would like have a few of you to review what I have written and do a sanity check. Does it make any sense? Is it logical? Is it missing things? Some stuff downright wrong?

Please let me know. You can download a copy at; aviation.derosaweb.net/presentations/documents/Trailer_Chains.pdf

Thanks, John OHM

John,
I do not see a link to the article. Could you post it please? Thank-you.

--
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On 8/14/2023 2:24 PM, JC wrote:

On 8/13/2023 11:58 AM, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:

Gentle-people of RAS Prime,

I have been thinking for years about trying to help glider trailer
jockeys to make sure that their trailer doesn't become a un-guided
missile while traveling down the highways and byways.

This was to be an article in Soaring magazine but turns out to be more
of a visual, rather than textual, discussion area.  I suppose it could
be a series of articles.  But I digress.

So, as I like to do, I put the thoughts running around in my head, and
the attendant images, into a presentation.

After some others reviewed my draft version it is now in pretty good
shape.  I would like have a few of you to review what I have written
and do a sanity check.  Does it make any sense?  Is it logical?  Is it
missing things?  Some stuff downright wrong?

Please let me know.  You can download a copy at;
aviation.derosaweb.net/presentations/documents/Trailer_Chains.pdf

Thanks, John OHM

John,
I do not see a link to the article.  Could you post it please? Thank-you.

My browser did not go far enough down on the page to find the link, I
found it now. Sorry for the confusion.

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