Trailer Design - Resources?

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Vigilant1

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What if the elastomer rubber was removed from the "torsion axles", and a simple OTS shock absorber was put in between the trailing arm and the trailer frame? This would give you independent suspension (reduce trailer rock n' roll), longer travel (less impact damage) , and damping (less bounce).
You'd also need a coil spring around the shock absorber.
The setup might work well, but it would take tweaking (i.e. "iterative engineering") to figure out the right spring and shock absorber combo.
 

Vigilant1

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You may want to paint, especially the steel. Painting stuff like this often takes a backseat but is easier if planned in the building process.
I saw one site that recommended that folks buy a wax ring (used to seal a toilet to the toilet flange), warm it and the leaf springs up, and spread the wax liberally so it can get between the leaves to reduce/eliminate water (and road salt, if applicable) intrusion and subsequent rust. Sounds messy, but probably cheap and effective for a long time.
 

Vigilant1

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What if the elastomer rubber was removed from the "torsion axles", and a simple OTS shock absorber was put in between the trailing arm and the trailer frame? This would give you independent suspension (reduce trailer rock n' roll), longer travel (less impact damage) , and damping (less bounce).
Does anyone make something like that that's "bolt-on", that I can buy outright rather than fabricate?
I'm not aware of a bolt-on trailing arm like that. If you wanted shocks and coil springs (but no trailing arm), you could buy and adapt the used front end components from a (big) vehicle that uses MacPherson struts or a similar coilover design. It would be a job.
1631733912769.png

I'm not aware of many small trailers that use coil springs and shocks. The Tee-Nee boat trailer used them, but they were produced many decades ago, and I think most of the ones still on the road have converted to leaf springs.

Old Tee-Nee trailer:
1631734687774.png

There >are< bolt-on trailing arm designs that aren't leaf springs or torsion axles. The trailing arm compresses a rubber block during its travel. I don't know how damping is accomplished (just internal friction in the rubber + tire scrub?) and I don't know how well they hold up if they have a lot of weight on them constantly. My >guess< is that rubber/elastomer in compression like this sags less than the rubber in torsion axles, and that these rubber pucks are easier/cheaper to change out.
More here: https://www.etrailer.com/Trailer-Leaf-Spring-Suspension/Timbren/ASR2000S02.html?feed=npn&utm_source=bing&utm_medium=cpc&utm_campaign=Bing | Shop - Trailer Leaf Spring Suspension&utm_term=4577129471796911&utm_content=30 - 60

1631735778293.png
 

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fly2kads

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This is a really good thread. I like the practical insights and experience being shared here!

I have thought about using a boat trailer as the starting point for an aircraft hauler and storage, similar to the purpose that Topaz envisions. As someone who likes to study existing designs, I have wondered if these plans from Glen-L would be worth the modest investment, just to see the detail design of how a trailer can be constructed:
Boat Trailers-boatdesign
 

Topaz

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... There >are< bolt-on trailing arm designs that aren't leaf springs or torsion axles. The trailing arm compresses a rubber block during its travel. I don't know how damping is accomplished (just internal friction in the rubber + tire scrub?) and I don't know how well they hold up if they have a lot of weight on them constantly. My >guess< is that rubber/elastomer in compression like this sags less than the rubber in torsion axles, and that these rubber pucks are easier/cheaper to change out.
More here: https://www.etrailer.com/Trailer-Leaf-Spring-Suspension/Timbren/ASR2000S02.html?feed=npn&utm_source=bing&utm_medium=cpc&utm_campaign=Bing | Shop - Trailer Leaf Spring Suspension&utm_term=4577129471796911&utm_content=30 - 60

View attachment 115638
Another page clipped into the notebook! Thanks!

I'm leaning more and more towards a bolt-on solution like this, rather than scavenge a car suspension or such. Just don't want to "fiddle" with something, especially for a trailer. The more I can "bolt it together and go," the more I like it.
 

Vigilant1

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I'm leaning more and more towards a bolt-on solution like this, rather than scavenge a car suspension or such. Just don't want to "fiddle" with something, especially for a trailer. The more I can "bolt it together and go," the more I like it.
As you mentioned previously, make that pilgramage to the DMV and correspond with some Californians who have built their own trailer before getting too far down any particular DIY path. You may find that you need a used trailer or trailer hulk (and all that comes with it) just for the dataplate/VIN/transferrable title.
 

Topaz

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As you mentioned previously, make that pilgramage to the DMV and correspond with some Californians who have built their own trailer before getting too far down any particular DIY path. You may find that you need a used trailer or trailer hulk (and all that comes with it) just for the dataplate/VIN/transferrable title.
I looked at the CA DMV website section for "Specially Constructed Vehicles" and there doesn't seem to be any such restriction here. The usual ream of forms and fees, but nothing untoward. They mention the case of building a trailer from a kit, but I don't believe what I want qualifies for that.

Given that this is California, I'll double-check in person before I get started on anything, but so far the requirements don't see to be too onerous.
 

Hephaestus

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Look at the coilovers - fox or offshore - there's engineering sheets out there; you can dial in your dampening/spring rates/rebound etc really easily... Pretty sure there are some excel spreadsheets to work out the rates/weights/hole sizes you'll need. It's fairly inexpensive way to go. I mean we can get them for everything from scrappy to kids electric scooters now - with pretty much no gaps between sizes/bores/strokes/budget...
 

Victor Bravo

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Absolutely not being snarky at all, legitimate question: Did any of the glider trailers you ever owned have gas shocks?
No, they did not to my knowledge. I remember wishing there was some kind of damper to keep the things from jumping up and down constantly. I vowed that if I ever built one it would have a soft and we'll damped suspension.
 

Wolfen1176

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So DMV website should tell you all the legal stuff about trailers and I went there first. Also say you build a trailer in one state but want to tow into another the neighboring state may have different dimensions they consider legal.
The trailer weights, dimensions, brake requirements, etc are federal laws not state laws.
 

Vigilant1

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The trailer weights, dimensions, brake requirements, etc are federal laws not state laws.
Laws differ by state in some ways. For example, in some states 8' 6" width is allowed only on some designated roads, otherwise it is 8’ 0".
And, aside from what is legal to operate on a particular road, do states have discretion regarding what they allow in a vehicle that is registered in their state?
 

Topaz

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Thanks, that works!

However, we're getting into duplicates now. Karmarepair posted that same document in post #8, and I realize in looking through my OneNote notebook that I've gotten the Timbren "rubber block" axle-less suspension twice now, as well.

The trailer weights, dimensions, brake requirements, etc are federal laws not state laws.
Pretty sure that's for inter-state commerce; the big commercial tractor-trailer rigs. As Vigilant1 notes, for non-commercial trailers I believe that each state has its own rules for motor vehicles. There are certainly some federal rules as well but, as is overall, states have priority where federal law doesn't apply.
 

Dana

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I'm less worried about condensation than the brutal heat of the summer here. At the gliderport where I've flown most often, mid-day summer temps reach 110-115°F with some regularity. Even if the vents are a little spendy, having two should move a lot of air through the trailer and keep it from getting much above ambient.
I had four lovered vents, about 8"x10" each, in my trailer. Two at floor level on either side in the front, and two high on the rear doors. It never seemed to get excessively hot inside, granted this was New England and not Socal. The RV world has all kinds of vents, both active and passive.

Yes, the plan is to trailer the glider every day it's flown. If it's a particularly good season, I may spring for a tie-down at the gliderport for a few weeks, but the airplane will live in the trailer at the gliderport, too. Irrational or not, I don't want the craft of my hands out exposed to the dirt, dust, direct sunlight and, unfortunately, rare vandalism at the gliderport.
I kept my Kolb in the trailer, at the airport, during the summer flying season ($60/month), and at home during the winter. I would haul it to the airport on the occasional nice winter day, but it would get old pretty fast if I had to haul the trailer more than once a month or so. Plus, at the airport all I had to do was roll the plane inside, no need to strap it down as I had to do to take it on the road.

If the trailer is enclosed and sealed why do you need to keep it in an indoor storage unit???
 

aivian

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I don't have any design resources, but I've had the misfortune to deal with a variety of home built sailplane trailers and fortune to deal with a number of name brand ones. Regardless I rig and derig almost every time I fly (now from a "homebuilt" Jiran half-clamshell which is the best of the homebuilt's I've run across) so I have a fair list of things I've noticed.

First, a lot of suboptimal trailer characteristics can be made manageable if your ship is light enough. I flew a Russia AC-4 for a while which was in a tube trailer that required you to reach in and lift the wing dollies out of the trailer then hold the wing root suspended while removing them. This would have been extremely difficulty except that the wing roots were only ~60lb. My current Libelle trailer has a hinged between the tongue and axle to raise the front of the trailer instead of the rear ramp-jack. This makes getting the fuselage into exactly the right spot on the dolly difficult, but the ship is so light that I can just scoot the fuselage into the right place after the wings are off.

(as an aside, an aircraft detail that helps a lot -- make sure the main wheel protrudes slightly forward of the landing gear doors so that you can just roll the fuselage forward until it hits the ramp, back of the trailer, or dolly rather than having to gingerly approach to avoid smashing the gear doors)

On to some trailer details...

Tube or clamshell:
Tubes are easy, but almost every one I've worked with is a bit difficult to get the wing roots back onto the dolly. The dolly is inside the trailer and you need to get the wing root into there. The fuselage is in the way on the inside and the side of the tube is in the way on the outside so you end up reaching in with an awkward cantilevered motion. The exception I've seen is my dad's Libelle trailer (not quite actually a tube, but it is for this purpose), where the rear door hinges at the bottom and folds out with a little stand that holds it at trailer floor height, then the dollies can roll out onto the door so you can easily get at them from the outside. Clamshells neatly solve this problem because you can get at the outside edge of the dollies. My current trailer is a half-clamshell (top hinged just aft of the axle), this works about as well as a full clamshell for rigging but is more difficult to make waterproof

Fuselage Dolly:
By far the easiest to deal with is the German style with the pull-out ramp and a jack. You roll the fuselage up until the wheel hits the jack (the main wheel does extend slightly forward of the gear doors right???), then jack up the ramp and everything is in exactly the right place. Other styles I've worked with:

- Dollies that stay in the trailer (my current one, requires at least a half-clamshell to keep things from getting too crowded) or are on non-adjustable ramps work but usually require the fuselage to be repositioned after the wings are off.
- Contraptions which ride down a ramp but grab the lift pins rather than having a dolly. This worked on the russia because it didn't weigh anything so when you ended up having to hold up the fuselage because you screwed something up it wasn't too bad.
- Contraptions which slide on an overhead track and grab the lift pins. *shudder* my first libelle trailer had this. It took two people to get the fuselage back in and you lived in constant fear of dropping the contraption through the canopy.

Wing dollies:
It is tempting to simplify the tracks and make them not-tightly-constrained as they roll back-and-forth. My first libelle trailer just had little wooden 1"x1" strips to vaguely guide the dollies which were on lawnmower wheels. They could jump the strips, this was very aggravating. Another trailer I used had PVC pipes for guides which worked better but was prone to friction.

As for the wing-dolly interface. A screw-on clamp works but is a bit of a pain. Much better are drop-on interfaces where the wing is not required to stay rigidly clamped to the dolly. The Cobra folks have this figured out by using a plate fixed to the front of the trailer which you put the spar underneath so that the wing can't bounce up and out. Note that regardless of how you do this, a large diameter spar pin helps a lot. The Libelle spar pin is about a pinky-finger diameter, it is difficult to sight through it and line up the dolly, especially on the "fork" wing side. The large schempp and schleicher pins are easier to sight through and also allow a rounded delrin pin on the dolly so that you only have to get close.

When it comes to keeping the dolly from sliding fore-and-aft during trailering. A pin through the dolly works, but requires an awkward reach in through the front door. Modern german gliders seem to have some kind of chock at the front, and then constrain the wing tip from moving aft. This is much easier.

Vents:
I have a solar vent, it seems to work. I don't stress about it -- I live in the desert so moisture isn't a huge concern, and the libelle manual specifically requests that you let your ship sit in the trailer on a hot day to help the post-cure on the epoxy.

Forward access:
A door in the front of the trailer is great (and mandatory if you pin the dollies in). If you want to store anything in there though it needs to be tied down or else there needs to be some kind of bulkhead to keep it from wandering aft during trailering. Also note that front doors have a long and glorious history of flying open and departing at highway speeds.

Tail storage:
A clamshell easily accomodates a fixture on the trailer top for the tail. Otherwise you are looking at some kind of fixture that either installs between the rear fuselage and wing and can be slid out before rigging, an awkward reach through the front door to a fixture in the front, or else a fixture that attaches to the top of the rear fuselage. The top of the rear fuselage is weird and I've only seen it on one trailer but was the most satisfactory tail holder for a tube trailer I've seen.

Suspension:
I don't have much comment here. I have personally gotten a torsion axle replaced on a trailer which had the elastomer wear out. This was as easy as measuring it, writing a reasonable size check, and taking it to the local welding shop. I have leaf springs on my current trailer but will replace with a torsion axles sometime, the replacement is just a lot easier to figure out.

Zooming back out. There are a bunch of little details that make trailers work or not. The Germans have this pretty thoroughly figured out, given the option between putting a 15 m glider away in a Cobra trailer or jockeying it into a hangar, I think it is easier to put it in the trailer. I feel similarly about my trailer provided I have someone willing to lift a wing for a few minutes. All this to say, I really recommend spending some time with a Komet or Cobra. If possible help someone rig from one a dozen or so times to see how it all works together.

Finally, I hope there is enough content up there to indulge a slight divergence from what you'd originally asked which is to suggest: if it is physically and financially feasible, just buy a Cobra or Komet (or a Komet kit Anschau Technik GmbH - Komet ECO-Smart Kit). Last time I saw a price list for Komet's they were not completely ridiculous, especially considering the effort involved in designing and building a trailer of equivalent quality.
 
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