Pusher-Trailer: A Bicycle-Frame Solution

[Kingfish]

Saturday June 18th

There are two Status lists that I am keeping; be sure to check out the Going to California thread to see status of the rest of my bike.

I have been slammed every day, and it’s been like a blur.

Bike Frame to Machinist: Delivered the frame to shop. Initially I thought of strapping it to my back, but this arrangement worked out well. It’s tied down with an inner-tube onto the rear rack; didn’t budge a whisker over the 10+ mile journey.

Custom Parts: Acting as a purchasing agent, I drew up the layouts that maximize stock material, contacted three suppliers sourcing materials, and finally placing a large order with McMaster-Carr on Thursday with the material arriving about 1:30 PM by FedEx yesterday; less than 24 hours.

Marine Plywood: Tracking says it will arrive on Tuesday.

Battery Boxes: The Sears Portable Tool Boxes arrived yesterday. I worked up a few battery configurations; there is plenty of room and not much to worry about. It just needs a little bit of hard foam and bolting down.

Battery Balancing: The 6-to-1 Balancing cables arrived I think on Wednesday and I cracked open the big box of LiPos from HK. Hooked up the Battery Medic and tried balancing: Boy is that device wimpy. I had better luck hooking up the Balancing cables. Out of the entire lot of HK batteries only one cell was out 0.1V while all the rest were within 0.03-0.05V. I counted myself lucky. Also strange is that the new LiPos are smaller than what I had purchased last year; they are skinnier! The weight is the same, they are just trimmer. No complaints.

Fenders: Bought the Electra Plastic Balloon Townie Fender Set, color – black. I’ll use that to construct the rear fender on the trailer.

Faring: Stopped at Tap Plastics and picked up a 2x4 sheet of White HDPE and a sheet of Black.

Power Cabling: Stopped at Vetco and snagged 8-AWG zip cord, heat shrink tubing and black zip ties.

Speedict: Received email this morning confirming the latest model shipping out from Hong Kong; should take 5-10 working days to get here. Hopefully it will arrive before I have to leave. This version has the fix which displays up to 100V, although I am unsure what other mods are applied under the hood.

Rear Hub: The Kris Holm 24” MtB rim & 24”x2.5” & Maxxis Hookworm wheel is now finished. Looks nice sitting next to my front wheel which I hope to mount Monday evening.

In all the trailer is coming together; the Machinist is busting his team to crank my stuff out. There will not be time to paint or plate the parts; I’m not worried about Stainless or Aluminum, however the CrMo steel will be hit with a dash of hi-temp black paint and baked dry in the oven. Other parts on my bike treated in this method are holding up well enough.

Speaking of paint I think I’ll hit the Lyen controllers with Black paint too; hide the glitter from potentially pesky magpies with evil ideas. :wink:

So much to do, so little time. Nine days and counting.
~KF

 

[Kingfish]

Thursday June 23rd

• Ordered various fasteners from McMaster-Carr; it was cheaper to buy in bulk rather than go to Home Despot and scrounge through the limited selection. These were delivered to the Machinist for final assembly.
• Purchased a squad of Anderson Power Pole connectors for the battery bus and the phase wires.
• Developed several battery layouts for the Battery Box. Ultimately I will stack the bricks on their wide sides in rows of 8 x 3 deep. The last row will have 9, so a couple will be turned on edge to fit.
• The Batt-box Cable Harness is coming along; tedious work. Wore out my soldering tip though Radio Shack carries my brand and it was quick to correct and keep going.
• The Marine Plywood arrived; it’s 4mm thick and slightly more flexible than I would like, though I think that if I put a coat of epoxy sealer on that it might stiffen up.
• The Machinist has finished cutting my custom parts – a total of 33 if you count all the work in the last 6 weeks.
• Parts went to Plating yesterday and I picked them up this evening; they look nice!
• Tomorrow we’ll begin putting the trailer together up to the point where I can bring it home and finish it up.

See Going to California for non-trailer status.

Gettin' there, KF

 

[Kingfish]

Friday June 24th
4 days to go...

Assembled the basic framework today at the Machinist. He was kind enough to open his shop up to me for small parts and finishing work; the details that can only be realized when parts are in hand. We assembled it up to the point where I could safely bring it home for more work. The platform section is very sturdy; I stood on the strut passing through the Bottom Bracket and bounced a bit; there's no flex there. However there is a little wobble if one were to jitter the handlebars agressively; not much chance of that happening in real life but good to know the mechanical aspects however obtained. The Machinist and the Welder discussed some options and I may add in another trust at the Hitch/Headset-Steerer interface to stiffen up the linkage.

The ride back was pretty smooth; you can tell it's there but it doesn't nag. Mainly I feel the slight drag of the rear hub motor. There is some tiny wobble, but nothing like I experienced yesterday when I had the Booster Pack mounted on the rear rack. The hitch breaks down in about 2 minutes - it worked exactly how I had planned it. In all, I am glad I went ahead and plated the parts; it is defintely eye-candy and catching attention all the way back to my abode. 8)

The last shipment arrived today; another 12 batteries. It will be a busy weekend finishing up the trailer and making it look all spiffy. But for now...

It's Miller-Time, er um - make that an authentic Northern German Pilsner! KF

 

[jonathanm]

wow....great job!

 

[Kingfish]

The only work I managed to get to on this since bringing it home was to inspect the slow leak in the tire. Turns out that the Kris Holm plastic rim liner is insufficient to prevent the tubing from being cut. I resolved to fix the problem by adding a layer of Stop Flats 2, then wrapped another plastic liner over the top. I am awaiting a source for tire liner locally before re-inflating. If time allows I’d like to pull the hub cover off and upgrade the phase wires to 12-AWG. My trip is now delayed about two days, but I’d rather be ready than not.

~KF

 

[llile]

I've built trailers, never electrified, but here is a key engineering point on trailers. The squirrelliness some folks mentioned is a symptom of lack of rigidity int he system. When I built the first one-wheel trailer, I loaded it up with camping gear for a shakedown cruise, and it scared the bejeebers out of me going down a big hill. Wobbling back and forth out of control. I reinforced some key parts of it with some triangulation and some more rigid steel and the wobbling stopped. Grab the trailer in your hands and try to bend it at various weak points. Can you make it deflect, even a tiny amount? Say by twisting the parts that connect to the bike frame? That deflection can add up and feedback into a major fishtail under heavy loads.

I had the same problem on an old 1952 pickup with a loosey-goosey front end - load it too heavy and it would fishtail out of control if you went too fast downhill. I have also heard of people pulling overloaded trailers in pickup trucks having the same scary problem.

 

[Kingfish]

The wobble only appears when the trailer is mounted to the ebike, and even then it is a tiny shimmy. This occurs at the hitch-steerer interface. A small cross-brace should fix the problem however my machinist was unable to get to me this week due to the holiday. I might try something else to lock down the wobble; again it is very subtle.

I'll know more about the problem tomorrow when I begin putting a load on it.

I also bought a sway-dampening shock which I'll mount if it begins to squirrel-about

Best, KF

 

[Kingfish]

Brief Update:

• Yesterday I programmed the secondary controller which drives the trailer hub. It is not yet calibrated with the CA though.
• The night before I united the Throttle (SP), Cruise (CR), 3-Way (X1 & X2), and Ebrake (-EBS) with the primary controller,
• Enabled Regen (BK shorted to GRN),
• United VCC-L with Primary controller,
• However +12V and +5V are not shared.
• Both primary and secondary controllers have the R12 mod applied, and are programmed with a Voltage Limt of 32.0 and EMSLim at 60, which equates to New LVC at 50.528V and
• New HVC at 94.74V. The feeling is that on a 15S battery configuration the voltage drops rather quickly below 52V and there is not a lot to gain by setting the threshold lower except for the chance to bloat the batteries. The HVC limit is below the 100V limit of the MOSFETs.
• Replaced the two large capacitors with higher capacitance and lower ESR-rated/higher quality units on both controllers.
• Smoke test of united controls did not provide smoke – which is good.
• On yesterday's maiden voyage the Throttle and 3-Way worked perfectly. However Ebrake/Regen did not.

Overall - good news, though resolved to double-check circuit board and wiring.

The plan for today is to get the trailer to the machinist for one hitch mod to reinforce the interface and reduce the very slight wobble.

Work in progress, KF

 

[Kingfish]

Ebrake & Regen problem

Ran some tests this AM.

• With both wheels suspended, Throttle works on both hubs.
• Engaged the Ebrake: The front hub brakes whilst performing Regen, however the rear hub throttle is only cut-off and without Regen.
• Presumed I was in error when setting Regen on the PCB, therefore I extracted the unit and performed a continuity test of BK to GND; it passes.
• Reapplied the connection of BK to GND and tested continuity from BK to the Negative Battery connector; it passes.
• Reassembled the unit and tested: Throttle works. Applied Ebrake and Throttle is cut-out but there is no Regen.

I’m confused. Why would this not work?

ADDENDUM:
Noted yesterday that variable regen through the throttle was not working. I went into the programming application and set the SlipChargeMode to 0: UP 15 Mark (throttle regen) but this had no effect upon the motor.

Also, I discovered that the 3-Way Speed is not working properly; I definitely get 55% (Speed 2) but the freewheel speed is a little low so I think that the 90% (X1/Speed 1) speed is working, but not the 120% (X2/Speed 3).

I’ll reprogram the Primary controller to see if I can get the Throttle-Regen to work since eBraking-Regen does work.

ADDENDUM 2:
Well setting the SlipChargeMode to equal 0: UP 15 Mark produced another odd anomaly in the Primary controller: Ebrake works to cut out throttle, however it I get on the throttle then back off – the throttle now acts like a brake, so of how some big tractors work; power on or brake. The Secondary controller doesn’t behave like this at all. Weird. I’ll post this on the 12 x 4110 MOSFET Extreme Modder Controller LYEN Edition thread.


~KF

 

[Kingfish]

Wednesday July 6th

Blocked by lack of Regen on the Rear hub Motor. If the issue cannot be resolved then I have two alternatives:

• Hack my original tried-and-true 6FET into a Secondary. I R E A L L Y do not want to do that because I can no longer reprogram the device; many moons ago I was trying to remove the programming connector on the board and ended up tearing the pads off and it’s a bloody mess. This controller can only be used as a Primary as it's stuck at 120%. My plan was to carry it with me on my road trip as an emergency Primary backup.
• Provision an older 12FET unit that I bought from Dennis (another dealer) and slave it out. This unit has been partly modified for massive current with serious phase trace upgrade and 10AWG silver-plated Battery and phase wires; very ghetto At this point, I’m not going anywhere without Regen on that rear wheel; it’s a hard fixed must-have requirement because there is no other method to slow the trailer down.
• ADDENDUM: I just realized that I have a third option... I also have a Lyen 6FET Mini-Monster (4110) that is completely unmodified and left over from last year's trek when I was trying to do a 2WD ebike. That's likely the best option of the three because it's not going to run that hard (18A likely).

I'll be damned though if I can figure out what the issue is.

In other news, I began to put the deck together on the customized frame. It was getting late so I’ll save the power-tooling for the morning, though it looks like I could have something cobbled together by lunchtime. I want to finish it so I can put a load on the wheel so it won’t jump around.

Most other status relates to the trip in general and is covered on that thread.
~KF

 

[Kingfish]

Lyen 6FET Mini-Monster Test

Prepped Controller for temporary testing. Noted that the R1 resistor is 659 ohm; ideal would be 488 ohm for my 63V system. I do not yet know if this shall pose a problem on lower voltages; might need to dash off to radio Shack.

With Mini-Monster acting as a Primary controller to the Rear Hub:

• Throttle passes.
• Noted artifact that holding the Throttle for one second causes it to engage Cruise Control. Also noted that the single white wire with connector enables or disables the CR pin, so that is good. I have the dashboard setup to hold CR to GND with a momentary switch. Cruise Control passes.
• Tested 3-Way: N/C defaults to slow Speed 2; good. Shorted Red (X1) to GND and received the medium speed; good. Shorted Green (X3) and X1 to GND (the dashboard does this) and noted no change. Therefore I just shorted Green (X3) to GND only and – received the High Speed; 3-Way passes. Mental note to R&R dashboard control.
• Ebrake test: Left the High Speed engaged, and with a microswitch shorted –EBS to GND. Ebrake kills Throttle but does not engage Regen. Ebrake passes. Regen fails.
• Regen: Double-checked that BK was shorted to GND; continuity test confirms this is so. Why is this not working? Out of a lark, I disconnected BK from GND; result was no change.
• Note: The R1 and related voltage regulator are hot enough to fry my finger!

Conclusion: Resolved potential issue with 3-WAY and that is good. However Regen still does not work with this specific controller. The 6FET was flashes exactly the same as the Primary with exception to down-rated Battery and Phase Current (18A/45A) and that it is an EB206 board.

Not giving up:
I’m like a dog with a bone… Decided after reviewing the Configuration that I need to try one other test. I had the EBS Limit set to 60V, however I also have not done the R12 mod – so I changed it to 75V and retested. BK was disconnected and Ebrake had no change. Reconnected BK to GND and guess what? I’ve got Regen!

OK – so how does this affect my Secondary controller which has the R12 mod? Why does the Primary work with the EXACT same configuration? Off to review…
Feeling better, KF

 

[Kingfish]

Checked the R12 mod on the Secondary controller and it was a cold-solder joint. Made the repair and now Regen works!

Applying a fix to the 3-Way dashboard control, then moving back to the trailer decking. Machinist just called and he says I have to make my mods with him TODAY cos he's going on vaykay and "won't be available" as he puts it.

ADDENDUM: 3-Way from the dashboard control now works; top-end freewheel spun at 54.5 mph; we are good to go!

Going for it! KF

 

[Kingfish]

Brief Status:

Loaded up the trailer with a sacrificial deadweight using four frozen gallon jugs of water; figure about 30% of the expected weight capacity. Put them into my yellow Ortleib bags, tied it down, then headed out for the Machinist this afternoon. It was a FLAT-FREE experience! Actually it was a lot more than that:

• Imagine 3-WAY Speed control; I have it on the default which is 52%. It is enough to keep me at 21 mph with light pedaling – feels like a bike, moves like a bike, plenty safe for potential problem towns. The acceleration is awesome though short-lived.
• Moving out of the center of town I flicked the 3-WAY to the middle setting at 85%; there’s more power here than required; major power burst and acceleration for far longer. This is plenty fast for urban traffic at 31 mph, and climbs hills quite respectively without being a banshee.
• The rear wheel skipped less and dug in more; however corning could still be problematicv if powering on aggressively which in turn causes the rear to skip and bounce. At no time did the tail wag the dog; the front pulls harder and leads the bike forward.
• Regen-Braking is hard and jarring, and at one point the rear wheel squawked from hard regen. Unfortunately I have yet to figure out if these controllers can do variable regen like my old one. I may consider having the rear regen hard and the front regen a little softer. One idea that I recently read about is Shorting BK to GND when the Ebrake goes to GND so that we could coast farther as the two motors do produce quite a bit of drag.

Mounted the custom cross-brace to the lower hitch. The change was very subtle, and mainly bracketed to constraining axial and torsional moments about the hitch itself. There are several areas where the bike and trailer wobble: The trailer has an axial (twisting along the length) wobble. The bike has a side-to-side wobble introduced by the suspension. Lastly, the big fatty Hookworms on the Mavic rims deflect from side-to-side as well; a good strong sidewall would resist that motion.

Trailering required a little skill and attention; you know it’s there for good or bad. Definitely a kick in the butt to drive! My plan is to wrap it up tomorrow. It’s time to git on down the road.
Jonesin’ for wide open country. KF

 

[jonathanm]

Good skills with finding that dry joint, great you got it working....This has been a very exciting trip so far and you haven't even left yet!

 

[Kingfish]

Prelaunch
I was asked to post pictures on the Going to California thread, but they really need to go here.

These are “prelaunch” pictures – sort of unofficial release. I have the trailer finished up to a point where I plan to head out at first light tomorrow more or less. I am not particularly happy with the faring but time was short and I am already 2 weeks late for my holiday. There were issues in the past week that were just steal-your-life black holes and so tedious that is wasn’t worth reporting. I tried five times to cover the faring; Start a design, meh – try something else. It nearly didn’t get done. This is not my best sewing job either. It is not light; the vinyl weighs it down whereas the HDPE adds rigidity though is not very convenient for creating blends or 3D corners. Anyway – enough of my carping; the trailer is functional and that’s why it was made.

Exterior/Body

Top view from the back of the bike. I tried to stay with the colors black, white, and silver.

Side view with sort of a boat-motif. This popped into my head a couple of days ago as I was walking to the store. The original design was to have a waterproof zipper down the centerline – but I figured with my sewing skill and that cumbersome industrial sewing machine – I’d better not. Thus the boaty-tie-down method. Works well to create tension, but is slow to re-lace and trim up. I added a nylon rope seam to keep the holes from tearing out. Flimsy. The silver marine vinyl is not as strong and the black material used for the bra. I put a single piece of white HDPE right in front of the steerer directly behind the rear bike wheel as a deflector shield.

Rear-top view; dovetailed the end to make it nice and roundy.

Rear-left-side view; the whole rear end is roundy and aero.

Rear view. I realized a bit late that changing the tire my pose a problem. Otherwise, the tire is completely covered from throwing spray into the trailer; it’s not moisture-proof, but it’s better than a poke in the eye.

What you don’t see is the bottom; it’s one seamless piece with only a couple of zip-ties protruding through to suspend it from the frame. I figure if I get to about 80 mph there may be some lift generated!

Interior

Top view with the ebike off to the left (out of the picture). Two Sears Craftsman tool boxes hold 30 little LiPo bricks each. There has to be 3 pounds of copper linking them altogether. Okoume Marine plywood, about 5mm thick and sealed with stinky stuff is used for the decking. Beneath that is a pair of Aluminum Angles running the length on both sides. These are tied down to a CrMo Steel tube passing through the Bottom-Bracket (I call it the “Truss”). About 40% of the batteries are sitting on the truss, and the rest of the weight is on the hub axle. Kinda hard to see though the HDPE sheeting is covering the tire to protect the trailer contents from overspray – and acts like a barrier to prevent the bags from rubbing against the tire and spokes. (I hates it when it does that!)

Top view near the rear; there’s more space here to plop in two more bags behind the battery boxes.

¾ Top-View with my gear beside the trailer. Good view of the steering dampener.

And there it is all loaded up in no time! This was by far the fastest part of the project: Quick load and unloading.

All done for now. Still needs buff and polish – but that will have to wait until there is opportunity on the road – or whenever I can get to it.

Better pics later when I’m on the road.

ADDENDUM: Integration issues -

• I thought that I had an extra pair of turn indicators because I discovered too late that they are pretty cheap quality and break easily; alas I only had 3 pairs with one being bad. Thus the went without, however it is wired for signals and 3.3V for Blinkies (which I ran out of time to install).
• However - the running taillight and Brake Light do work!

Cheers, KF

 

[dbaker]

Great job, KF

 

[Kingfish]

Great job, KF

T'anx pal

I just wanted to add that the battery box installation used a thin strip of aluminum 1/32 x 3/4 wide x 15 long Qty-2 down each side, with #8 Phillups-head (grrrrr ~ we hates them) and washers to secure it to the framework below. (Apologies - no pictures) The aluminum strip adds reinforcement and spreads the load to the box sheetmetal - creating better resistance to having a fastener pull through. Between the thin strips is a section of 5mm Marine Plywood which nearly equals the total height of the fasteners and strip. Then I laid down a thin layer of closed-cell foam; this will deform/conform to fill the voids and provide narrow frequency dampening. The last layer is Yellow (naturally illuminating under low-light) HDPE which I used to provide the last layer of armor against a protruding fastener. Because of this slight layering - about 9mm total - there was not enough room in the battery box to place a 4th row. Therefore I could only fit 30 bricks a side. The 4 spare batteries will travel elsewhere (tbd this AM).

Fueling up (coffee... we need more coffee) KF

 

[Whiplash]

Soooo, did you launch it? I love the idea of the trailer rather than the goofy long tails you see here. I would love to do a small geared hub on a trailer FULL of LIpo to do a big ride and just have my gear drive there for emergency! Looks fun to me! I hope it works out well!

 

[Kingfish]

Soooo, did you launch it? I love the idea of the trailer rather than the goofy long tails you see here. I would love to do a small geared hub on a trailer FULL of LIpo to do a big ride and just have my gear drive there for emergency! Looks fun to me! I hope it works out well!

Thanks Whiplash for the positive thoughts.

I was going to do a summary when it was all said and done. The short story though is that the trailer had problems in this incarnation. I am at present remanufacturing (or resurrection) as a simple trailer w/o the motor.
Link to description of problem: On the Road: Going to California: 2011 (probably should be renamed On the Side of the Road: Going to California )

• As a Pusher, this frame is not suitable for heavy load; light-to-medium loads are OK. However the design WAS for heavy load. The axial twisting results in the trailer steering the eBike into traffic or to the curb and oscillating without control.
• In the rework process, I removed the motor and mounted it on the eBike. The custom axle used for the Hitch assembly is now going to become of the trailer’s rear axle because a standard axle isn’t long enough. The signals and battery cabling can be saved; I shall put some batteries on the trailer though not the full complement as originally planned.
• The load will be reduced from 100-130 lbs. to something more in the realm of 35-50 lbs.

Below are pictures of the assembly at launch from last week.

Top View: Note that the right pannier is not mounted (cos I have the camera out).

Rear ¾ View: I was impressed. :lol:

We are still carrying a candle of hope and optimism that this design can be saved, though not as a pusher trailer. For that I think we either need to swap out for a steel frame and/or redesign from scratch a purpose-built framework.
~KF

 

[Whiplash]

Looks good though! What is with the propeller?? LOL! Trying to get a little regen there?? HAHA..

 

[LI-ghtcycle]

Stunning beautiful work!! 8) 8)

How did you join the HDPE? Glue, welded or?

Love the white/silver/black too, very well done.

 

[Kingfish]

Gosh <kick pebble> you guys are awesome!

Propeller: Yesh, of course it’s fer regen :wink: <hic *> Dat’s my bling yer talkin’ about there buddy. I think it helps to have a wee bit of humor. The front of the eBike sports a nerf pad just below the faring that says “Hot Wheels!” :lol:

Tonight I bellied-up to my local Teriyaki grazing trough and this old guy came in pushing a shopping cart wanting to know where he could buy my bike and how much was it. He said that my “Hot Wheels” model was very attractive but couldn’t find the manufacturer branding. I told him it was a prototype and that it’s not for sale. He was bummed out but thanked me for sharing the information about the bike. In return he told me this joke:

• “What do you call a dog with no legs?”
  I was about to answer that I didn’t know, and he said “Doesn’t matter; he won’t come to you anyway.”

Bada bing bada boom

HDPE: Copious amounts of 8” Cable Ties (I call them zippies). I used a hole punch made for leather, or my soldering gun to create holes through the HDPE. Not so great for the soldering gun and I highly recommend a well-ventilated area if doing so.

The bottom is one single piece of HDPE with a cutout for the tire; this hides a lot of air drag. The sides are folded up and create a bonding surface for the sides which are cut from one 2x4 sheet. The top is made from a single 2x4 sheet as well; I draped it over a loaded trailer to get the approximate shape, and then cut the vinyl to match. The holes in the vinyl were burned through with the soldering iron. The hem has a bead of 3/16 marine-grade Nylon-Poly rope inside to prevent tearing. I am not sure though that the vinyl material is strong enough. The white rope is fastened at the bottom by passing through the Cable Ties that secure the side walls to the bottom HDPE. The whole design is a little sketchy; good for one trip. I plan on taking repair materials just in case.

Colors: You know – I just have this thing about Design; in college I had a double-major as an undergraduate: Art & Engineering. I love to draw and illustrate, and I like wrenching on motors. Put those two skills together and you get a Design Engineer, of which I yam. My early career was as an Electromechanical Design Engineer, but then computers came out about the same time, and I knew how to package products, design circuit boards, and so forth – pretty soon I’m building computers for my pals, then I landed a contract with the DOE to provide high-speed CAD workstations on top of my labor contract. I became adept at scripting AutoCAD; pretty soon I am creating 3D models and doing animation, then video, and this lead to multimedia programming, then web development. I’ve been contract-programming up the hill off-and-on for the past 18 years for a tiny lil’ squishy company in Redmond, often hired to specialize in User Interface; go figure. :lol:

I like Black; it hides a lot of visual issues and it’s attractive. Last year’s faring was Black and Yellow to match my clothing. But in the winter I decided I wanted White for better visibility when it’s pitch black and chucking down rain and sleet. The Silver is in lieu of reflective tape on the covering.

It also reminds people that I could be police! I have had people react strangely – and even had one pull over when they saw me and the flashing red blinkies. If only I had a siren; what trouble could I get into?

MHahaha! KF

 

[Kingfish]

The Foam Treatment

On the other thread we discussed ways to reduce or eliminate the wobble of the trailer which it still has even after the motor was swapped out for a regular tire and the weight cut to 1/3. Last night I came up with an idea to use structural foam, or more exactly – spray foam. Home Depot had this stuff. I decided the < 1” fill stuff would be more useful; a denser yield.

The trailer was stripped of the frame. I then prepped it by taping off the important sections, such as where there are threads, and where there are bearing surfaces. I also taped off a couple of vent holes to force the foam farther down. Tubes were inserted so the foam could be applied to the farthest reaches of the top, seat, and down tubes, and the lower stays. There is no way to know if the upper stays would receive foam.

Stripped and laid out.

Stuffed the little adapter into the lower stay. Stuffed plastic where I wanted to block the foam. Taped over some vent holes.

Tape covers threaded sections. Filling extension in place for Seat Tube and Down tube.

Same for Top and Down tubes via the Head tube.

The actual process of adding the foam wasn’t terribly difficult, just slow and messy. When they say to wear gloves – it is best to do so for this stuff sticks worse than superglue to the skin, and Mineral Oil, Turpentine, Paint Thinner, or Alcohol do not cut it (although I recall seeing stuff at Home Depot that could – I just didn’t think I’d need it). If it does contact your skin – try to wipe it off right away – but don’t touch anything else; just let it dry and you might be able to peel it off… maybe.

I filled and filled and filled the voids. Eventually I saw proof that the voids were indeed full and then I pulled the tubes. This is unfortunately about 10 minutes too late cos the foam keeps expanding.

Awefully messy. Don't touch anything with foam oozing out of it!!!

The can says it’s ready to touch in 15 minutes: They are liars. If you touch it – it will stick to you and you will have to wait a week for your skin to exfoliate before it is removed. It is best to wait at least two hours. Do not peel off the little blobs; leave them be! If you peel them off early – the stuff in the center will start to expand and you’ll need to wait all over again. The can says it will dry rigid in 8 hours. I think it’s best to wait a day. There’s no way I can work with this stuff until the morning and I think it will take me two hours to clean up the frame before I can put it back together and see if it will work. I have no doubts that some wobble will be attenuated – it’s just a question of how much and will it be enough.

Stay tuned for the continuing saga of the little trailer that wobbled before it could roll.
~KF

 

[dbaker]

Well done, KF I wondered how you would inject it and this way you made sure to get them completely full

 

[TylerDurden]

That stuff is nasty. It also requires significant exposure for the ambient moisture to make it cure. The deeper fills may not cure for days.

Not that it will matter too much, the stuff has little tensile or torsional strength.