Gas station without pumps

2019 January 23

Mediocre experience at the local bike shop

Filed under: Uncategorized — gasstationwithoutpumps @ 11:24
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My bicycle was in need of some care this past weekend (bald tire, worn brake blocks, worn chain), so I decided it was time for a tune-up.  I usually do all the work on my bike myself, but the closest bike shop to me (now called CycleWorks, previously Sprockets) has changed hands repeatedly in the past few years, and I am a bit worried that they may not last long.  So I decided to spread the wealth a bit and pay for a tune-up.

I called them up to see if they could do a tune-up over the weekend—I wanted the bike for commuting on Tuesday (Monday was a holiday).  They said that they were closed on Monday, but if I brought the bike in on Saturday, they could have it ready by Sunday, unless it needed some part they didn’t have.

I brought the bike in on Saturday shortly after they opened at 9 a.m. and explained what I wanted.  The only unusual request was that I wanted the packing grease removed from a new chain and replaced with a dry lube like White Lightning or T9.

Early in the afternoon on Saturday, they called me and said that the bike was ready.  The promptness of service was quite pleasing, and they did seem to have used dry lube on the new chain.  I ran a few errands on Saturday, and found that the brakes were not well adjusted—the cables were loose enough that I was almost bottoming out the brake levers before the brakes engaged.  I could fix it with the barrel adjusters, but I used up almost the full travel on one barrel (which should be reserved for wear on the brakes, not the initial adjustment).

Tuesday morning, on my way up the hill, I shifted into my lowest gear and the chain came off into the spokes.  It turns out that they had the rear derailleur adjustment off by a full index step and they hadn’t set the stops on the derailleur correctly.  This is the sort of problem I would expect of an amateur or a new trainee, but not from a professional bike mechanic I was paying an $80 labor fee for.

This morning I took half an hour of my time to adjust the brake cables and the rear derailleur correctly, also doing a little truing of the rear wheel to keep the rim from rubbing on the new brake blocks.

I won’t be going back to CycleWorks for a couple of years—time to give them a chance to hire or train competent staff (or go out of business).  I’ll have to try the next closest bike shop, which is 0.2 miles further away.  (Santa Cruz is blessed with an abundance of bike shops, which makes it fairly easy to find one that meets your needs and your tastes and is within walking distance—for years Sprockets was a good match for me, but CycleWorks doesn’t seem to be.)

2016 October 24

Bike seat fixed

Filed under: Uncategorized — gasstationwithoutpumps @ 18:47
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This past weekend, I fixed my bike seat (see Broken bike seat and Flexible adhesives).

The idea of the fix was simple: to insert at 15mm diameter aluminum rod (6061 alloy, tempered to T6) that spans the break and the high-stress point on the other side of the clamp, which is also scored and likely to fracture, and glue it in place.

I found the rod I need at McMaster-Carr, with specifications of 15±0.23 mm diameter.  I thought it was slightly undersized at 14.7mm, measuring with my calipers, but my calipers are not so precise that I can be sure of that measurement.  Measuring with my micrometer gave 14.82±0.01mm, which is within spec.  I could have gotten a more precisely specified aluminum rod for an extra $10, but I did not think that it was worth the extra price—I may come to regret that, as the aluminum rod fits loosely, not snugly inside the tubing.  I cut the rod to length with a hacksaw (using oil to lubricate the blade) and ground the sharp edges down with a wet wheel, then sanded the rod both to round the ends and to remove most of the oxide coating and provide a rough surface for the epoxy. The rounded ends are to reduce the stress raisers at the ends of the rods, as that is now where the tubing should flex the most.

Aluminum rod: cut, ground, and sanded. The mark indicates where the break in the tubing should be.  The rod extends about 15mm past either end of where the clamp holds the tubing.  I would have extended it further, but I was worried about bending the aluminum tubing too far to open up the bike seat frame enough to get over the end of the tubing.

Aluminum rod: cut, ground, and sanded. The mark indicates where the break in the tubing should be. The rod extends about 15mm past either end of where the clamp holds the tubing. I would have extended it further, but I was worried about bending the aluminum tubing too far to open up the bike seat frame enough to get over the end of the tubing.

I sanded the inside of the tubing on the broken bike seat and the fractured ends to promote adhesion, and I cleaned both the rod and the tubing with rubbing alcohol.

In the comments on Broken bike seat, gflint suggested a silicone adhesive, but I ended up using a flexible epoxy, TotalBoat FlexEpox, that is designed for repairing boats.  It is supposed to adhere well to aluminum, have high tensile and flexural strength, and a very slow set time, plus it is fairly cheap at $18 for about 30 times more epoxy than I needed.

I mixed up tiny amounts of the epoxy in old cough-syrup measuring cups:

The cough-syrup cups did not make precision measurement of the resin and hardener easy, as both were quite viscous—I hope I got close to equal quantities. I suppose I should have gotten out the centigram scale and mixed by weight—that would probably have given a more precise ratio.

The cough-syrup cups did not make precision measurement of the resin and hardener easy, as both were quite viscous—I hope I got close to equal quantities. I suppose I should have gotten out the centigram scale and mixed by weight—that would probably have given a more precise ratio.

For the first gluing on Saturday, I coated both the inside of the tubing and the rod with the epoxy and inserted it to the desired depth. I wiped off excess (there was a lot that oozed out) with a paper towel wet with rubbing alcohol, and clamped the rod in place simple by letting the other part of the tubing press against the rod sideways. I used a little scrap of paper towel between the rod and the outside of the tubing to keep them from getting glued together:

The rod glued and clamped in place, with paper towel to keep the rod from sticking to the outside of the other part of the tubing.

The rod glued and clamped in place, with paper towel to keep the rod from sticking to the outside of the other part of the tubing.

On Sunday, I mixed more epoxy and coated the inside of the other piece of tubing and the piece of the aluminum rod sticking out, then lined up the tubing and let it close back together:

Excess glue squeezed out of the joint.

Excess glue squeezed out of the joint.

I clamped the joint together by wrapping bungee cords around the frame of the seat, and wiped off the excess glue with a paper towel moistened with rubbing alcohol:

The bungee cords provided a fairly large clamping force, but no more glue oozed out when it was added, so the springiness of the frame alone may have been sufficient.

The bungee cords provided a fairly large clamping force, but no more glue oozed out when it was added, so the springiness of the frame alone may have been sufficient.

On Monday, I worked on the clamp on the bike.

I rounded the edges of the clamp to reduce the stress raising that had led to the first failure—the edges had been quite sharp.

I rounded the edges of the clamp to reduce the stress raising that had led to the first failure—the edges had been quite sharp.

In addition to rounding the edges to reduce the stress raising, I also offset the seat by a few millimeters from where it had been, so that the glued joint is now slightly inside the clamp.

Before replacing the seat, I noticed that there was a bad rust spot behind the clamp, so I took the clamp apart to look at the frame:

The frame was quite rusty behind and inside the clamp.

The frame was quite rusty behind and inside the clamp.

I was going to sand the rust spots, prime with metal primer, and repaint the spots, but my metal primer was no longer any good, so I just did some light sanding and coated all the rusty spots with oil. I will have to buy some more metal primer and repaint in a couple of weeks when I next have time to work on the bike.

I put the bike seat back in the clamp and replaced the mesh seat, which had been washed to remove the road grime.

I plan to let the epoxy cure for another day before riding the bike (they claim a 7–10-hour cure time, 24 hours for high load, but I’ll go a little longer, as it is going to rain tomorrow anyway).

I’m hopeful that this fix, which cost under $50, will let the bike seat be usable for the next 15 years.

2016 October 13

Flexible adhesives

Filed under: Uncategorized — gasstationwithoutpumps @ 13:23
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I’ve started figuring out how to fix my bike seat (see Broken bike seat).  The idea is to insert at 15mm diameter aluminum rod (6061 alloy, tempered to T6) that spans the break and the high-stress point on the other side of the clamp, which is also scored and likely to fracture, and glue it in place. Originally I was planning to get someone to weld it, but that is looking like a bad idea—the heat-affected zone around the weld would lose 80% of its strength, unless the whole seat is retempered, which is a bit problematic with a powdercoat finish.  Also, grinding the weld down to the point where it is smooth enough to fit into the clamp would be difficult, and the result would again lose a lot of the strength.

I found the rod I need at McMaster-Carr, and it should arrive tomorrow, but I now need to choose an adhesive that is strong, flexible, and can cure in a thin film between the rod and the inside of the aluminum tube.

In the comments on Broken bike seat, gflint suggested a silicone adhesive, but most of the consumer ones are one-part adhesives that rely on exposure to moisture from the air to cure, which won’t work for a thin layer 10–15cm long between two pieces of aluminum.  There are two-part silicone adhesives that don’t rely on exposure to humidity for curing, but they are most marketed to industry, not easily available for one-shot end-user projects.  I don’t want to have to buy a $60 tool to apply the adhesive!

I started looking for flexible epoxies available to consumers.  Here is what I’ve found so far:

adhesive cost flexural modulus (stiffness) tensile strength flexural strength
TotalBoat FlexEpox $17.99 193,000psi 5,610psi 9,050psi
West System G/flex 650 $27.55 150,000psi ~2,000psi? or is that overlap shear strength?
Marine-Tex FlexSet $29.67 ? ? ?

Bob Smith Industries BSI-203H Mid-Cure

$8 3800psi
3M Scotch Weld DP-125 $41.52+applicator ? 3300psi (2200psi overlap shear) ?

There are undoubtedly many others (Bondo 280, for example), but I’m having a hard time finding any technical information about them. The costs are what I could find on Amazon.

Currently, I’m leaning towards the TotalBoat FlexEpox, which is cheap, has decent specs, and a slow set time, so I have time to reposition things.  I might have preferred a slightly more flexible glue, but I think this will work.

2014 July 28

New mesh seat finished and tested

Filed under: Uncategorized — gasstationwithoutpumps @ 17:50
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In Need new mesh seat for recumbent, I mentioned that I needed a new seat for my recumbent, as the one I’ve been using since 1999 (15 years!) is completely worn out.  I repaired the seat once before (replacing part of the front strap), but the seat was not worth repairing again, as the warp has worn away in several spots across the middle of the seat (apparently abrasion with the central strap behind the seat).

I bought new hardware and straps from Country Brook Design (through Amazon, since the prices were the same and the shipping seemed cheaper than a direct order from Country Brook Design.
I got

There was $7.08 shipping and handling on the order from Country Brook Design.

I also bought a yard of 840×1680 denier leno-woven mesh fabric from ahh.biz, but when I went to check the price again, it is now a “discontinued product”—I must have bought their last yard—including shipping the total bill was $20.20.

Since I already had sewing thread, the total cost for making the new seat was $76.11, but I have a lot of materials left over (the 25 triglide slides, 16 buckles, a little bit of seat-belt webbing and reflective webbing, and most of the leno-lock mesh).  I could have bought a seat from Greg Peek at Longbikes for $149.00 plus $15 shipping and handling, so making my own was less than half the price, despite having a lot of excess parts.  Also, my new seat has fancy red straps that are reflective at night, and the new straps are polyester rather than nylon, so should perform a bit better (less stretching, more UV resistant, faster drying).

I decided to use dual-adjustable heavy-duty buckles, so that they would be less likely to break and easier to replace if they did break (no sewing of the buckles). I also ran the 1” straps all the way across the seat at the top, bottom, and middle (3 of the 7 horizontal straps), as these seem to be the high-stress parts of the design (based on the stretching in the old seat).  I ran the warp horizontally, as I thought that would result in less stretching than having the warp vertical (as on my old seat)—I’ll let you know in 15 years how that works out (if I remember).

The new seat came out a bit heavier than the old one (545g rather than 470g), probably because of the straps across and heavier plastic hardware. The extra 75g is completely irrelevant give how much my bike and panniers weighs.

I used my wife’s sewing machine (my treadle machine needs a new leather belt, or tightening of the old belt).  My wife’s machine had no trouble with the mesh or the reflective webbing, but going through the seat-belt webbing sometimes caused it to have problems, particularly where it had to go through two layers of seat-belt webbing, a layer of reflective webbing, and the mesh.  I think that the treadle machine would have had less trouble, but I didn’t want to take the time to fix the belt on the treadle machine.

The seat came out looking ok, and I took a short ride on it today to buy groceries—it is as comfortable as the old seat and much nicer looking:

In this side view, you can't see much of the mesh seat—just the straps on the sides.

In this side view, you can’t see much of the mesh seat—just the straps on the sides.

From the front, the red straps match the red paint fairly well.

From the front, the red straps match the red paint fairly well.

By using a flash on my camera, I could light up the reflective straps even in the day time.

By using a flash on my camera, I could light up the reflective straps even in the day time.

From the rear, the reflective straps should add a fair amount of visibility at night.

From the rear, the reflective straps should add a fair amount of visibility at night.

The heavy-duty dual-adjustable buckles seem to work well.  By keeping the straps fairly short, I did not need to use the triglides or keepers to hold the ends of the straps in place—they aren't long enough to be a nuisance.

The heavy-duty dual-adjustable buckles seem to work well. By keeping the straps fairly short, I did not need to use the triglides or keepers to hold the ends of the straps in place—they aren’t long enough to be a nuisance.

2014 July 14

Need new mesh seat for recumbent

Filed under: Uncategorized — gasstationwithoutpumps @ 21:28
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I need to replace the mesh seat on my recumbent bicycle, because one of the buckles snapped yesterday. The mesh itself is badly stretched and abraded, and a few of the webbing straps are badly worn, so it is not worth repairing the seat—it’s replacement time. I can still ride the bike, but it isn’t as comfortable with the front strap no longer functional.

Now I’m trying to figure out exactly what fabric and parts to get.  One person on the Ryan owner’s club mailing list conveniently provided a parts list recently, though the seat I have currently does not exactly match his list (for example, I have all 1″ webbing, no 3/4″ webbing).  Here are some things I’m trying to decide:

  • What type of mesh should I get?  He recommended black Leno Lock mesh from Outdoor Wilderness Fabrics MESHBLK at $14.03/yard, but I’m also considering Phifertex Vinyl Mesh at $12.95/yard, which is available in many colors, or Phifertex Plus at $17.95/yard, which would provide less stretch, but also less ventilation. The Phifertex Plus is sold as a sling mesh (capable of supporting a person’s weight), but the others are not.  I suspect that any fabric rated for seats will have too little ventilation for the recumbent. The leno weave fabrics are likely to provide more stability in an open mesh, because the warp threads twist around each other, rather than running straight, locking the weft threads in place. The bentrideronline forum posts generally recommend the Leno lock mesh from Outdoor Wilderness Fabrics, so I’ll probably go with that, even though it is a bit too stretchy.
  • What sort of webbing should I get?  The edges of the seat use 2″ webbing to stabilize the seat and attach the straps, plus a couple of diagonals from the center front to part way up the sides, to support the weight of the rider.  The rest of the straps are 1″ wide.  But should they be nylon, polypropylene, or polyester straps?  Nylon has high strength, but is rather stretchy. Polypropylene has less stretch, but poor abrasion resistance and UV resistance, and polyester has the best UV resistance and the least stretch (about half as much as nylon webbing of the same weight under the same stress).  It also doesn’t absorb water, and is more resistant to mildew and rot.
    I can get black polyester 1″ webbing for about 35¢/foot, and 2″ black polyester webbing for about 75¢/foot, but colors are a little more expensive: I can get 10 yards of red 1″ with reflective stripes for $18.90, or plain red for $1.48/yard. For a bicycle application, the reflective stripes may be a useful safety feature. Red 2″ seatbelt webbing would be about $10 for 5 yards.
  • I also need to get buckles for the 7 cross straps and the two straps that go over the top of the seat.  I’m undecided between simple side-release buckles (Fastex FSR1 59¢), and dual-pull side release buckles (generic GTSRD1 47¢) from Outdoor Wilderness Fabrics. Cam lock buckles (generic GCB1 46¢) are also a possibility. I’ll also want a a tri-glide for each loose strap end (generic GTG1 12¢).

So, unless I can get a new seat from the manufacturer of my bike (Longbikes in Colorado), even though they discontinued this model about 10 years ago, I’ll probably be making my own seat soon.  It’ll cost me about $50–60 for materials, but I suspect that an already sewn seat would cost more like $150, and I wouldn’t have the option of red straps with reflective stripes.

 

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