Wednesday, October 16, 2013

Postal cargo trike

While in Denmark I had an idle moment in the presence of a postal Nihola.  The postal service in Denmark has purchased perhaps a couple of thousand of them.  Its an interesting design, and the parts that they didn't change from a regular Nihola are interesting to note.

A postal Nihola is mostly a standard model with a different front end.

Basically the front is swapped out for a float-loading platform, there is some modification to the frame where the rider steps over, and the rear has a gargantuan cargo rack bolted on.  They use an electric-assisted derailuer system, with what looks like an above-average motor, rim and tire.  But importantly, the rear frame and steering are hardly changed from a regular "little" Nihola.

The rear rack is epic, and the frame is modified for a lower stand-over height.

Also interesting is that they didn't go with a classic box box trike like Christiania.  They have a small number of such trikes already, and apparently did not find them to be the right choice.

Sunday, October 13, 2013

Flats, continued

So its great to save the world by riding a bike, but flat tires are a bit of a barrier that it seems cars have more or less gotten past, while bikes have not.

So, we have just been visiting Denmark the past couple weeks, and we got there by using the Oslo to Copenhagen ferry.  The price to take a cycle on board... a cycle of any size.... is negligible after the price of the humans.  So we just load up two cargo trikes and pedal over to the ferry, and the next day we pedal off again in a new land.  Mindful of the risk of flats, I packed two fresh new tubes for those troublesome front tires.

We did maybe 150km a week going around town on a Nihola and a borrowed bike without a problem.  Then on the way back, we got two flats on the same tire within a few kms.  While on the way to the ferry to leave the country.  This was of course a front tire, on the right.  Not usually high pressure, not unusually heavy load, the same Schwalbe Marathon Plus 20" tire that has been there all along.

Small metal object, sharp on one end.

Nice sharp bit of glass.

There was a silver lining on this.  I found that we have a lock that works great for lifting the front tire.  Just set the parking brake and use the lock as a leg, in this case under a front corner of the box.

Using a lock to hold the flat tire off the ground while the repair is made.

Monday, October 7, 2013

Gearing basics

I think its safe to say that appropriate gearing on a cargo bike/trike is more important than the gearing on a lightweight bike.  The following gear chart can go a long ways towards finding a good gear ratio.  I started making it shortly after we got our first Nihola and have been using it ever since to choose sprockets.

A bike gear ratio chart with 19 gearing systems and wheel combinations.

The green lines are what I believe are official default Nihola ratios.  Red lines are the ratios I have personally put some distance on.  Some of the grey lines are from commuter bikes I have ridden, and others are just there because they have something to show.  There is even a road bike.

The most important thing to see is that a particular gear hub can appear multiple times because the front and rear sprockets determine the output ratios in combination with the hub itself.  The Nihola company and I disagree on what sprockets are appropriate to fit.  I think they are choosing ratios that make it impossible for normal riders to get any use out of the highest gears.  (I don't consider racing downhill to be useful.)  Lower ratios can always be put to use.

Another important point is the "range" of a gearing system, that is, the highest ratio divided by the lowest ratio and expressed as a percentage.  For an SRAM P5 of Shimano Nexus 7 this is about 250%, for a SRAM S7 or Shimano Nexus 8 / Alfine 8 this is about 300%.  A bigger range means a bigger difference between the fastest and the slowest gears.

It is possible to fit a derailleur gearing system on a Nihola, possibly even with multiple chainrings in front.  This can provide a huge gear range at a reasonable cost, but can leave the rider in a difficult situation because ratios can only be changed while moving, and its easy to end up not moving when trying to take on a steep hill.  The Danish post office has a couple thousand derailleur-electric Nihola postal trikes which seems to be working well for them, but they aren't climbing mountains.

In my opinion, the best general-purpose gearing system for a Nihola is a Nexus 8 or Alfine 8 with the standard 38-tooth sprocket in front, and something like a 24, 23 or 22 tooth sprocket in back.  A strong rider will run out of gears when empty on flat ground, but that should be at least 25km/hr which is tolerable for a cargo trike, in my opinion.

Saturday, October 5, 2013

Cake, curbs, and paint

Three items for today's post.  First of all, when carrying cream cakes in a Nihola, don't let them bounce around in the bottom of the cargo box.  Put something soft under them.

Ohh, thats a sad thing to see.

Next up, and unrelated to the cakes, I have determined that a good low gear ratio allows some really nice curb climbing even while loaded.  Without any particular effort, I drove something like 40kg of kids and crap up the curb shown below.  I'm estimating it was 5 inches.  Go slow, one wheel at a time, at perhaps a 45-degree angle, but steer into the curb at the moment of climb.

Finally, the paint quality of a Nihola.  I don't know anything about paint really.  I'd say that the quality seems to be pretty good.  It is thick and evenly applied.  I have seen no defects in the paint of either Nihola.  However I have been able to damage it many times.  In particular, the top rim of the box is easily hammered by metal objects being carried, which quickly takes care of paint.  Secondly the front-bottom edge of the box can easily be run into things; a nice rock will also take care of paint without trouble.  The third issue is on the dropouts.  This is the biggest and most annoying problem.  Here I have seen large flakes come off, and it seems to be impossible to avoid damaging the paint if the wheel needs to be removed.

For our black-framed Nihola I got a small can of black paint which I use for touch-ups.  The orange-framed Nihola just gets treated real nice, but the dropouts have now started their inevitable journey towards large scale paint loss (and re-touching).

Paint loss has started.

Advanced paint loss, loose chips removed, prior to a quick sanding and painting.

On the positive side, it seems the frame (especially around the dropouts) does not rust aggressively.  I imagine that nearly all of the many thousands of Nihola owners in Copenhagen ignore it completely.