Tuesday, 28 February 2017

Specification vs Strategy

Specification vs Strategy 

What is the difference between a Specification and a Strategy?



the act of specifying.
Usually, specificationsa detailed description or assessment of requirements, dimensions, materials, etc., as of a proposed building,machine, bridge, etc.
a particular item, aspect, calculation, etc., in such a description.
something specifiedas in a bill of particulars; a specified particular,item, or article.
an act of making specific.
the state of having a specific character.



  • 1A plan of action designed to achieve a long-term or overall aim.
    ‘time to develop a coherent economic strategy’
    mass noun ‘shifts in marketing strategy’
  • 2mass noun The art of planning and directing overall military operations and movements in a war or battle.
    ‘he was a genius when it came to military strategy’
    Often contrasted with "tactics" (see tactic)
    1. ‘non-provocative defence strategies
  • 2.1count noun A plan for directing overall military operations and movements.


Whilst a a strategy may explain what you are intending to do, a specification will describe how you are going to do it. 

Surface Water Drainage Strategy 

Thursday, 23 February 2017

Rigid Forks for Commencal El Camino

Rigid Forks for Commencal El Camino - Intro

The Commencal El Camino Frame has lots of mounting points for fenders / mud guards, racks etc. and as such make a great rough stuff touring, utility frame. To increase loading option still further, you may consider rigid forks from surly or salsa. But what length of fork is right.

Rigid Forks for Commencal El Camino - Axle to Crown

The axle to crown measurement is the one to look for. This is some time listed as AC or A/C. It is the measurement from the axle to the crown of the fork, the crown is where the crown race sits.

The Commencal El Camino full bike is supplied with a RST Blaze 27,5" Fork, the  axle to crown measurement for this fork is 495mm.

Rigid Forks for Commencal El Camino - Sag

When you hop on a bike with suspension forks the forks squash down a bit. This is called sag. Racing bikes are set to have about 10% sag, whilst non-racing bikes might have 30% sag. An average of 20% is usually used. So if you apply this sag figure you are looking at a length between

  • 445mm (10%)
  • 396mm (20%)
  • 346mm (30%)
Bear in mind that the radius of a 650b wheel is 325mm. So allow for clearance, fenders, and mud space. 

Rigid Forks for Commencal El Camino - Shopping

Most forks available from surly or salsa are at least 460mm in length. It is better to go longer than shorter, perhaps adopting the 10% sag figure from above. 

So based on the above we would be looking at the below fork options.

  • Surly Instigator (447mm) - Lots of mounting points. 
  • Thorn Mount Tura (430mm) - No disc brake. Lots of mounting points.
  • Thorn Nomad Disc Fork (420mm) - Excellent Choice. 
  • Gusset DJ26 Fork (430mm) - Cheap. But no mounting points. 

Rigid Forks for Commencal El Camino -  Good luck.

Have fun and cheerio. 

Monday, 20 February 2017

Thorpy's Guide to Rigid Forks

Thorpy's Guide to Rigid Forks - Intro

A great many of the features on modern mountain bikes are aimed at racing, and going really fast and doing stunts and stuff. People used to do all this stuff on rigid forks, and probably break their wrists in the process, but now we have entered the marvelous age of suspension forks.

BUT if you are a luddite, troglodyte or hairier than average you may want to stick with a rigid fork. But where does this leave you? Can you buy a frame that is design for massive 150mm travel suspension forks, and run rigid forks on it?

Exec. Summary - If you are running a high travel 26er or 650b, you will likley be able to find a long rigid fork to replace, but for a long travel 29er, you will struggle to find a mass produced fork to cover forks above 120mm travel.

I have produced the below table to help you decide method used is to follow (click to enlarge).

Thorpy's Guide to Rigid Forks - Length Matters

Obviously you will need a fork that fits your wheel, but there is also the ride characteristic of the bike to think about. 

An over long fork will give a "slack" ride. Some people actually like this as it makes for a relaxed steering feel. However, and fork that is too short will result in a steepening of the head angle of the bike, and the steering will become "twitchy". Unless you a slightly delusional and masochistic this is not a very nice thing. 

As you change the height of your bike front, it pivots around the rear axle. This means that sever changes in height at the front end will change the position of the pedals relative to the saddle, the taller you have the saddle set, the more difference this will make. 

Thorpy's Guide to Rigid Forks - Travel

The bike below has 150mm travel suspension forks. The frame was designed (i should think) to run with forks of this sort of size, because it looks really cool. . . and some other reasons.

There are a lot of reasons why you might want to run the above frame with rigid forks. The list is long, and might includes mounting panniers or fenders / mud guards for a practical use, whilst still allowing for the use of high volume (fat) tires and a low step over height.

But can you really put rigid fork on a bike like this? Of course you can but do some maths first.

Thorpy's Guide to Rigid Forks - Maths for 27.5"

The above bike takes a 150mm fork. We need to find the "axle to crown" measurement for that fork, or any other 150mm travel fork, of the same wheel size, which in this case is 27.5" or 650b.

If we look at Axle to Crown Lengths for 150mm travel forks is we can see that axle to crown length is typically around the 550mm mark.

So we will need to find a rigid fork the same length?  NO

We also have to account for "Sag". This is when you sit on a suspension bike and it squashes down, under your weight. For different travel forks you would apply a different sag:

  • 100mm = 20%
  • 120mm = 25%
  • 150mm = 30%

So for a 100m travel fork, you would subtract 20mm. And for the above bike we would subtract 30% of 150mm . . . .  45mm . . . which give a rigid fork length of 505mm (for the above bike).

What sorts of forks are that length?. . . , not many:

There are some high end fork with 500mm axle to crown measurements such as the:

  • 3tcycling rigid-500-mm-team (tapered headset - see below)
  • Carbon Cycles Exotic 49cm

Thorpy's Guide to Rigid Forks - Headset

So you can get a fork the right length, you now need to attach it to the bike.

Some of these bikes designed for high travel forks have a 44mm headset in which case you may already to running a straight steerer tube (Commencal El Camino), but a 44m headtube can also accept tapered forks, the above list are not tapered forks (although you may find some which are).

If you have a tapered headtube, then you may need to fit an adaptor to allow for the 30mm crown race on the above forks.

Thorpy's Guide to Rigid Forks - Mega Table

Based on the above method please find below table showing required fork lengths.

Travel 100 120 150
Wheel  Sag % 20% 25% 30%
Axle to C
26" 440 490 540
Sag 20 30 45
26" w. Sag 420 460 495
27.5" 470 510 550
Sag 20 30 45
27.5" w. Sag 450 480 505
29" 480 520 560
Sag 20 30 45
29" w. Sag 460 490 515

In general I would recommend choosing a slightly longer fork (10mm - 20 mm), rather than a shorter one. A shorter fork will result in twitchy steering. Feel free to browse for forks of the correct length, but you might opt for:

Yellow = Gusset Jury 29er or Surly Karate Monkey

Green =  Thorn Mount Tura (26")

Orange = Surly Krampus (483 mm) Salsa Fire Starter (483 mm)

Blue = Exotic 29er

Thorpy's Guide to Rigid Forks - Conclusions

Is you are riding a high travel 29er then you may well have to suffer a drop at the front end (shorter  forks) in order to swap over to rigid. However, for most other bikes with 120mm travel or smaller wheels, you will no doubt find an off the peg solution. 

Thorpy's Guide to 44mm Headsets

1 - Thorpy's Guide to 44mm Headsets - Intro

The 1 1/8" headtube has been a constant in my life for the last several years, and I have enjoyed that constancy. Unfortunately, some clever people have decided we all now need a 44m headtube, which is bigger than the "old school" 1 1/8" headtube. The redeeming feature of the 44mm headtube is that it will accept 1 1/8" straight steerer forks, and 1 1/2" taper forks. Provided you choose the correct headset. So:

Good News - You forks will 95% likely fit.

Bad News - Choosing the Headset will be tricky.

Skip the Waffle? Scroll down to Sections 5 and 6

2 - Thorpy's Guide to 44mm Headsets - Sheldon Brown

First stop of information is Sheldon Brown's excellent website. But when you consider the variety of 44mm headsets for sale on the internet, the below list of just 2 options seems a little short.

Even Sheldon does not have all the answers. . . . 

3 - Thorpy's Guide to 44mm Headsets - The 44mm Family

The frame I was upgrading to, said is requires a "ZS44 Semi Integrated". A quick search for this term will bring up a selection of suitable headsets, however I was still curious as to what is a "ZS44". I came across a very handy PDF published by problem solvers:

44mm EC or ZS? - What is that?

The above paired letters EC or ZS may precede the "44" in any 44m headset, and this relates to whether the headset will have:

  • External Cups (EC) - Like most Older Headsets
  • Zero Stack (ZS) - Think trendy.
The important difference from here on in is that the lower headset can be designed for:

  • 1 1/8" - For the upper cups.
  • 11/8" OR 1 1/2" for the lower cups. To allows for 1.5" taper on modern forks.

4 - Thorpy's Guide to 44mm Headsets - EC or ZS

ZS or Zero Stock will normally be for the upper / top or the lower / bottom of the headset.

Whilst the EC or External cup is generally only used on the bottom.

5 - Thorpy's Guide to 44mm Headsets - For Straight 1 1/8" (1.125") Steerer

Choose the following:

ZS44/28.6 - For the top.

ZS44/30 or EC44/30 for the bottom. (30 relates to the 30mm crown race).

A note: The EC bottom cup set up will add about 10mm in height to the front of the bike. This may result in a "slacker" ride, and can be useful to make up height if swapping from high travel suspension forks to rigid forks. 

6 - Thorpy's Guide to 44mm Headsets - For Tapered 1 1/2" (1.5") Steerer

Choose the following:

ZS44/28.6 - For the top.

EC44/40 for the bottom. (40 relates to the 40mm crown race).

7 - Thorpy's Guide to 44mm Headsets - Conclusions 

The 44mm headset is here to stay, as it allows the use of both straight and tapered steerers. However, you will need to spend a bit more time thinking about what combination of headset parts you need.

Many shops now supply 44mm headset parts on a mix and match basis, so you will need to know more than just the one number. 

The flip side of this added complication is that if you buy a frame with a 44mm headset, you can run pretty much any fork in it. . .  .for the time being. . . . .

Monday, 13 February 2017

Build a BMX EBike

Build a BMX EBike  - Intro

If you are looking for a cheap bike to convert in to an ebike, then a BMX can make a good option. They are tough, small and soon fall out of favor with maturing kids, meaning then can be picked up very cheaply on ebay, and small ads.

Perhaps the biggest advantage is the small wheels, which on a ebike means greater torque (for a lower speed) for a motor of a given power.

BMX Ebike - Quirky . . . 

This makes them ideal for modifying for BMX cargo bike applications.

Build a BMX EBike  - Ebike Kit

Order this first as delivery can be slow.

The cheapest way to get the motor throttle and controller is to order it directly from china. This could cost as little at £150 / $250 with postage.

If you live in a flat area go for a direct drive hub motor, or geared in a hilly area. Choose a power level that is legal (for road use) or to suite your application. Choose upwards of 750w from off-road use.

My bike (orange) uses a MY1020Z motor, a chain drive option on the front wheel. A hub motor would be a better idea.

Build a BMX EBike  - Batteries

Lead Acid are a cheap option, but they are heavy and short lived. Lithium are expensive. Battery choice comes down to budget. Buy what you can afford. Battery voltage should match your motor / controller voltage.

Build a BMX EBike  - Mounting the Battery

Finding a spot for the battery is tricky. BMX frames are small, and finding spot that will not result in problems is . . . .tricky.

Ebike BMX - Battery Mount Options - 2016
"Perfected" - 2018

Rear Mounted 

If you mount the battery at the rear, it will have to be thin and long in shape, so as to sit between your heels. If the battery is wide and square it will have to be set very far back, other wise your heels will hit the battery when you pedal.

Mount High at Rear to Avoid Heel Strike

Front Mounted

The few BMX ebikes which you see on the web, typically have the batteries mounted towards the front of the top tube. As you can see below I have welded a "basket" to put my bulky battery in. But you could use webbing pouches, or for light lipo (lithium polymer) packs, even duct tape can be used!
A lead acid set up, using a none welded bracket.

To be sure my choice would work I taped a cardboard box of a similar size in to position and cycled around to see if it got in the way.

Build a BMX EBike - Comfort

For comfort I would suggest fitting a maximum length seat post (400mm) if you are reasonably tall, and raising the handle bar height as tall as possible. I welded extra length in to mine, but you could fit some "chopper" handle bars for the same effect.

High Chopper Handlebars - Can increase comfort.

Build a BMX EBike - Tires

You will get more range from your battery using smooth tires. Knobbly tires on road being the worst option. If you are using the bike for practical reasons, why not install some tire slime / sealant so you won't get punctures.

Build a BMX EBike -  Limitations

If your are keeping pedal power just for the sake of legality, then a BMX is a good choice for the above mentioned reasons, but if you intended to do a lot of pedaling or need gears then opt for another type of bike.

Carrying stuff in panniers etc. is also tricky. Heel strike at the rear of the bike being a real problem. A saddle mounted bag might be an option for small items.

The main problem with this design is the lack of weight on the front wheel. This if ine over flat ground but a gravel uphill section will cause problems.

Environmental Consultants London

Environmental Consultants

Environmental Permitting

Monday, 6 February 2017

Notes on MY1020Z Motor

Notes on MY1020Z Motor - Intro

This is a fairly inexpensive geared motor made in china. It can be run at least up to 48v. I have tried 48v, and also 24v.

The MY1020 is a ungeared version of this motor, whilst the MT1020"Z" has reduction gearing.

Notes on MY1020Z Motor - Controllers

Yiyun Controller I have found to be good, very simple and reliable. I have used 350w (24v), 500w (24v) and a 800W (48v) variants of this with the MY1020Z.

MY1020 Mounted on Cargo Trike

MY1020 - Mounted in front wheel of cargo bike.

Notes on MY1020Z Motor - Performance

The MY1020Z is sold advertised at wattages ranging from 450w to 600W, it will take a lot more wattage than this. My MY1020Z has spent its life driving a front wheel driven 20" wheel ebike. At 24v 500W this will pull bike a rider up a steep hill at around 7 mph, but owing to a reduction in revs, the engine heats up. Some pedalling is required.

This was achieved with further reduction gearing with the 11 tooth sprockets linked with a 24 tooth freewheel.

This 11 to 24 tooth reduction was also used with the same setup, but with 48V 800W controller, this delivered much speed with little increase in torque.

The above setup would be useful in flat areas of the USA, where this wattage is just about legal. But in the UK, it would be advisable to lower max speed to 15 miles per hour.

This would require an 11 to 48 tooth reduction, to give a 15 mph approc top speed.

Notes on MY1020Z Motor - Chain Gauge

The M1020Z comes supplied with a large gauge sprocket, commonly used on small scooters etc. But sprockets for bicycle chain can be purchased from TNC Scooters.

Notes on MY1020Z Motor - Alternatives

For a more refined, efficient and altogether better choice I would recommend and Bafang BPM 500W.

Notes on MY1020Z Motor - Conclusions

Working in it favour the MY1020Z is a simple motor that is easy to wire, and provides good level of power if used with the right controller and battery. Owing to the fact that it powers a chain (rather than the wheel directly like a hub motor) this gives freedom to choose gearing. 

However, it is rather heavy. You will probably need to be able to weld in order to fit this to a bike, as it will require a sturdy mounting point. Its size on a bicycle will make it stick out of the side considerably.