Saturday, May 28, 2022

Bestrider Pump Pro 16: Assembly Completed

With the new 3 speed drivetrain on the Bestrider Pump Pro 16 completed, what is left is to put on the pedals for a test ride.

This bike came with pretty crappy pedals, so I had to get a better set of kids pedals for this bike. As discovered on the Early Rider Seeker 14, the Early Rider pedals are really good pedals, with smooth bearings and high quality finishing.

It is hard to find good aftermarket pedals for kids, as most that I have seen are cheap plastic ones that hardly even spin. Finally I managed to find these Early Rider pedals, but they are rather expensive.

New set of Early Rider pedals!

With sealed bearings, they spin smoothly.

133 grams per side, giving a weight of 266 grams per pair. 

Pedals installed on the Bestrider bike! After installation, I found that the pedals look a bit big relative to the crankarm.

Upon side by side comparison of the Early Rider pedals of the Seeker 14 and the new set, I found that the new pedals are larger!

So these are not the same pedals as those that came stock on the Early Rider Seeker 14. However, they look similar and are of the same high quality. I guess the larger platform means that it can be used even when the kid's feet grow bigger.

Upgraded bike! Can you spot the changes?

Nexus 3 speed internal hub installed on the bike.

Bell crank protrudes from the frame, but it can't be helped.

Cable routing is a little messier due to the additional shifting cable from the shifter.

2 finger braking is OK!

On the left side with no shifter, 3 finger braking is possible.

However, 2 finger braking is preferred, to be symmetrical with the right side.

Comparison with the Early Rider Seeker 14, after the upgrade.

On the previous comparison before the upgrade, the stock handlebar on the Pump Pro 16 was really high, even more than this.

Comparison of the handlebar area

Comparison of the drivetrain and rear wheel area. No more belt drive.

Under sunlight, the red paint on the new bike looks stunning.

The glitter in the paint looks really good.

Another picture showing the high quality of the paint job.

3 speed internal hub drivetrain!

Finally, let's compare the weight of the different setups.

Early Rider Seeker 14 (Single Speed, Belt Drive)
5.7 kg without pedals and kickstand, in stock condition.
About 6 kg with Early Rider pedals (200 g) and kickstand (~100 g).

Bestrider Pump Pro 16 (Single Speed)
5.6 kg without pedals and kickstand, in stock condition.
About 6 kg with larger Early Rider pedals (266 g) and kickstand (102 g).

Bestrider Pump Pro 16 (3 Speed)
After upgrading to 3 speed drivetrain, it is 6.4 kg without pedals and kickstand.
6.8 kg with Early Rider pedals (266 g) and kickstand (102 g).
This is also with carbon handlebar, Dura-Ace chain, new grips, etc.

In summary, this bike is now 6.8 kg after the 3 speed drivetrain upgrade. This upgrade added about 800 grams to the bike weight, including the offset from the lighter carbon handlebar, etc.

Is this additional 800 grams worth the 3 speed drivetrain? In this case, I think so, as 6.8 kg is still very light for a kids bike. Almost all other kids bike with a single speed drivetrain weigh more than this.

This 3 speed drivetrain means that there is always a low gear for climbing slopes, while gears 2 and 3 are for cruising on flat ground or even some sprinting. Overall, I am very happy with this new kids bike.

Bestrider Pump Pro 16: Inter-3 Hub and Bell Crank Installation

After preparing the Nexus 3 speed shifter and the 3 speed internal hub, these parts are now ready to be installed on the Bestrider Pump Pro 16 kids bike. 

As the frame does not come stock with an internal hub setup, we might encounter some complications for this project.

For a start, the frame has a horizontal dropout for its single speed drivetrain, so this enables chain tensioning by adjusting the rear hub position. I will also need this feature for the internal hub drivetrain.

Next, the rear frame width, or rear OLD (Over Locknut Distance) has to be able to accommodate the rear hub. The frame itself has an OLD of about 115 mm, which is considered narrow, but normal for single speed bikes.

The Nexus 3 speed internal hub SG-3R40 has a hub width of about 120 mm, if the roller brake is installed. Without the roller brake, the hub width would be narrower. I can add spacers on the hub axle, in order to match the OLD of the frame.

3 speed internal hub placed into the frame. This side with the sprocket cannot have spacers installed.

Without the roller brake, the hub width is narrower than the frame. Spacers can be added on this non-drive side to match the frame.

Added a 3 mm locknut to boost the hub width to match the frame width.

Yellow non-turn washer and axle nut with rounded cap on the non-drive side. Fits well.

On the drive side, a shorter nut with flange is used, as the bell crank needs to be attached to this nut.

Based on the manual, I need about 8 to 12.5 mm of axle protrusion from the end of the nut.

Axle protrusion is measured to be about 9 mm, so its within spec. This will vary depending on the thickness of the frame.

After inserting the push rod into the hole of the hub axle, it should protrude by about 14 mm. There are different push rod lengths available.

Protrusion is about 14 mm, so the push rod is of the correct length.

Stock single speed chain removed, to be swapped to a nicer chain that is more rust resistant and also lighter.

Dura-Ace HG901 11 speed chain, can be used on this drivetrain as the sprocket and chainring are of the thin tooth type. This is the leftover chain from combining two chains last time, on the Bike Friday Haul-A-Day cargo bike.

11 speed chain installed on the rear sprocket.

Chain length adjusted to give maximum rearward adjustment of the hub axle.

Here is the weight of the bell crank and push rod. This bell crank is of the nicer zinc die-cast type, SM-BC03.

Push rod installed in the hub axle, ready for the bell crank to be put on.

Trying out different cable routing along the frame. First I tried under the chain stay...

...above the chain stay...

Finally I decided to route the cable along the seat stay instead. 

Bell crank with the lower cover removed. The shifting cable will pull on the linkage inside, which pushes the push rod into the hub.

Shifting cable connected to the link.

Cable needs to be trimmed, so that it is short enough to swing around inside the bell crank and lower cover.

Bell crank installed successfully on the frame. No complications encountered.

Cable routes along the seat stay, and joins up with the rear brake cable to look neat.

Chain is tensioned by pulling the hub axle towards the rear. Tricky to get the chain tension just right, so that it is neither too loose nor too tight.

Bell crank and 3 speed internal hub installed!

Happy to have this 3 speed drivetrain installed on this kids bike. Definitely one of a kind.

This frame has a standard design, without any fancy dropouts or frame shapes, therefore the 3 speed drivetrain could be installed relatively easily. With this conversion complete, let's check out the full upgraded bike and the bike weight in the next post.

Saturday, May 21, 2022

Bestrider Pump Pro 16: Nexus Inter-3 Rear Hub

The next part of the upgrade for the Bestrider Pump Pro 16 is to install a 3 speed internal hub. I have previously used the Alfine 11 speed and also the Nexus 7 speed, as well as the Brompton wide ratio 3 speed hub.

Although I can build a wheel from scratch, having learnt it at Bike School Asia, I prefer to let others do it as I find it too troublesome. Not only it is a hassle to get the correct spoke lengths, I don't have the time and patience to do it well. Therefore, I bought a stock 16 inch 305 rear wheel with Nexus 3 speed  internal hub SG-3R40 from Taobao. It is actually the rear wheel of a Xiaomi QiCycle E-bike, but it so happens to be exactly what I needed for this upgrade.

Exactly what I needed, with black spokes and rims, to match the front wheel.

Uses the Shimano Nexus 3 speed internal hub, SG-3R40.

This rear wheel with internal hub is heavy, at 1242 grams.

Based on my estimation, a 18 teeth rear sprocket with a front 32T chain ring should give a good gear ratio. Shown here is also the dust cap and the snap ring.

Dust cap goes onto the hub first...

...before placing the sprocket on top and securing it with the snap ring.

Weight of rear wheel + sprocket is 1298 grams. Getting heavier now.

Finally, axle nuts plus the yellow non-turn washer is needed to secure this rear wheel onto the bike frame.

Single speed freewheel on the stock rear wheel.

Stock rear wheel + freewheel is 657 grams.

Add the axle bolts and chain tensioner, the stock rear wheel setup is 691 grams.

A fair comparison would be to compare the rear wheel system weight. In this case, the stock rear wheel system weighs 691 grams, while the new rear wheel system weighs 1298 + 37 = 1335 grams. The weight increase at the rear wheel is thus 644 grams.

To digress a bit: If I add a rear derailleur + cassette drivetrain instead, my estimate is that the rear derailleur would weigh around 250 grams, with the cassette another 250 grams. This ~500 gram increase would be a bit less than the 644 grams seen here from the 3 speed internal hub change.

This still excludes the additional weight of other components needed for the 3 speed drivetrain, such as the shifter and the bell crank, plus extra outer casing and shifter inner cable.

New wheel with 28 spokes on the left, stock wheel with 20 spokes on the right. I am happy to find a 3 speed rear wheel that has a matching appearance.

For now, the stock MTB tires will be used. Since I have to remove the tire and inner tube from the stock rear wheel and move them over to the new rear wheel, I took the chance to weigh them.

Stock MTB tire (52-305) is 314 grams. Actually not heavy considering the width and knobs.

Stock inner tube is 119 grams.

Stock tire installed on the new 3 speed rear wheel!

With the rear wheel ready, the next step is to assemble everything onto the bike and test it out. I have not installed a 3 speed internal hub system on a kids bike before, so there will be something new to learn and surely there will be some problems to solve.