Bikeology.net

So over the last couple of days I built a new sound system, this time it was a small one designed to go on the back of a Pashley upright trike. It needed to be small, lightweight, very efficient and as loud as can be. I opted for 8″ versions of the speakers I use for Beatrix’s top box, they handle outdoors quite well, are lightweight and go bloody loud off sod all power with 95db efficiency off 1watt. It handles 200w rms and is powered off a small 12v sealed deep cycle battery. The amp is a Vibe VP2 amp, noted for it’s efficiency and built in crossovers and protection systems, so the speakers wouldn’t get damaged if it was ragged. It’s also trimode capable so at some point I could make an add-on unit with more power and a sub.

Anyways here are some build photos.

The bike, a Pashley trike brought off eBay for around £300.

All the bits

Two of the panels needed to be a trimmed an extra 1cm due to an error in calculation by moi, and not having a proper workshop meant improvising. Ghetto blud!

The office vacuum cleaner serving as a dust extraction unit 🙂

This is why I get told off at work, the dust goes everywhere!

Perfectly trimmed. Yeah baby!

Before everything is glued, I checked to see if it all fits together ok. The wood is 18mm Marine Ply, sadly B&Q didn’t have 15mm in stock.

The next thing to do was to cut out the holes for the speakers. I used a company to draw the wholes on the faces before realising that the takeaway container lid from the local Lebanese place was exactly the right diameter. I have shakey hands at the best of times so routing the holes freestyle was out of the question, so I nicked a remnant of Beatrix V1 and made myself a circle jig to fit the router.

Fitted and ready to go, I was a bit nervous at this point!

Wooo it works! Bloody loud though! Thankfully I had eye and ear protection, and trust me it was needed!

Just look at that perfect, smooth circle!

The perfect fit and a beautiful speaker, almost brought a tear to my eye.

Both speakers done 🙂 Loverly job. Time for a cuppa

The next step was to find a way to fit the base to the trike, thankfully I already had the right sized bolts and a handy strip of metal with holes! How lucky is that?!

The gluing process starts, those blue clamps were invented by God himself, what marvelous things!

Time for a little snack as the glue takes hold, mmmm shandy and chedder 🙂

Measure and think of ways to secure the battery.

The top is glued on.

Battery is secured and amp goes on. The amp, tweeter and fuses will live outside, covered by a polycarb sheet. This system won’t be used much when it’s wet.

Cabling and external struts go on.

A quick test, yup it works! I had to put a bit of extra acoustic wadding inside to get the best sound.

And there we go, it fits on nicely, works very well and the bike handles brilliantly thanks to some careful thought on placement and cog.

Afterburners FTW!

Lastly, time to set the gains using my trustly oscilloscope and measure the voltage for drops and set the amp not to push it too much.

And there you have it 🙂

Run time is about 2hours at the volume needed, and fecking loud it’s About an hour before the voltage drops to 11.8, the amp runs down to 11v stable.

The only things left to do is get a piece of clear polycarb and bolt it on the top and to paint the whole thing, I’m thinking black or Royal Blue to match the trike.