DMAX Tech Blog

Building the bespoke DMAX karts.

Putting together one of our high performance 2-stroke DMAX karts is very much like making love to a beautiful woman or actually like putting together a large jigsaw puzzle. A team of 3 engineers takes 90 minutes to build just one kart from scratch. The chassis arrives from the factory part built which is handy as otherwise it would take a week for each kart! The engine comes in two boxes containing roughly 1000 pieces.

One engineer takes care of dressing the engine while the other two work on the front of the chassis and the back. Each of the 3 radiator mounting brackets is handmade and a few of the standard parts need
modifying to fit this engine on to the chassis.

Although Birel's build quality is excellent, the steering geometry is laser checked as a matter of course and adjusted if necessary. Once the engine is fully assembled, the wiring loom and fuel pipe is added to the
kart and tie-wrapped in place neatly. The engine still can't go on the chassis yet as the chain guard uprights and the sprocket and protectors must first be loosely fitted. Meanwhile, the radiator, Nassau panel, front bumper and L/H side pod are all fitted along with the battery box and exhaust mount.

It's very important to get everything in the right order as it's easy to forget one small detail and have to remove a load of stuff because you forgot to put the 'nodule sprocket' on the 'whatsitsname' before you
tightened down the 'thingamyjig.' The first kart took about 4 hours to build and the best time was 56
minutes, but the average is around 90 minutes.

Now the engine can go on and the throttle cable fitted and adjusted along with the chain and guard. The rear bumper and R/H side pod and we're on the home straight. Side wrap pieces are attached with liberal
use of copperslip. Axle covers are modified with the use of a jigsaw and rubber grommets fitted. (Those are tricky little suckers.) The exhaust goes on last and it's more or less ready to run-in.

Running the engines in is one of the most boring and frustrating jobs known to man. You've just spent days building these fabulous machines and all you want to do is give them what for, but no, a strict procedure must be adhered to. 3 sessions of 10 minutes slowly building up the speed with a richer oil/fuel mix than normal is what the doctor ordered. Finally in the last session you can really let it all hang out and push the karts hard.

After running them in, they are fully spanner checked again, number plates fitted and stacked in the container ready for you - our customers - to race them.

So before you drive one next, instead of stacking it hard into turn 6, just spare a thought for us engineers who quite literally expend blood, sweat and tears to bring you the fastest arrive and drive karts in the country.

 

 

Keeping the DMAX karts running well is pretty much a full time effort and there's lots of things that go on behind the scenes that the competitors don't know about, so I thought I'd put pen to paper - or fingers to keyboard actually - to bring you all the latest developments.

As you know, toward the end of last year we increased the power of the DMAX karts which gave an extra punch of mid range power. This was achieved by increasing the size of the exhaust restrictor and changing the size of the main jet. That was easy really. More complicated though is the one area of the engine that has always given me problems: the clutch. Early in 2009, Rotax brought out a new clutch to replace the effective but relatively unreliable original design. This much simpler, more robust clutch was perfect for our karts but as you can imagine, changing 30 odd clutches is a time consuming and costly exercise. The new clutch also demanded a new set of steel balance gears to replace the rather flimsy nylon gears that I used to change every 50 hours as a matter of course. I took the decision to replace the balance gears before the clutches as it made sense to allow time for any problems with the new design to be fixed. I'm glad I did wait as there were a few problems with the clutch that took 12 months for Rotax to fix. Now I have 30 new clutch kits winging their way to MK to be fitted over the next few days. There's no difference in performance, only to reliability, so I can't wait to fit them and more or less forget them for the time being. It's horrible watching you guys fly round the track and hearing the tell-tale tinkle sound from a clutch on its way out and it's obviously frustrating for a competitor who is the victim of a failed part.

You learn a lot while working on the karts and while it's easy for me to bang round the track during the week testing stuff, it's not until you get customers on the karts that you really begin to find problems that you never knew existed. For example, I did hours and hours of testing the prototype kart nearly 2 years ago and never once did I bend a sprocket or snap a chain. The very first time any customers drove the karts we bent 3 sprockets and wrecked 2 chains. Fitting sprocket protectors pretty much cured that but gave a different problem when we took them to Lydd a couple of months ago. The big gravel trap on the last corner claimed many drivers. It also claimed many sprockets and chains as the sprocket protectors trapped the pea gravel inside!

Changing the gravel to a moist bark mulch type material fixed that problem whilst also giving the effective speed reduction that a gravel trap should.

A lot of the little changes we make go completely unnoticed and whilst a lot of our development is reactive, some of it is also trying to stay ahead of the curve and they'll be updates soon on brakes, tyres and more interesting stuff as the season progresses. Stay tuned....

 

Richard Brunning, Group Technical Manager

HND in Mechanical and Production Engineering
22 years of racing experience winning club and national titles in karts and cars
8 years as a rally navigator
4 years spent in the USA, racing cars and karts and also engineering with Formula Mazda team
3 years with the Zip Young Guns team
Numerous self built race and rally car projects