Going down a hill quickly

[Mark (smokey mow)]

12 minutes ago, Scott Young (Captain Colonial) - Club Secretary said:

Looks like @Mark (smokey mow) did well compared to the other entrants (starts at 23 seconds in):

 

 

thanks Scott, yes I survived 😀 absolutely shattered now after a long day so will update tomorrow but we made it to the finish, all in one piece and with no crashes or stoppages.

[Mark (smokey mow)]

Now I’ve had a chance to recover I’ve more time to type a full round up of the day.

 

It was an early start on Colchester High Street; as a penalty for getting my entry in so early we were were given the earliest arrival time of 8am.  Next year I’ll put my entry in last minute so we get the 10:00 drop off time.

 

 

Scrutineering went without a hitch and we were given our pass sticker to display on the car. My OCD wasn’t best pleased that it was slightly off centre on the nose cone.

 

After this we had a good couple of hours to waste till the 11am start time so we went off to admire our competition and pick up some tips from the pros.

 

 

There was a good mix of styles and designs. The most popular chassis were based on karts and quad bikes whilst a few others used tricycles. The rest like me built their own chassis.

 

 

 

 

There was plenty of admiring glances from the crowd and plenty of children had a photo behind the wheel, after swapping notes with the seasoned pros I realised that my wider wheels may be a disadvantage on such a flat course where all the speed comes from the initial push rather than the gradient of the hill.

 

Not to be deterred we lined up in our number 4 spot (although 3 on the road as one didn’t turn up) ready for our first run.

 

The start ramp was a monster and quite steep too, the two karts ahead of us bottomed out on the transition as they were pushed up the ramp, hopefully they made it off ok. 

 

No such issues for us, the short wheelbase and the minimal overhang front and back meant that nothing caught on the way over the top. For the first run my instructions to my pushing team of Ian, Paris and Dawn were basic and clear: a good firm push but not too hard as this was the first time I’d driven the kart at any pace so I want to get a feel for it.

 

From the off it felt steady as we rolled down the ramp onto the tarmac. I steered it with ease through the kart wash, getting a good soaking of soapy bubbles on the way.  

 

 

Up and over the speed bump I could feel it was loosing a bit of speed at this point as the road flattened and I rolled towards the barrage of super-soakers. Under the finish arch and I was just happy to get a clear run and record a time.

 

As I sat near the finish the others started to roll in behind me in various states of undress and a good few needing to be pushed there.

 

I’ve no idea what my time or position was but I was guessing we were somewhere in the top half.

 

A time if anything less than 30seconds was considered very good, 30-60 was the average range and plenty failed to break one minute.

 

The top two sports were taken by the sister cars of ADP classic racing and Techniq. For those who were thinking that my kart was over engineered these were were in a league of their own in terms of chassis and design. Both cars had inboard suspension on pushrods and full carbon fibre bodywork. Unsurprisingly they ran the course in 23 seconds. 

 

We had a good long wait till our next run so a chance to get my race weight up with some lunch.

 

Come the end of lunch we lined up again for run 2. Feeling more confident about the handling my pushers gave it all and everything they had. With the timing beam at the bottom of the ramp we lined up right at the back to get the biggest run up possible.  As I launched off, Ian hit the deck as Paris and Dawn sprinted down the track behind me.

 

This run felt considerably faster as I went through and over the obstacles. I got well and truly covered by the kart wash to the point I could see out the goggles and then soaked by the super soakers. Crossing the line I had a short interview with BBC Essex who informed me of my finishing time of 30seconds. 

 

 

Time to relax and watch the other runners come in.

 

 

 

[Geoffrey Carter (Buttercup)]

I have really enjoyed following all this.

[Nic Chase (NICO) - Shropshire & Mid-Wales AO]

Well done Mark. Thanks for sharing all of this. It’s been refreshing to follow a different build thread. 
I can smell upgrades  😂
Keep us posted on your next outing. 

[stephenh]

Well done Mark. Did you have the tyres pumped up to their maximum safe limit? It makes a big difference to your rolling resistance.

[Mark (smokey mow)]

Final glory fell to the team from ADP classic racing with the sister Tecniq car a fraction of a second behind them.

 

Third place fell to the BBC Essex team who were in a car loaned to them by one of the countries most seasoned racers and our scruitineer for the day.

 

The next few spaces after that were occupied by karts with two things in common, firstly narrow wheels and secondly no suspension.

 

The first I already knew when I built the kart and realised I was taking a risk, but on the flat course the narrow and also critically lighter wheels reigned supreme as they had the lowest rolling resistance and could be accelerated faster by their team of pushers.

 

The second point was less obvious to me but looking back the photos and videos I could see that I was loosing momentum at the bottom of the ramp and also on the speed bump because of the suspension compression. Despite the firmness of my suspension I noticed that I was getting more compression than I’d expected which was causing it to reach a point where the wheels were toeing in quite a lot. Clearly I need to raise the steering rack slightly and possibly change to an even stiffer spring to improve the geometry.

 

You can see the issues with compression and toe here.

 

 

[Mark (smokey mow)]

31 minutes ago, Nic Chase (NICO) - Shropshire & Mid-Wales AO said:

Well done Mark. Thanks for sharing all of this. It’s been refreshing to follow a different build thread. 
I can smell upgrades  😂
Keep us posted on your next outing. 

They’ll be more to come in the future Nic.  

[Mark (smokey mow)]

33 minutes ago, stephenh said:

Well done Mark. Did you have the tyres pumped up to their maximum safe limit? It makes a big difference to your rolling resistance.

Thanks Stephen, the tyres were pumped up to 30 but that wasn’t the issue. Much like a flywheel heavy wheels and tyres are difficult to accelerate, and putting it simply, those with bmx wheels could accelerate off the ramp faster than I could. 

 

what did help me though was that once rolling, the inertia and kinetic energy would keep me going for longer.

[mikef]

Well done Mark.  Looks to be great fun.

[Mark (smokey mow)]

17 minutes ago, mikef said:

Well done Mark.  Looks to be great fun.

I’d recommend anyone to give it a go.

 

it’s good cheep fun. Next year we’re planning to dress up too.

[djm]

Great write up Mark and we'll done for taking up the challenge.

Do you plan on entering any more events now that you have got the bug? Maybe tracks that suit your design better, I was amazed how many events there are around the country.

[Mark (smokey mow)]

4 minutes ago, djm said:

Great write up Mark and we'll done for taking up the challenge.

Do you plan on entering any more events now that you have got the bug? Maybe tracks that suit your design better, I was amazed how many events there are around the country.

we’re talking about doing Gt Dunmow which I posted about a few months back.

 

it’s a much steeper track with some big jumps and hard obstacles so it’ll suit a robustly built kart much better.
 

Certainly the plan is to do a few more events and Colchester again next year.

 

I’ll have a think for a while now but need to decide whether to upgrade this kart or learn from this race and build something even better.

 

 

[Dan Ingram]

Well done! It's been very enjoyable following along with this. 

 

With regards to tyre pressures, a lot of research in the cycling world has shown that pumping your tyres up to maximum pressure doesn't equal the least rolling resistance. 

 

We used to run 100+ psi, and now I run 65 ish psi. Might be worth looking into. Not sure how it translates to moped tyres, though.

 

 

[Mark (smokey mow)]

21 minutes ago, Dan Ingram said:

Well done! It's been very enjoyable following along with this. 

 

With regards to tyre pressures, a lot of research in the cycling world has shown that pumping your tyres up to maximum pressure doesn't equal the least rolling resistance. 

 

We used to run 100+ psi, and now I run 65 ish psi. Might be worth looking into. Not sure how it translates to moped tyres, though.

 

 

A pair of wheels is designed for a 90kg moped and rider so realistically my kart should be good for 400kg.

 

much like a Westfield I could probably run them with virtually no pressure and they’d still hold the same shape.

 

 

 

[Naranja_Al]

I’ve enjoyed stumbling across this post this morning. What a fantastic quality build.

 

Well done @Mark (smokey mow)