Next Sunday (2nd October) sees us traveling up to Castle Combe for the Western Regional Heat. With a decent grid place under our belt from Merryfield, we will be using Castle Combe as a bit of a gamble, pushing our gearing a bit further. We will definatly go faster but there is a real risk of coming up short and draining the batteries too quickly. A lot more emphasis will be on the drivers to take smooth lines and efficiently avoid traffic but I am confident they can manage it.
For those of you who want to join us, Castle Combe is just off the M4 between Bath and Chippenham and is well signposted from Junction 17. The schedule for the day is as follows:
0730 - Teams arrive and sign on
0815 - Scrutineering opens
0900 - Team briefing 1
0930 to 1030 - Practice
1040 - Team briefing 2
1100 to 1230 - F24+ race
1300 to 1700 - F24 race
11730 - Prize giving
This is the last chance for teams to qualify so the field will be packed with cars desperate to put some great milages in, 57 cars have signed up for the race, including Megazord, the team that has finished one place ahead of us in both our heats this year. Also competing is Brian, the teams favourate car (after RLR1 of course!)
I'll see you there!
ReplyDeleteGot the F24+ race to try and gain some points to move us off the bottom of the table!
We have gone for the opposite, dropping the gearing down after the gamble at Merryfield so should be an interesting race.
Good luck in yours.
Hey Dan, what gearing are you running? at Merryfield we ran a lay shaft with two gear steps of 15:40 and 25:50 giving an overall ratio of 1:5.3. this is with 20" wheels. at Castlecombe we will swap out the 15 for a 16 giving us a total ratio of 4.4 but this will really be pushing our luck.
ReplyDeleteI'm liking the spread of false information, keeps everyone on their toes..! ;)
ReplyDeleteI'm sure that was it, im rubbish remembering numbers! Which bit did i get wrong?
ReplyDeletePrimary ratio is 40 / 15 = 2.67
ReplyDeleteSecondary ratio is 50 / 25 = 2
So final drive ratio is 2.67 x 2 = 5.34:1 (merryfield)
Need sleep...
So a 16 tooth pinion will give 5:1... :)
ReplyDelete5:1 of course it is. failure of arithmatic there im afraid!
ReplyDeleteSo the correct ratios are 5.3:1 at Merryfield, 5:1 at Castle Combe.
Well that went round the houses for a simple bit of maths!
Do I sense your trying to send me a false numbers hmm... no only joking.
ReplyDeleteThats a very low ratio, how do you get that speed with that? We use 20" as well and a ratio that low sees us going soooo slow! Gearing has always been something thats troubled me though.
We were on 3:2 at Merryfield, hence the batteries died, but moving down to 3.7 now with a 13 on the motor. We can get away with this higher ratio though as its F24+, but I cant get it right for F24!
The gears I use I've adapted from Goblin parts to give the belt drive, the main cog being a 48, no lay-shaft involved, linking nicely - I read on the forum that your now involved with a Goblin. When I'm back around November time or more likely December I can arrange a showing of the Goblin I work with if your interested?
Good luck for the weekend, I will be watching for a bit after my race.
Hi Dan,
ReplyDeleteI've been thinking about offering you guys some advice and since these projects are educational I'm happy to offer this...
Your gearing is far too high!
Take your merryfield figure of 3.2:1 on 20 inch wheels.
Your lap times would need to be in the 85 second range for your motor to be pulling a low enough current to finish the race. Your fastest lap was 114 seconds which according to my calculations would have required an average current of 46A, with an average motor speed of 1343 RPM. Any lap slower than this would have pulled more current and at a lower RPM - not good! I bet your motor was a bit warm...
RLR1 running a 5.3:1 ratio allowed its motor to spin around or above 2000 RPM most of the time, drawing a correspondingly low current.
You need to source a big old main cog, around 65 teeth to go with your 13 to hit a ratio of 5:1. The standard kit car ratio is 6:1 so ponder on that! All the calculations I've done are based on the motor performance graph - give it a proper look over...
Cheers, Ben
PS I'm on night shift with a new baby hence 1am posting!
Hi Ben
ReplyDeleteThanks for that.
Yeah Merryfield was too high but during testing it was achieving good speed with relatively low amps with a faulty motor so we went with that speed because we knew slower would not put us on course for enough miles to qualify. When consulting the motor performance graphs on Excel I was quite surprised how well the race went really as it did show a very high speed needed to get the low amps!
They were however no where near 46, they would be at about 15 for part of the race and max at the most 35 on the hill.
This is where I've been working on actual lap speeds rather than going by the graph.
Take the start of the season, running a gear hub with gear 3 (1:1) we ran 4.7:1 and were sooo far of the pace of everything else. As the races went on and Newquay arrived we had the ratio of about 3.4 single gear and pulling hardly any amps so moved it up slightly more for Merrfield, too much but never mind.
When I've put lower gears on, the car just does not have any pace to it hence the higher ratios.
Super Trug run about 3.3:1 which is what got me thinking this high end cant be all that bad, and when I heard the kit car runs at 6:1 I was in disbelief as we just could not keep up with them in such low gearing.
Believe me all you mentioned in your post I've been through many many times and just cant piece together the right ratio. I do wonder though if having a gear hub or layshaft plays some odd effect on things as the same ratio with a gear hub compared to straight single gear proved very different amps... I am most probably completely wrong here but its a thought.
Cheers
Dan
Many wise men of motor sport have said: "To finish first, first you must finish"
ReplyDeleteBest of luck with it Dan, I'm sure you'll crack it in the end.
By the way, I think Simple Trug is running 16 inch wheels...
Cheers,
Ben
Yeah I tell myself that all the time.
ReplyDeleteThanks, I've just got to keep going with it. Been doing this project long enough now to get most other things sorted, next year its gearing!
Yeah you are right they run 16", hadn't considered that. I'm doing a new Corporate car for next year so will try a lower gear and see what happens.
Meant to add before, congrats on the baby.
Cheers
Dan
Ben has pretty much said it all really. For a car running with 20s, 5:1 is pretty much the best you can do and even that is pushing it. It may be possable to get into the high 4.summit but the car would have to be superb and the driving excellent to pull it off.
ReplyDeleteOh, and if you want a decent sized sprocket in time for the final (like Ben said, you would probly want a 60T), try Lasermaster over United Downs. Find the right CAD drawing from www.solidcomponents.com and they might cut it our for you, you just need a file then to put a slight taper on the teeth to help them engage.
ReplyDeleteJust want to say thanks to you both for your help. I've taken your advice Ben and really gone over the graph in detail and I'm starting to get a grip more than I did to whats going on. I've used it to analyse my speed and amp data from Castle Combe and look at what could happen by altering the ratio down.
ReplyDeleteAnd Darren, thanks for that link its just what I needed. I've been trying to source some large sprockets but the prices are just ridiculous so I'll get my own cut. I've worked with laser master in the past and need some other bits cut so will get a big job sent to them ready for next season.
Well done at Castle Combe and see you at the final!
I've taken your advice and got a 60 tooth on order ready for the final, if it pays off I can but only send you my greatest thanks!
ReplyDelete