daleburr

I've had parts made by Fibre-Lyte in the past, their carbon is definitely the sexiest around! Once the prototype is tested to work out the bugs, the design will be going to them for a CF version.

The belt sizes are 68t, 92t and 97t, which I don't think are used by any RC cars (I found a big list here http://www.melbrc.org/vB/showpost.ph...52&postcount=1).

If the belts are causing an issue I can either sand them down to reduce their thickness, or look at getting Bando belts which is what most TCs use. I've found a supplier; they're about $12 per belt and will need cutting to width, so they're a last resort!

I run a Novak data logger on my cars so I can see RPM, speed, current draw, acceleration etc. So I'll be able to compare the new car with a standard TC6 to see if its any slower. I've been running the TC6 with shorty lipos to get a fair comparison.

Chrissy C

iTrader: (1)

Hi Dale,

I know of a 97t belt, a TOP Scythe one, PD-SDT015 - i got it from Demon thinking it would fit mine, but its way out, if you would like it let me know.

I'll check a few other obscure places i have found that stock a lot of drift car parts and belts.

That data logger sounds handy, have you noticed much difference (if any) with the standard TC6 and the shorty lipo?

daleburr

Thanks for letting me know about the TOP 97t belt; I'll see how the car goes and let you know. The rear belt (68t) is actually very flexible so I'm happy with that (the belts from BeltingOnline are lots of different makes, depending on the length, and some are stiffer than others).

So just a 92t flexible belt to find for the middle belt now.

The 4000mah shorty packs are no slower than a 5800mah full size pack, and had no more drop-off at the end of the run. I guess in blinky classes the voltage drop-off might cause a problem, but in boosted it's not significant.

alcyon

iTrader: (8)

Thats nice to know. i just bought 3 packs of 4000mah 60C shorty packs from gn-fusion from ebay, and will test them this weekend. the shorty packs helps to bring my Kawada Touring car weight down to 1400g. i am using the ORCA VX ESC and will be boosted.

daleburr

Top deck now done. Car feels a bit stiff so might make a thinner/narrower top deck, but will probably just run the car first since its just a prototype and the final one will be carbon. Nearly done :-)

Conrad

iTrader: (3)

Looking good Dale

Chrissy C

iTrader: (1)

Hi Dale, looks good.

What method are you using to secure the battery?

daleburr

There's going to be a U-shaped carbon lipo holder at each end of the shorty, to stop it moving around. Tape will then go at each end of the lipo, across the holders, to hold the pack in.

It's very tight on space though and the middle belt is in the way of the right-hand lipo holder (which I hadn't spotted in the design), so a bit more work may be needed in this area. By 'a bit more work', I mean the dremel will be coming out

daleburr

Well the weather in the UK finally improved for long enough to run the prototype car for the first time!

I ran the car after a race meeting on my local tarmac track (Bedworth in the UK www.bedworthrc.com). After a meeting is the ideal time for testing as the track is in a good stable condition, and I have a days laptimes to compare against.

I'm running 13.5 boosted, and my normal car is a fairly standard TC6 which is what I raced during the day for comparison.

The good
It works! I did two runs with the car and nothing fell off, jammed or destroyed itself.

It handles fantastic. On the first run the car had a bit too much understeer, so for second run I reduced the rear toe by 0.5deg. The car responded well to the change and felt stuck to the corners on the second run. It was very stable and consistent, doing consistent 15.7-15.9s laptimes, which compares well to my TC6 (ave lap of my best race that day was 15.8).

The bad
Holy shit the motor gets hot in this car. After 4 minutes the motor was at 120deg (yes, Celcius!!!). It's an X12 so it can take some heat, but my upper limit is 110deg for a 5 minute run so this is way too hot.

I think this is mostly due to lack of cooling. On a normal TC the motor hangs out the side, right in the airflow around the chassis. On this car it's in the centre of the car, and behind the Lipo, so gets very little airflow.

This is why I only did 2 runs as I didn't want to kill the motor, so it needs to be sorted before the car runs again. The action plan is:

1. Replace the GM ESC with a HW. I've now ran both and the HW runs the X12 motor 30deg cooler with the same performance, as it applies the boost much more efficiently. I've got an Xtreme stock on order as its about the same size as the GM75.
2. Fit more fans. That skinny 40mm fan I'm running shifts about 5cfm. There's loads of space around the motor, and the car is light on that side, so I'm going to fit a couple of 30mm fans instead which should shift about 11cfm total.
3. Lower the motor and make the chassis hole bigger. The motor is currently about 1.5mm above the underside of the chassis; I'd always intended to lower it to lower the CoG, and this might also help cooling.
4. Free the drivetrain up. I'm going to do some tests this week to see how much more current this car draws than the TC6 for the same motor/gearing etc, to see if the drivetrain is part of the problem.
5. Fit a cooling duct. This will be a lexan duct which sits in the airflow (where the motor would normally be) and pulls air onto the motor. Not sure I like this idea as it'll look messy and get damaged in a crash, so its at the bottom of the list.

Summary

Overall I'm very pleased with how the car goes and feels on track. If the handling had been off this might have been very difficult to fix, and involve lots of different chassis' with different cutouts/flex etc. As it is the handling is great, I just need to cool the motor down, which is a more tangible problem and can be measured.

dfiantii

iTrader: (18)

Doesn't Tamiya have something where a hole is cut into the carbon fiber below the motor and a duct of some kind is connected underneath to route air to the motor? That might be an option.

Conrad

iTrader: (3)

If your not too worried about the legality side of things just now then a hole in the front window and a smaller one in the rear works great for cooling the motor down. If you have so much space under the motor I would be tempted to increase the surface area of the motor and increase the cooling from the air passing under the car by fitting a sheet of aluminium in the hole under the motor. Screw it to the motor mount and drill alot of holes in the sheet to increase the surface area further. Glad to hear the car went well Dale.

KDagh1

Cool. Thanks for the project update. Good to hear.

alcyon

iTrader: (8)

i think with the carbon fibre chassis and top deck your car will only get better. on another note, perhaps you can mount a fan on top of the top deck to blow down on the motor. i think that will help a lot. i drive a 414 type of car and with the shorty packs i am able to free up a lot of space so i can actually put a 25mm fan between the space where the saddle pack was and the motor. With a 4000mah shorty pack and 10.5 motor that has been boosted quite a lot i still get 10mins of runtime which is amazing.

Chrissy C

iTrader: (1)

Sounds like a good maiden run Dale, well done mate.

Just to throw my hat in to the ring...

I think the motor cut out and lowering of the motor will solve most of the problems without having to add more fans etc.

Additionally what about trying another motor other than the X12 - these have a tendancy to run hot don't they? An option i've looked at is using the HPI Pro series motor, they look to be very reasonably priced (£55) and also have an inbuilt (optional) fan that is supposed to reduce temps nicely (by 15 or so degrees) with little to no impact on performace (Ben Cosgrove talks about it on Oople)

What thickness are you going to have the carbon chassis and top deck made out of? My chassis is 2.4mm, this coupled with a G10 top deck feels very stiff - tempted to have the next one made out of 2mm plain weave carbon...

Looking forward to the next update

daleburr

Thanks for all the positive feedback guys, some very useful suggestions there that I'll be trying over the coming weeks when the car runs again. A HW ESC and some Yeah Racing Tornado fans are on order which should solve most of the heat issues. I also think the current fan location means it's not doing much, as its blowing onto the plastic endbell rather than over the can as it would on my TC6. So I'm going to mount a 30mm Tornado fan behind the motor, as well as one by the endbell (although I'll try disconnecting the endbell one to see if it actually does anything).



Had a quick look at that; I can see a cooling duct for the 416 which is like you describe. Unfortunately it would involve raising the Lipos up to make room for a duct, not something I want to do.

I want the car has to stay legal, so the window cutouts are out. An under-motor heatsink sounds like a good idea. I don't normally like heatsinks as they add weight high-up and off to the side, but one under my motor would add weight in an ideal location.

I want to keep the weight low down, but there's room for a fan behind the motor. I've just ordered two Yeah Racing Tornado fans which seem to be the best available. Two of those should do the job I hope!

Hopefully! I kept the motor cutout small at first for stiffness, but the chassis is actually very stiff, so a bigger cutout won't hurt.

They do run hotter than other motors, but they are also safe to be run hotter, so the end result is about the same. With my Hobbywing ESC in the TC6 the X12 only runs at 70deg, so they can be run cool with the right setup.

It will be 2.0mm from Fibrelyte. Their carbon is quite stiff so it shouldn't need to be any thicker, and a thinner chassis lowers the CoG of everything mounted to it.