Motor

[M 800STD 586]

My 4s speed challenge motor arrived today...

 

[Wooders28 4718]

Wow, please tell me that's not for the speed run on here! 😯

[M 800STD 586]

lol, 85cm long of pure goodness.  There may be a listing in the non-T cars.  ; ) 

Next, sort out ESC.

[Peter_B 997]

So that's how they're going to get the new Space Shuttle into orbit!

 

[M 800STD 586]

I really can't wait to set this car up, but I know It's going take a while.  I want to be ready for August - I doubt I'll make it.

It tickled me when motor manufacturer gave warning with this motor.

Calculations are indicating it should crack current 4s record.

[Wooders28 4718]

23 minutes ago, M 800STD said:

Calculations are indicating it should crack current 4s record.

Out of interest, what is the current record?

[M 800STD 586]

163.9 mph through speed traps, not GPS.

If you go to Post, "Caps & Fets" in this section there's a vid of the run.

[Wooders28 4718]

21 hours ago, M 800STD said:

163.9 mph through speed traps, not GPS.

If you go to Post, "Caps & Fets" in this section there's a vid of the run.

Wow!! 😮

[M 800STD 586]

Slowly gathering the final parts for project.

ESC purchased today, extra specs included terminal rings, motor/battery, for 4 AWG.

Just a comparison, 1/8 challenge car vs 1/10 T.

[Jonathon Gillham 4605]

1 hour ago, M 800STD said:

Slowly gathering the final parts for project.

ESC purchased today, extra specs included terminal rings, motor/battery, for 4 AWG.

Just a comparison, 1/8 challenge car vs 1/10 T.

I was hoping that motor was going in a 10th or 12th scale pan car...

[M 800STD 586]

1/12 scale too small for speed challenge, will just keep getting unsettled during run.

1/10 was what I was going to do, but then this car caught my attention.   1/8 scale 4WD Pan car, which should be more stable.

Considering the size of motor and my primary aim on 4s, I needed a controller to take care of this.  MGM was the answer.  Unfortunately it's a little big and require Rx batts.  The 1/8 scale car gave me space for components, unlike a 1/10 chassis.

Later, I'll probably use the same car for 808 challenge, 8s.

 

 

 

[Wooders28 4718]

13 hours ago, M 800STD said:

1/10 was what I was going to do

Please tell me it was a tamiya buggy chassis, A Hornet! Just for giggles.....

[M 800STD 586]

Sorry Wooders, no.  The power of the system would of just tore it to pieces.   

I originally purchased a 5T motor and 280A ESC set-up for my Yokomo, just to update the car and make it a little bit quicker, with intentions of entering it in non-T category.

Now all the electrics are going on a F103, to compete in T class.

I have had thoughts of putting it all in an Optima, maybe at a later date.

[M 800STD 586]

To ensure I was on the right track, a Rossa Forum member, very kindly, did some calculations for me:

 

Ok so I have a few minutes to try and outline the calcs I did for the Buri.

The Buri weighs in about 3.65kg and you will want to accelerate it as fast as possible without losing grip. So what sort of torque figures can we put through the wheels before they slip. I put the car on the bench and attached a line from the back of the car over a pulley and put a scale on the line and pulled the car to see at what weight the car would slip. Not very scientific but you get the idea.

It turns out you can get about 5KG of traction. This is very rough but if you look at an acceleration of between 1.2 and 1.8G you are in the ball park. So 5kg on a wheel that is 75mm diameter is 184 N/cm. The gearing for the Buri on my car is 19/53 (I'll check later) so the torque output required at the motor is 66 N/cm. This% efficiency so lets look at 70%, might be less, that equals 94 N/cm

If you look at the chart from Lehner the 2250/3 will put out 93 N/cm. bang on!

Obviously we haven’t considered drag yet so lets do that. We need some input figures first

•   Target Speed   170mph
•   Weight      3.65kg
•   Max thrust    5kg
•   Body      270mm x 100mm
•   Cd      0.3

I have a spreadsheet that will work stuff out and the car will reach 170mph in 7.6 seconds and cover 332 metres. The calcs also show that the car will top out at 214mph.

If you add any sort of downforce to the car it will increase the drag considerably so you will need a decent body. I have lowered mine 15mm so lets see what difference that makes to the calcs

171mph in 7.2 seconds and max 226mph

And if we increase the Cd to 0.36 due to downforce we get

170mph in 8.2 seconds and max 198mph

The problem we have is the wheels slipping due to no suspension on the Buri. The wheels will slip as the car lifts over the bumps. You will need a really flat surface to get up to speed with no wheel spin.

I wanted to install a G force meter on the car and you can then measure unloading of the wheels and see the effect of suspension. I might try this at llanbedr

[Wooders28 4718]

Have you decided on a body yet or are you designing one? 

Can't wait to see it run!

 

[M 800STD 586]

It looks promising, but in reality with no suspension, we'll see.

Yes , I'll be using HPI Proceed shell for now, with modified rear wing, as there's too much.  Basically the same as T Toyota GT-One TS020.

I'm sure there'll be a entry from me.  : ) 

[M 800STD 586]

My ESC tuned up today, which got me pretty excited and worried.  Why worried, well after unboxing and seeing the size of it.  I was told by a Rossa member that it would not fit my chosen chassis, but thought I'll make it fit.

 

[Wooders28 4718]

Wow, just wow!

17s lipo and 400 amp, that's a serious bit of kit.

 

[GregM 1109]

37 minutes ago, Wooders28 said:

Wow, just wow!

17s lipo and 400 amp, that's a serious bit of kit.

 

Just imagine what would happen if you attach a Conrad 240826 to it.

[M 800STD 586]

@Wooders28

She's quite a lump.  You gotta love the conductor connectors.

Dry fit has already shown problems, the ESC does not fit within shell cockpit.

@GregM

It would be like Superman flying around the world, righting all that is wrong.

About a month ago, in another thread, I made a comment that I was surprised at the Vmax difference between 4 and 8s.  Reason was given by members, that this was due to motor Kv values.  This may have an influence but I do not believe this is the reason.

I believe the lack of high powered ESCs is the reason.  There's a multitude of chassis, motors and batteries but not ESCs.  Right now I can only think of 5 high powered ESC manufacturers and that's including Castle and one of the manufacturers are not fabricating anymore, just repairing.

Anyway, that's my thoughts on it.

 

[Kingfisher 1171]

Can you tow the ESC on a trailer behind the car? 

[Wooders28 4718]

10 hours ago, M 800STD said:

She's quite a lump.  You gotta love the conductor connectors.

Those connectors look the same as the 415v contactors in the switch rooms in work! 😮

10 hours ago, M 800STD said:She's quite a lump.  You gotta love the conductor connectors.

 

Dry fit has already shown problems, the ESC does not fit within shell cockpit.

One solution would be to split the esc into 2 components, it looks like the top half is the processor and the bottom the power handling components. 

With the price of those things, you'd have to be really confident though!! 😕

Another, would be to re-design/modify the body to fit, I've not finished (all the bits, not assembled yet!) my vac former, but @yogi-bear is having good results with his.

[M 800STD 586]

@Kingfisher

That would mean building a trailer, I'm incredibly lazy.

@Wooders28

As a last resort I will alter profile of shell.

I've already got the fans off and will remove heat sink to machine down.  I'm also looking into lower profile fans.  One final thing I can do is remove the chassis battery plate, which should give me a couple more mm.  This also will give the chassis more flex - better traction.

So now with the ESC so close to shell, I will have to fabricate roll over bar.

 

 

[M 800STD 586]

Today just been doing some research into fans and came across this site.  Very comprehensive list with CFM values, instead of some bloke holding a fan over scales at different heights.

https://www.digikey.com/

So much useful stuff here.

[M 800STD 586]

A little progress report.  I rearranged the layout and it looks like I'll be able to fit the ESC without modifications.  The original plan was to use saddle pack arrangement, but found a manufacturer that would make me packs to my spec for a fair price.  The ESC has to be mounted with silent blocks, which take up valuable space, so it is still touch and go whether it will all fit in.  What else, blank PCB for x8 caps ordered, just need to order the caps from RS - found some low Ripple value components.  I'm that lazy I purchased x2 roll bar sets, one to be placed at the front and one at the back of the ESC.

Another area I've been looking at was the steering assembly.  This original comprised of laydown servo, single post servo saver/steering column.  My version, modified top plate to mount inverted servo with servo saver horn.

There is one other area I'm thinking about, the rear pod.  As the car has no suspension, I was thinking of having it mounted on pivot plate, as the front is - giving far more chassis articulation.  Not sure at the moment.  I'll have to get the car built up more before a decision is made.  Initial testing has shown that the Buri does require a lot of dialling in for speed runs.