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Old 10-25-2009, 08:02 PM   #1
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Default Opinions/Thoughts on potential touring car layout?

I was considering making a touring car with a electronic layout based off the Durango DEX410 layout to take to Snowbirds this year.There is a picture of how I'm thinking about laying it out below.I was wondering what are your guys' opinions and thoughts of this layout? Do you guys think this layout would perform well on a touring car? I'm afraid it might have a bit to much wieght on the front and not enough on the rear..but I wanted to get your guy's opinion before I went ahead with the project.
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Old 10-25-2009, 08:48 PM   #2
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You would most likely have to run in Modified, as ROAR rules say a kit has to be available to the public for 14 days before the event.

I think that with all the battery weight in the rear plus the shaft drive design, you would end up with a car that torque steered a lot. JMO.
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Old 10-25-2009, 10:16 PM   #3
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Hmm.. I have never heard of this rule..where can I find it? I briefly looked thru the ROAR rule book but couldn't find it.

Torque steer is a concept that is a concern of mine about this layout. I did some digging up on TC3 torque steer and what I found is that the Warpspeed Demon chassis conversion claimed to have no torque steer. They achieved this by putting the motor on the opposite side of the chassis as a stock Tc3 so it spun in towards the chassis instead out to the side of the chassis like the original tc3 does. This makes me think that I could cut down on torque steer by swapping the side that the motor is on in the pictures posted above.
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Old 10-25-2009, 10:37 PM   #4
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I used to run a modified foam tire TC3 on carpet waaaay back in the day when the TC3 first came out. It was an absolute handful on tight courses with all the point and shoot style of racing that indoor tracks typically exhibit. The torque steer was disasterous, and that was only with a 9-single. I can't imagine how bad it would be with a low turn brushless motor. On a lighter note, Snowbirds usually doesn't adhere to ROAR rules in a stringent manner, more over just as a template for certain guidelines. Your own creation may be legal for 17.5 with them, and thus, torque steer won't be bad at all.

First off, I applaud your desire to build and race your own design! So to get your efforts pointed in the right direction, start by considering designs that utilize the same components that will be found at the races you plan to attend. In this case Snowbirds, where most (if not all but the foreign racers) will be using Lipo batteries. Your saddle pack design could work, but the Lipo saddle packs are much lighter than NiMH saddle packs. It would be worth weighing the layout to determine the F/R balance in comparison to the more established chassis designs.

...and what if your center drive had some options like a differential?
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Old 10-25-2009, 10:56 PM   #5
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Where does the esc go?
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Old 10-25-2009, 11:12 PM   #6
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Off the top of my head it looks like the rear diff might have to be pretty high for the driveshaft to clear the batteries. Perhaps if you offset each pack by 1/2 cell you could lower the rear diff.

But for a NiMh car, it looks pretty cool, good luck. I like to see stuff like this work. Is it a bit long?

Torque steer (on accel or braking) is going to happen (although it may be minor) in this design, regardless of where the motor is. It (the motor) spins in the same plane as the car rolls. The car is going to roll a bit during acceleration and if you have any bump steer, you will get some torque steer.

A center diff would be sweet!

I would go for it! I mean if it's just a matter of having a carbon plate cut out, shucks yea, go for it. I've had carbon plates cut out from this guy ([email protected], http://eaglesviewaerial.com/index.html) and have been very pleased with the work. Probably around $100 for a 3mm chassis if you supply the CAD drawing.
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Old 10-26-2009, 02:50 AM   #7
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I reckon there will be too much weight over the front. Good for understeer unless you can get it 50/50 on the weight split.
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Old 10-26-2009, 03:20 AM   #8
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The weight in that design is over the REAR of the car - not the front.

With that layout there, you have ~420g of battery pack behind the spur, and ~300g of motor and electronics in front.

4wd buggies are built with a rearward weight bias, somewhere around 60/40. Touring cars are built close to 50/50. You will have a lot of mid-corner understeer with that weight distribution.

You're also running a higher CG due to the high spur and driveline (the Durango runs angled input shafts to clear the battery pack - hard to acheive without either a Durango or HPI Cyber 10B to base your design on).

Plus it is shaft drive - so torque steer will become an issue again.

All I can say is build it and try it! It might be a phenomenon. Or it might not...
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Old 10-26-2009, 03:39 AM   #9
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Quote:
Originally Posted by sosidge View Post
The weight in that design is over the REAR of the car - not the front.

With that layout there, you have ~420g of battery pack behind the spur, and ~300g of motor and electronics in front.

4wd buggies are built with a rearward weight bias, somewhere around 60/40. Touring cars are built close to 50/50. You will have a lot of mid-corner understeer with that weight distribution.

You're also running a higher CG due to the high spur and driveline (the Durango runs angled input shafts to clear the battery pack - hard to acheive without either a Durango or HPI Cyber 10B to base your design on).

Plus it is shaft drive - so torque steer will become an issue again.

All I can say is build it and try it! It might be a phenomenon. Or it might not...
Tourque steer is not an issue with brushless. Much lower rotating mass compared to brushed.

If the idea is to use lipo saddles then the weight distribution wouldn't be too bad, but, I also see problems with the shaft not clearing the batteries.
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Old 10-26-2009, 06:37 AM   #10
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If you used lipo saddles you could run one at the rear and one at the front. Move the motor to the rear and have it on opposing corner to motor (same with saddle packs on opposing corners). I imagine this would be close to 50/50 weight.

Also if you run the smallest possible rotor torque steer would be reduced. It would be best if the chassis was run in 10.5 or slower unless you are very happy with the handling prior to the event.

Of note the awesomatix uses shaft drive with different motor orintation. Might be worth looking at too as they claim to have no torque steer.
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Old 10-26-2009, 10:20 AM   #11
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Quote:
Originally Posted by Danny-b23 View Post
You would most likely have to run in Modified, as ROAR rules say a kit has to be available to the public for 14 days before the event.

.
humm is Snow Birds a Roar Sanctioned Event: or do they just use Roar Rules as a Guied line, If the they are just Using Roar Rules then it would be up the the Race director / organizer discretion.
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Old 10-26-2009, 10:42 AM   #12
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Why don't you turn the battery packs, so the driveline runs between the packs instead of over them. Like in a 4WD buggy design.

Where did you plan to run your ESC and Rx?
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Old 10-26-2009, 04:51 PM   #13
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Thank You for your guys’ thoughts.

I do plan on using a lipo saddle pack not Nimh. I also plan on using a brushless motor. I would like to try to find a racer to race it at the Snowbirds so no telling what motor/battery set-up they would use.

The Esc/RC will be mounted on the servo side and could be put anywhere along the chassis. I want to make the chassis slim as possible but I will keep in mind the Rx/Esc

I was looking and it would be possible to make and install a center diff. I’m not sure what advantage this would give though.

A major concern you guys are having in the center drive shafts clearing the batteries. I will be using a set up similar to the Durango’s. I’m going to be making custom bulkheads for the diffs so that I can mount the input shaft at an angle. I was thinking about just tilting the TC3 diff cases but this creates more problems than it solves. Here is a picture of a set-up that has used bulkheads on the tc3.I’m thinking that I will make it so I can put thin lexan enclosures on the bulkheads to seal them some from rocks ,gravel,sand, and such when I used it for parking lot racing. Who knows I might even be able to mold plastic around the bulkheads to keep stuff out of them using the heat gun and pop bottle idea.


For weight distribution it sounds and looks like about 50/50 is the standard for touring cars. What I’m finding is that it is possible to achieve close to 50/50 when using this layout with certain batteries. What is comes down to is that the center line is split right between the batteries and the motor, servo, esc, and receiver. The electronics I will be using minus the batteries end up to be around 300g. This means if I can find a lipo saddle that is close to 300g then I will be able to have close to 50/50. After checking most lipo batteries there are some that are very close to the 300g mark (SMC 4900 296g) but others are a little bit lighter. But usually within 40-50g of the 300 mark which can be compensated by with weight if needed. I don’t believe F/R distribution be a problem. Neither do I think Left to right will be problem either. I may have to move the batteries slightly offset on the motor side of the car but this will create an almost perfect left to right balance.

From what I'm hearing torque steer shouldn't be a huge problem. It may have a small affect on the car but I'm hoping with using a brushless motor, having it spin into the car,and using a stiff chassis I will be able to keep it to a minimum.

Please keep the thoughts and opinions coming.

Ethan
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Old 10-28-2009, 09:02 AM   #14
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Any further thoughts, opinions,comments, or concerns on this layout ? I believe I will go forward with this project but it would be nice to know if I need to incorporate or keep anything in mind when designing the car.

Thanks,
Ethan
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Old 10-28-2009, 11:43 AM   #15
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maby u should use a belt layout lots more room
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