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Old 05-10-2009, 01:41 PM   #241
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It's very good to have access to a CNC mill but It's difficult to squeeze these little side jobs in when the machine and operator is usually very busy. I've been waiting about a month to get the chassis cut. It's finally getting done but I think I may need to outsource a few other parts just to get them done sooner. It's going to cost $$ though.
In college, I had access to conventional mills/lathes, CNC, water jet, lasers. Have you considered finding a shop with a waterjet? I was part of Formula SAE (http://www.niumotorsports.com/formul...tures_2008.htm) while in school and the majority of the things we made for the race car was made on the waterjet. There is practically no setup time since all you do is throw the material down in the cutting bed and clamp or weigh it down. Simple parts like chassis plates can be cut out in less than 5 mins depending on material thickness. Cut quality isnt as great as a machined part but if you're just building prototypes, it shouldn't matter. Cutting screw holes are ok on the waterjet, but for the most part we marked hole locations with the waterjet and used a drill press to drill and countersink afterwards.
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Old 05-10-2009, 04:16 PM   #242
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Here's the one I built. Don
Frankenstein Astro Flight motor and an eight pack.
Nice... I bet that thing flies!
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Old 05-10-2009, 04:17 PM   #243
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I have a 1/8 pan car with a ball diff. I was referring to my Evolva or any 1/8 4WD road car. I know on another forum(RC Monster) a gentleman by the name of Serum converted a Serpent and equipped it with a rear ball diff and it worked fine. Why would it not turn with a rear ball diff? With a solid rear end you're not turning as much as you're sliding. Don

The point of a spool rear end is maximum grip for forward bite. We rotate the car by lifting (more correctly reducing contact - not actually lifting off the ground) the inside rear tire when turning, thus, creating a controlled three point contact patch. Very effective and efficient once you grasp the concept. Read up on Go Kart racing - we use the exact same tuning techniques. I assure you, if a diff were faster, we would use it.
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Old 05-10-2009, 04:20 PM   #244
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In college, I had access to conventional mills/lathes, CNC, water jet, lasers. Have you considered finding a shop with a waterjet? I was part of Formula SAE (http://www.niumotorsports.com/formul...tures_2008.htm) while in school and the majority of the things we made for the race car was made on the waterjet. There is practically no setup time since all you do is throw the material down in the cutting bed and clamp or weigh it down. Simple parts like chassis plates can be cut out in less than 5 mins depending on material thickness. Cut quality isnt as great as a machined part but if you're just building prototypes, it shouldn't matter. Cutting screw holes are ok on the waterjet, but for the most part we marked hole locations with the waterjet and used a drill press to drill and countersink afterwards.
The Stig told me to put a couple wings on it and a little more tire and let it rock. I had a shifter cart and it only had a 125 rotary. That looks bad ass with a rice burner I-4 in it. Way cool!
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Old 05-10-2009, 05:09 PM   #245
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It does! I hit a rock in the parking lot once and the front end came up and it was airborn! Don
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Old 05-10-2009, 06:07 PM   #246
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Old 05-10-2009, 06:34 PM   #247
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The Stig told me to put a couple wings on it and a little more tire and let it rock. I had a shifter cart and it only had a 125 rotary. That looks bad ass with a rice burner I-4 in it. Way cool!
600cc crotchrocket engine, power limited due to a 20mm air restrictor right after the throttle body. Some teams develop turbo systems. The competition is both static and dynamic. We were judged on engineering design aspects along with costs. Dynamic events were autocross type courses. There are only a few teams that choose to design and implement wings. Those teams usually use thier cars at the SCCA Nationals where they go alot faster. The course is usually designed to limit speeds to 70-80mph. Our team usually chose to leave areo development out and concentrate on other areas. More tire is usually better but it also adds wheel and tire weight. The car only weights a bit over 400lbs wet, without driver. Every year requires a new car to be built. If I only had the resources to buy last year's chassis and drop in a 1000cc unrestricted engine.............
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Old 05-10-2009, 07:33 PM   #248
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600cc crotchrocket engine, power limited due to a 20mm air restrictor right after the throttle body. Some teams develop turbo systems. The competition is both static and dynamic. We were judged on engineering design aspects along with costs. Dynamic events were autocross type courses. There are only a few teams that choose to design and implement wings. Those teams usually use thier cars at the SCCA Nationals where they go alot faster. The course is usually designed to limit speeds to 70-80mph. Our team usually chose to leave areo development out and concentrate on other areas. More tire is usually better but it also adds wheel and tire weight. The car only weights a bit over 400lbs wet, without driver. Every year requires a new car to be built. If I only had the resources to buy last year's chassis and drop in a 1000cc unrestricted engine.............
Like the Stig said ...
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Old 05-11-2009, 06:07 AM   #249
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Hi Rich, thanks for the reply. I wonder if with the instant torque of an electric a ball diff might do just as well? I watched Yodog's video of 1/8 practice and it seemed as though I saw a lot of cars sliding around. Don
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Old 05-11-2009, 09:51 AM   #250
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I was looking into the DXF cars and came across this on thier website:

http://www.dxf-competition.com/pdf/dxf_9550_301107.pdf

Its a 3d model that you can hide/show parts just like any other 3d modeling software (Solidworks/ProE).

I dissected the model and it shows that theres a rear gear diff. The only thing that confuses me is there is no suspension. Do these 2wd pancars rely just on chassis flex as thier suspension? I know on electric pancars theres usually a movable pod in the rear and some sort of simple suspension in the front hubs but it doesnt seem thats the case with the DXF.
You are correct. It's all chassis flex and you may have noticed that it's adjustable by changing the mounting points of the upper plate.
A 2wd car must have a diff or else the car won't turn very well vs a 4wd car that can force turning by the use of a oneway on the front wheels and the small amount of overdrive built into the drive system. The solid rear axle on a 4wd car creates tremendous forward bite thus pulling out of a corner aggressively and accelerating quicker than with a diff.
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Old 05-11-2009, 10:16 AM   #251
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Hi Rich, thanks for the reply. I wonder if with the instant torque of an electric a ball diff might do just as well? I watched Yodog's video of 1/8 practice and it seemed as though I saw a lot of cars sliding around. Don
1/8th car sliding around has to do with mulitple reason, but most likley, it is the track condiiton that not up to the best condition....with the rear floating butterfly suspenion alot with the 'TABLE TOP" type lola body...rear downforce should not be a problem when running with rear spool.

Like other mentioned...if 4WD running with DIFF is better...you won't see the spool on all the 1/8th right now. We are talking about the fastest class with the most expensive stuff to put in...only the BEST will be in the chassis.

Looking forward to see that 6S conversion on track running along side with the nitro....
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Old 05-11-2009, 10:20 AM   #252
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Hi Rich, thanks for the reply. I wonder if with the instant torque of an electric a ball diff might do just as well? I watched Yodog's video of 1/8 practice and it seemed as though I saw a lot of cars sliding around. Don
It was early in the day, during practice so the bite on the track had not come up yet. It kinda shows how much easier the electric was to drive on a dusty track in comparison to the nitro cars. A smoother torque curve and not having a clutch to snap the drivetrain makes the electric cars a breeze to drive.

One more comment regarding the use of a diff on an 1/8th scale. These cars have been around and in development for decades. They have been driven and tuned by the best of the best. These guys are some of the most innovative racer/developers in the world so their only concern is to be faster and smarter than their competition. You can rest assured that they have seen and done it all. Some of the things they've tried would make the hair on the back of you neck stand up. I've been around this hobby for close to 20 years and the stories if heard...

Well simply put as Rich Browne said, "if it made the car any faster, we would be using it".
Typically, we only drive these cars on a prepared racing surface with plenty of traction. They simply won't drive worth s#*t on a dusty playground or parking lot. That's the only place the diff would be of help but we don't race there. So the current setup (solid rear and front oneway) is the way to go.

I hope this clears things up a little.
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Old 05-11-2009, 10:25 AM   #253
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I think I'm going to try setting up a spliff in the rear end of my T/C and see how it goes.
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Old 05-11-2009, 11:09 AM   #254
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It was early in the day, during practice so the bite on the track had not come up yet. It kinda shows how much easier the electric was to drive on a dusty track in comparison to the nitro cars. A smoother torque curve and not having a clutch to snap the drivetrain makes the electric cars a breeze to drive.

One more comment regarding the use of a diff on an 1/8th scale. These cars have been around and in development for decades. They have been driven and tuned by the best of the best. These guys are some of the most innovative racer/developers in the world so they're only concern is to be faster and smarter than their competition. You can rest assured that they have seen and done it all. Some of the things they've tried would make the hair on the back of you neck stand up. I've been around this hobby for close to 20 years and the stories if heard...

Well, simply put as Rich Browne said, "If it made the car any faster, we would be using it".
Typically, we only drive these cars on a prepared racing surface with plenty of traction. They simply won't drive worth s#*t on a dusty playground or parking lot. That's the only place the diff would be of help but we don't race there. So the current setup (solid rear and front oneway) is the way to go.

I hope this clears things up a little.

The speed controls we are using in 1/8th electric are very sophisticated. I am really enjoying the "tuneablity" of these devices. We are using the MMM and the sensored discussion is a non-issue.

The more time I spend on the tuning on the electronics, frankly, the more impressed I am becoming. For 10th scale we are using the KOPRO device - I like the ability to adjust the frequency - very stellar concept. But, the Castle, it's the bomb, for ease of setup and intuitive interface. The Castle has a better front end - the KOPRO seems to be more flexible in execution.

Both just haul ass.

Rick (YoDog) is right, once you know how to setup an 1/8th On-Road - you can put a ton of power down. You should see the drive train components after a One Hour event with a really good driver operating. Geez, these things take some massive stresses.
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Old 05-11-2009, 11:47 AM   #255
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The bottom has been cut!
I just need to countersink the screw holes and it's done.
I've decided not to anodize the chassis since I may need to do some modifications by the time it's all said and done.

It tunes out that the actual machine time comes out to about 40 minutes.
With some adjustments to the program we can probably get it down to under 30 minutes.
I gotta get me a battery...
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