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Old 07-01-2005, 07:45 AM   #7696
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AI - Aluminim is definately stronger than plastic and the same "grinds" can be made to the aluminim. Either way anything to avoid removing /installing the rear brace is a worthwhile thing. Because I seem to have to remove my brace frequently ( different track use different engines, clutch set-ups, etc) my screws no longer allow to be properly tightened down. Or shall I say the plastic threads are pretty much gone now

I have to chuckle here... you or myself have no "accurate" way to understand the stresses going on in that cross brace... so let's just leave that issue alone - the only real way is to run a mechanical stress analysis with an accurate model which you or I don't have resources to do.

... now off to my first day of school in " .. how to properly torque a machine screw into plastic..." I have a feeling this is going to be a tough one for me
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Old 07-01-2005, 08:08 AM   #7697
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I can say its an educated guess. But the plastic flexes pretty bad. I did test that. I thought with its design it might be ok. But it still had quite a bit of flex. Reason why I said screw it and im going to give it a try.

You can only figure the stresses its going by though no matter if we know exactly or not. Racing is all about educated guesses, at least in our budget. I mean knowing to scale this thing is doing 600mph over terrible roads. We knows its getting an enormous amount of vibration and bouncing and we know if it a part is flexy. Its going to flex in that situation. So put that all together and what do you got.

I mean we know its not going to make the car flex more with this part right. Of course not. Stay the same, probably not as the aluminum cant be flexed by hand while the plastic can be bent a good inch or so. So we pretty much can figure this is going to enhance things.

Also when I had my old rs4-2. When I upgraded to the cf upper deck from the plastic. The car took on this all around stiff feeling when grabbing it from the rear bulk-head. Oddly enough im sitting there with the car beforehand and I always thought the r40 was pretty stiff.

But afterwards it seemed to have that same effect. What im feeling is basically more fight. Because the car is now staying straighter. While before it could bend that ever slight bit adjusting how it feels in your hand. Especially when holding the rear bulkhead.

I always grab the car this way too. So when I finally did install the part I thought wow that does feel more stiff now. And thats just holding it.

I of course cant see anything or verify but I do swear I feel something and I wouldnt bring something up unless It was that way. Luckily the parts easy to swap out so maybe I can swap back and check.

But take a good look at that area. Once I installed the aluminum part I was thinking holy crap why not sooner. Its pretty obvious its going to enhance the chassis stiffness and overall togetherness. At least imo.

Get the 3racing one and see what you think on your setup if your familiar with it, I bet you will find improvement. Honestly I can gurantee this helps the chassis. Even if my car handles funky after this. Im going to adjust to it cause im a big believer in stiffening the chassis.

Because you can always tune your suspension but you cant tune chassis flex.
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Old 07-01-2005, 12:49 PM   #7698
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actually when i first installed the brace one of the screws didnt feel like it threaded at all. i didnt feel any opposing forces or pressure while screwing it in... i got new screws and i am gonna see if it works out better. i was thinking of the alum one but then i thought...wait where am i gonna put the throttle return spring now since its hooked onto a small hole on the brace maybe i can reduce the flex with a tighter fit on the screws... dunno gonna have to try but first i gotta put my engine back in.... as for the springs ill show a pic of them.
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Old 07-01-2005, 04:33 PM   #7699
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Hara or the HPI team have never used the aluminium right side brace. This brace in fact is not intended to brace the car in any direction but fore-aft. Similarly with the left side brace. If you look at all the top nitro cars, MTX3, V1RRR etc none even have the left side brace that the HPI has. In the last worlds Adrien Bertain used a V1RRR with only 1 side brace that also is quite flexible (less so than the HPI but the HPI has 2)

Point is the cars need some chassis flex in this area to work and Hara has won 2 ROAR championships without stiffening the car up here.
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Old 07-01-2005, 05:13 PM   #7700
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Quote:
Originally Posted by AMGRacer
Point is the cars need some chassis flex in this area to work and Hara has won 2 ROAR championships without stiffening the car up here.
AMGRacer, ideally you want to reduce or completely eliminate chassis flex and let the suspension do all the work to get a predictable and balanced setup, any Compliance in the chassis is undesirable. This is just general race car dynamics.
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Old 07-01-2005, 05:25 PM   #7701
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Quote:
Originally Posted by AMGRacer
Hara or the HPI team have never used the aluminium right side brace. This brace in fact is not intended to brace the car in any direction but fore-aft. Similarly with the left side brace. If you look at all the top nitro cars, MTX3, V1RRR etc none even have the left side brace that the HPI has. In the last worlds Adrien Bertain used a V1RRR with only 1 side brace that also is quite flexible (less so than the HPI but the HPI has 2)

Point is the cars need some chassis flex in this area to work and Hara has won 2 ROAR championships without stiffening the car up here.
I do believe as well you can win with the stock piece. I just like how it feels and Im the same way. I race real cars as well. I always have been a big believer in a stiff chassis as a base. The rear brace, out of all the parts I have as hop-ups sitting in there bags waiting. Im going through them all one by one weighing them all , checking flex and and im pretty sure this is worthy.

Ill let you guys know. Race is this sunday. Ill be honest if I felt anything or not. Otherwise its a 4gram weight gain and if im not saying yeah its better....off it goes.
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Old 07-01-2005, 05:30 PM   #7702
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Quote:
Originally Posted by AMGRacer
Hara or the HPI team have never used the aluminium right side brace. This brace in fact is not intended to brace the car in any direction but fore-aft. Similarly with the left side brace. If you look at all the top nitro cars, MTX3, V1RRR etc none even have the left side brace that the HPI has. In the last worlds Adrien Bertain used a V1RRR with only 1 side brace that also is quite flexible (less so than the HPI but the HPI has 2)

Point is the cars need some chassis flex in this area to work and Hara has won 2 ROAR championships without stiffening the car up here.

didn't I read somewhere,that not only was he not using the metal brace,he actually loosened the screws in the engine brace..?....

Btw,Thad Garner at HPI told me to use the stock brace also...and run the flexible HPI brace on the other side,too....(off course,I'm not...but thats another story... )
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Old 07-01-2005, 05:49 PM   #7703
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Quote:
Originally Posted by fastharry
didn't I read somewhere,that not only was he not using the metal brace,he actually loosened the screws in the engine brace..?....

Btw,Thad Garner at HPI told me to use the stock brace also...and run the flexible HPI brace on the other side,too....(off course,I'm not...but thats another story... )
Hum, if hara finds the car handles better after increasing the torsional movement of the chassis then that says something about the suspension geometry of the r40 or maybe he likes the way the car handles with such a strange setup, maybe suits his driving style or sumit.

At the end of the day any movement the chassis makes the suspension will have to compensate, not really good practise.
I cant wait to see how this car handles now!!
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Old 07-01-2005, 07:38 PM   #7704
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Quote:
Originally Posted by fastharry
didn't I read somewhere,that not only was he not using the metal brace,he actually loosened the screws in the engine brace..?....

Btw,Thad Garner at HPI told me to use the stock brace also...and run the flexible HPI brace on the other side,too....(off course,I'm not...but thats another story... )
Thats interesting. I wonder why they wouldnt opt for it. I also wonder how much time they put into testing setups. Im sure its a lot of time since they have so much to go through.

Even though I still want to try this versus the other option parts for the car. Ill be sure to bring the stock plastic piece to the races though.

Thanks for the info.
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Old 07-01-2005, 09:28 PM   #7705
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Hi again, just another general nitro question. I know that it generally isn't "recommended" to use rechargable AA batteries for the reciever, due to the fact that they lose voltage very quickly. I am just wondering if it would be fine as long as I just charged them up again after about every 2 runs on them. This isn't a problem because I don't do any official racing, just bashing, and I have about a gazillion rechargable AA batteries. Please private message me with the answer, because I have trouble keeping up with the answers to my questions due to how fast this thread moves. Thanks! Oh, wait, one more question, how much money could I expect to spend adding a reverse to my low end truck?
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Old 07-01-2005, 09:30 PM   #7706
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Quote:
Originally Posted by Hesky
AMGRacer, ideally you want to reduce or completely eliminate chassis flex and let the suspension do all the work to get a predictable and balanced setup, any Compliance in the chassis is undesirable. This is just general race car dynamics.
Yes I know that, but that theory applies for 1:1 full sized racecars. You are not in these cars are you? They are not like 1:1 full size racecars where you can feel everything through the chassis.

Here is a question. Why do companies like XRAY, HPI and many others offer less stiff side braces in their gas cars and more flexible chassis and top decks for their electric cars? Why did Hara use a thinner top deck and bottom deck on his pro 4 to take 2nd place at the worlds?
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Old 07-01-2005, 09:31 PM   #7707
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Quote:
Originally Posted by Artificial-I
I do believe as well you can win with the stock piece. I just like how it feels and Im the same way. I race real cars as well. I always have been a big believer in a stiff chassis as a base. The rear brace, out of all the parts I have as hop-ups sitting in there bags waiting. Im going through them all one by one weighing them all , checking flex and and im pretty sure this is worthy.

Ill let you guys know. Race is this sunday. Ill be honest if I felt anything or not. Otherwise its a 4gram weight gain and if im not saying yeah its better....off it goes.
Yep if you like it knock yourself out I hope it works out for you. My experiences are very opposite to what you are saying is all, take that with a grain of salt.
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Old 07-01-2005, 09:32 PM   #7708
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Quote:
Originally Posted by fastharry
didn't I read somewhere,that not only was he not using the metal brace,he actually loosened the screws in the engine brace..?....

Btw,Thad Garner at HPI told me to use the stock brace also...and run the flexible HPI brace on the other side,too....(off course,I'm not...but thats another story... )
You got it Harry. People can get too obsessed with an ultra stiff car. I have done it myself before today and what you can end up with is a car that is VERY VERY darty and extremely difficult to drive.
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Old 07-01-2005, 09:35 PM   #7709
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Quote:
Originally Posted by Hesky
Hum, if hara finds the car handles better after increasing the torsional movement of the chassis then that says something about the suspension geometry of the r40 or maybe he likes the way the car handles with such a strange setup, maybe suits his driving style or sumit.

At the end of the day any movement the chassis makes the suspension will have to compensate, not really good practise.
I cant wait to see how this car handles now!!
What you are forgetting is that a CONTROLLED chassis twist is not a bad thing if designed right. It acts as you say as part of the suspension. Some Formula 1 cars have used the inherent flex in their tie rods as the spring rather than using an actual spring itself.

Why RC cars need some twist is purely and simply that they are easier to drive.
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Old 07-01-2005, 10:54 PM   #7710
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I think I can see your point, above all its the way the car handles that matters and if using a bendy chassis helps then it has to be done. just finding it hard to get my head around this 'controlled' chassis twisting, I mean 'scale' is the word here and when we're talking about suspension dynamics the SAME theory apples to 1:1, 1:5, 1:10 just as aerodynamics does hence why there are scale aerodynamic test tunnels for motor racing.

With regards to F1 cars I'm guessing when you talk of flex you mean the anti-roll bar or torsion spring passing trough the middle bell crank linkage fixed to the chassis, these bars serve a different purpose much like the sway bar of our rc cars. This bar has nothing to do with spring rate, and has a different effect on handling than a bendy chassis. F1 chassis are as rigid as they come! really the only components that compress or flex on an f1 car are the spring's, the arb's and tires. these bar the tires are easy to CONTROL,the chassis is much harder to measure, rate and adjust so this is why its not designed to flex and its is not really desirable when they do so.
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