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Old 12-10-2004, 10:53 AM   #1456
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Originally posted by Robz
Hey guys, you probably all hate me anyway cos i didnt agree with all you guys about the short arms. Anyway, another update from the weekend that the one of the UK team drivers totally gave up with the car, nothing he tried would make it work, the rear end just wouldnt work, went straight back to the XXX-s. I believe that when all you normal drivers go and spend money on them you will then find out it will only work in certain circumstances, only very high grip and very flat. Another thing, i read that you guys all think the transmission is really free. Well that is the amount of rotating mass on it. The pulleys in the centre are steel type material and very large, the long diff half section is metal, everything is very heavy. Thats why it spins for ages when tested. Just thought id add an opinion, you guys will all say im wrong anyway but thought id let the open minded person get both sides of the storey.

Rob
Yes you are brutal for judging something that you have not even run. The pullies that are on the center of the car are plastic and aluminum and not steel. Also this car does have a freer drivetrain than the XXX-S. Why??? Well the belt does not have a chance to rub the bottom of the chassis so this helps with efficiency. Also neither the front or rear belt has a S-bend in it like the XXX-S. If you knew anything about belts you would know that as soon as you bend a belt it looses efficiency. So by bending the belt twice in the S bend would hurt efficiency. The new car only bends the belt once on each end of the each pulley.
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Old 12-10-2004, 10:56 AM   #1457
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Old 12-10-2004, 10:59 AM   #1458
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Quote:
Originally posted by Robz
that aluminium coupler is what weighs alot, the outdrives are also huge, even thoughn they are plastic they are massive. Im only telling you how it was about those driveshafts. One of the Uk team drivers JUST got them to last a run, the other COULDNT, with the motors they were running they fell apart, runs where he went back to the old shafts was .2s lap slower and couldnt last 5 minutes because the inefficiencies of the spool chatter caused the motor to unsolder. Trust me they were breaking, just hope they get sorted before being released.
Yes this is true that the new front drive shafts do help the lap times quite dramatically. I think once we make the new LCD(Losi Constant Drives, patent pending) for all other cars their laptimes will decrease when running a spool. All of the cars chatter with standard CVD's and spools. The new LCD's simply take all the chatter out of the car. Also they are made of steel not aluminum. Also the parts were breaking like you mentioned. However this was the first prototype of thei LCD. We have since made changes to the new LCD to make it last as long as a CVD or longer.
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Old 12-10-2004, 11:01 AM   #1459
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Old 12-10-2004, 11:03 AM   #1460
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Quote:
Originally posted by T. Hodge
Also the parts were breaking like you mentioned. However this was the first prototype of thei LCD. We have since made changes to the new LCD to make it last as long as a CVD or longer.

So at Halo you were running the revised version?

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Old 12-10-2004, 11:03 AM   #1461
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Old 12-10-2004, 11:08 AM   #1462
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Originally posted by Robz
Maybe you should weigh all the rotating mass on the car and compare it to that of TRF.
Actually, one of my good friends run for Tamiya, and two others have the TRF 415. I have handled this car very much.. infact, if not for the JRXS comming I would probably be driving this car... anyway- this is NOT the free-est car I have ever felt. It is almost street-weapon-ish.. well, maybe not that bad.. Yes, they all had the new white belts, yes, they all know how to build smooth drivtrains...
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Old 12-10-2004, 11:12 AM   #1463
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Old 12-10-2004, 11:22 AM   #1464
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An object in motion, stays in motion... it like the first law of physics...

if wheels on car X spin longer than the wheels on Car Y, and all other variables are the same (weight of wheel)... it is safe to say, within reason that car X has a more efficient drivetrain.

although I do hear that shaft cars are more efficient upon accelleration, and not at speed.. i tend to believe my own findings based on common sense and YEARS of experience..

now the exception to the rule.. LOL.. the original run of Yokomo SD's.. I actually ran for yokomo when this car was still pretty new.. My car, when i was done with it.. gees.. you could spin the wheels, go to lunch and come back and they would still be spinning... unfortunatly, the car was a dog in stock. I finally came to the conclusion that the tranny gears were made of soft plastic, and absorbing all of the energy. Noone wanted to listen to me... haha... but now a year later LOOK.. theyre pulling gears out of graphite.. hmm..

just my opinons-

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Old 12-10-2004, 11:28 AM   #1465
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Old 12-10-2004, 11:33 AM   #1466
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Originally posted by Robz
yeah but the variables are not the same obviously, the mass of rotating parts is different, every cars has different parts and these have different weight. The wheel was an analogy. Its best to do it without wheels as the wheel is large with large mass and distorts the feel of how much weight is in the drivetrain. Obviously its advantageous to have large pulleys to make the belt bend less severe and efficiency gained, just dont make rotating parts with much weight to them.
yes, but the trannys are not variables.. they are controlls.. they are what you are comparing.. control vs. control with 1 variable= CAR X vs. Car Y = the 1 variable being the wheel.
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Old 12-10-2004, 12:12 PM   #1467
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Also, the spin test is very inaccurate when comparing shaft to belts. Belts get more efficient the faster they spin due to centrifical force making the belt looser.
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Old 12-10-2004, 12:41 PM   #1468
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Also, the spin test is very inaccurate when comparing shaft to belts. Belts get more efficient the faster they spin due to centrifical force making the belt looser.
see, i disagree with that. Unless the belt is stretching, it cannot get "looser". Slack in the belt can move to different areas, but to actually get "looser" would be impossible, unless you take in account heat expansion... and stretching when the belt it new...

The belt on the XXXS is pretty tough. If you have ever held one out of the car, and pulled.. they really have a lot of stregnth.
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Old 12-10-2004, 08:33 PM   #1469
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Quote:
Originally posted by Keith Billanti
see, i disagree with that. Unless the belt is stretching, it cannot get "looser". Slack in the belt can move to different areas, but to actually get "looser" would be impossible, unless you take in account heat expansion... and stretching when the belt it new...

The belt on the XXXS is pretty tough. If you have ever held one out of the car, and pulled.. they really have a lot of stregnth.
You know i Really think that the faster the belt spins on a pully the less friction/ looser belt. When i was younger i Took an old Suzuki motorcycle frame and put a Brigs & Staton Race engine in it and make it belt drive. when the bike got to a certain speed it felt like it shifted gears and it started to gain more speed. all i can figure is the belt expanded to create that effect, kind of creating a second gear ratio.
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Old 12-10-2004, 08:56 PM   #1470
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Jack Smash is correct - belt drives become more efficient as speed increases, whereas shaft drives are less efficient as speed increases. There's a lot of technical, scientific reasons for this, but if we start down that path, these "discussions" will never end

On a side note, fine pitch belts (mxl) are much more efficient than the medium pitch belts used in most current rc cars, as they can be pulled around a smaller diameter pulley, therefore it's possible to reduce rotating mass by having smaller layshaft / diff pulleys - but the tradeoff is they get damaged by dirt etc very easily plus belt tension is much more critical, so I wonder if Losi investigated using these belts?

Back to the car- We'll just have to wait until it's released to see what materials they use for the parts etc, but I think it's safe to say, based on current race performance, that it's going to be damn competative, regardless of what reservations people have about the design
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