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Old 03-03-2006, 09:52 AM   #13126
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Taller pullys???????

Quote:
Originally Posted by F. Alonso
Okay, sorry for sounding a bit dumb, but what is belt wrap?

I'm not sure either but I can make an educated guess. Maybe for example, on a mountain bike you want top speed so then you switch to the smaller gears and you will go fast over time but it takes a lot of power to "spool up" so to speak.
But, when you switch to the taller gears it becomes very easy to pedal and therfore quick initial speed. So maybe on an RC car there is less effort involved on a motor to "spool up" using larger pullys so more bottom end speed and with a mod motor you can attain top speed faster. Does this make sense? Kinda?
Then again, I could be completely wrong!
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Old 03-03-2006, 11:52 AM   #13127
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Quote:
Originally Posted by maxepower
I'm not sure either but I can make an educated guess. Maybe for example, on a mountain bike you want top speed so then you switch to the smaller gears and you will go fast over time but it takes a lot of power to "spool up" so to speak.
But, when you switch to the taller gears it becomes very easy to pedal and therfore quick initial speed. So maybe on an RC car there is less effort involved on a motor to "spool up" using larger pullys so more bottom end speed and with a mod motor you can attain top speed faster. Does this make sense? Kinda?
Then again, I could be completely wrong!
Completely wrong, what you're explaining is gear ratios...

What I was referring to is simply the amount of bending the belt have to undertake to get around the pulley. It's the major cause of drag/inefficiency in a belt driven drivetrain so the bigger the pulleys, the lower the bending and thus the better the efficiency.

This is up to a certain point because if you increase both pulleys diameter without changing the internal ratio, then you increase belt speed, and so the length of belt that has to bend for a similar distance crossed by the car increases aswell, which reduces the efficiency.

Technically speaking what i just explained isn't belt wrap, belt wrap is simply the amount of teeth in contact between the belt and the pulley.
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Old 03-03-2006, 12:02 PM   #13128
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belt wrap is just simply the amount the belt raps around something,in this case the pulleys.
now in theory and i suppose practical terms upto a certain point the amount the belt wraps is greater with a samll pulley[s] and less belt rap is with bigger pulleys.
so belt wrap is the degree of angle the belts turn.
now with a bigger pulley or less belt wrap,this should cause a more free effeciant transmission.were vice versa makes it less effeciant
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Old 03-03-2006, 12:12 PM   #13129
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Surely belt wrap, is the amount the belt wraps round something, so in the example of a small pulley and a big pulley, more of the belt will wrap round the big pulley.

So put the small pulley on the car, install the belt, mark the top and bottom of the belt level with the edge of the pulley, then install the bigger pulley, re-align the top mark on the belt with the pulley and i'm sure the bottom mark will not be level with that top mark any more, therefore more of the belt is wrapped around the pulley.

Now when belt wrap became an issue with the losi xxxs and led to teeth being cut off the belt it was because the belt being a single belt came back around on itself, and a heavy belt caused drag in the transmission, a softer belt, created by the loss of teeth meant the transmission was much freeer.

So, i agree with trfboy, in the 415 less bend in the belt the freeer the transmission.

What do you think ?
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Old 03-03-2006, 12:50 PM   #13130
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Unhappy front uprights

Dear Abbey,

I have searched and searched distributors and hobby shops near and far and this thread. What is going on with the front uprights? distributors are claiming that the front uprights (steering arms) are "temporarily out of production" .. Nobody has them from horizon, great planes, speedtech, to even tamiya themselves. Somebody walk over to Mr Chin, if you find the right one in the phone book, beat him in the head with some bamboo and flip the switch on the machine. Its been 3 months since I've seen it in stock anywhere.

What's going on? Is there a new part # that I'm not finding? I'd consider going aluminum if i could stock up on enough shims/hinge pins when the arm breaks. The front uprights and the kingpin set are the only things I can break on the car. Doubles of towers, arms, hubs(rear anymore) and belts sit in the box in case something breaks. So now the car sits on the table begging me to strap on a set of freshies, open up a can on the guys but I'm done with ca'ing steering parts back together. I have the hpi arm (modification for parma? foams) on its way but if I felt the need to own an x-ray, i would have bought x-ray. atleast there the guys hear "its on its way" or "two weeks" or "its in customs" or "we were waiting for everything to come in before we ship it"

new cars (or kits) mean nothing if you can't supply the crossover parts for them.

signed,
Mr. re-reglued steering arm re-reuser.
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Old 03-03-2006, 01:28 PM   #13131
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Quote:
Originally Posted by Mason
Dear Abbey,

I have searched and searched distributors and hobby shops near and far and this thread. What is going on with the front uprights? distributors are claiming that the front uprights (steering arms) are "temporarily out of production" .. Nobody has them from horizon, great planes, speedtech, to even tamiya themselves. Somebody walk over to Mr Chin, if you find the right one in the phone book, beat him in the head with some bamboo and flip the switch on the machine. Its been 3 months since I've seen it in stock anywhere.

What's going on? Is there a new part # that I'm not finding? I'd consider going aluminum if i could stock up on enough shims/hinge pins when the arm breaks. The front uprights and the kingpin set are the only things I can break on the car. Doubles of towers, arms, hubs(rear anymore) and belts sit in the box in case something breaks. So now the car sits on the table begging me to strap on a set of freshies, open up a can on the guys but I'm done with ca'ing steering parts back together. I have the hpi arm (modification for parma? foams) on its way but if I felt the need to own an x-ray, i would have bought x-ray. atleast there the guys hear "its on its way" or "two weeks" or "its in customs" or "we were waiting for everything to come in before we ship it"

new cars (or kits) mean nothing if you can't supply the crossover parts for them.

signed,
Mr. re-reglued steering arm re-reuser.
thats strange that you cant find any of these parts.
ive never seen these break but i have had the front hub screws come out because of a stripped thread.
ive never seen them break completey though.
if you use hpi front huibs you need to put a 1mm shim in otherwise you get alot of up and down movement.
also remeber them bearings.there not the same size as the standard bearings.i cant remeber what size they are,someone here will know.

jakeburns

surely more belt wrap means it wraping more round a pulley?there fore i woulda thought would give a littler pulley thus less effeciancy
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Old 03-03-2006, 01:35 PM   #13132
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Quote:
Originally Posted by Crashmaster
Ed,
Have you just ordered the diff pulleys then, or the layshaft ones aswell? Any chance of some part no's aswell.... lol

Cheers
Dan Chambers
Just the diff pulleys... I don't see the point of the plastic ones, given the number of teeth is still the same.

I'll try and ask david about them on sunday... see if I can get a better understanding of reasons for using them (and I'll check to see if he uses them as well )

On another point entirely... if anyone looses the small screws for the alloy top brace, or one way screws, these guys are awesome www.modelfixings.co.uk, specifically http://www.modelfixings.co.uk/miniature_cap_screws.htm
ordered them on wed night, arrived this morning... all for the royal price of less than a fiver

Laters
Ed
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Old 03-03-2006, 01:49 PM   #13133
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Originally Posted by TryHard
Just the diff pulleys... I don't see the point of the plastic ones, given the number of teeth is still the same.

I'll try and ask david about them on sunday... see if I can get a better understanding of reasons for using them (and I'll check to see if he uses them as well )

On another point entirely... if anyone looses the small screws for the alloy top brace, or one way screws, these guys are awesome www.modelfixings.co.uk, specifically http://www.modelfixings.co.uk/miniature_cap_screws.htm
ordered them on wed night, arrived this morning... all for the royal price of less than a fiver

Laters
Ed
can you also ask him what his opinions on tyre warmers are and how he uses them,since his not racing nationals i suppose no point in asking in his mind which tyre would be the best in his opinion.
alot of people are saying that tyre warmers bring the tyres a lot more grip.
some even saying to the point of grip rolling.
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Old 03-03-2006, 01:51 PM   #13134
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Quote:
Originally Posted by TryHard
Just the diff pulleys... I don't see the point of the plastic ones, given the number of teeth is still the same.

I'll try and ask david about them on sunday... see if I can get a better understanding of reasons for using them (and I'll check to see if he uses them as well )

On another point entirely... if anyone looses the small screws for the alloy top brace, or one way screws, these guys are awesome www.modelfixings.co.uk, specifically http://www.modelfixings.co.uk/miniature_cap_screws.htm
ordered them on wed night, arrived this morning... all for the royal price of less than a fiver

Laters
Ed
Are u going to the euro's this weekend?
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Old 03-03-2006, 01:55 PM   #13135
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Quote:
Originally Posted by C van der Hagen
Are u going to the euro's this weekend?

does the euros start this weekend?
i didnt know that eeek,lol
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Old 03-03-2006, 02:11 PM   #13136
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Quote:
Originally Posted by C van der Hagen
Are u going to the euro's this weekend?
Is it the Euro's??
whoops... thought he was gonna be at the final Carpet Wars meeting.
Bit early in the year for euro's aint it?? Maybe cause the worlds are in europe this year, they are running it earlier.

Cheers
Ed
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Old 03-03-2006, 04:25 PM   #13137
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Quote:
Originally Posted by TryHard
Is it the Euro's??
whoops... thought he was gonna be at the final Carpet Wars meeting.
Bit early in the year for euro's aint it?? Maybe cause the worlds are in europe this year, they are running it earlier.

Cheers
Ed
1/12TH EUROS not TC euros...
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Old 03-03-2006, 07:10 PM   #13138
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The problem with the belt wrap improvements you guys are talking about is that you increase efficiency in one area and reduce it in another.

Buy increasing the diameter of the pulley, the belt doesn't have to follow as tight a bend as previously, and this increases efficiency.

However, as the pulley diameter increases, so does the number of teeth which are in contact with the belt at any given moment, - and this reduces efficiency.

And it's just as complicated if you only change (for example) the diff pulley.

If you increase the size of the diff pulley, you lose efficiency by increasing the number of teeth in contact with the belt, but you gain efficiency by increasing the bend-diameter the belt has to travel over the pulley, but you also increase efficiency at the layshaft pulley because the belt angle to the layshaft has been reduced, therefore there are now less teeth in contact with the layshaft pulley!

Of course, one thing that is forgotten is belt tension, which severely effects efficiency:
bigger pulleys = more teeth in contact with the belt = looser belt tension possible = better efficiency
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Old 03-03-2006, 08:47 PM   #13139
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Just checked Tamiya USA's site and they list the 415 4mm chassis as "See your local hobbyshop". Anybody have any details about its release?

Thanks,
Jimmy
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Old 03-03-2006, 11:32 PM   #13140
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Does anyone have a good stock asphalt rubber tire setup to share?
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Last edited by nordheim; 03-03-2006 at 11:34 PM. Reason: Typo
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