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Weight saving tips

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barrydrink View Drop Down
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    Posted: 18 August 2010 at 6:34pm
I raced at the MuchMore GP at Carlisle at the weekend,
and my Mi4LP was 100g overweight. What's more, the car is
heavier by about 30g on the side opposite the lipo (I
have the motor on the conventional left handside). I was
going to add a bit of weight to the lipo side but that
would make the car even heavier!

So, any tips on saving that 100g and balancing the car?
Or is 30g an acceptable side to side weight difference? I
am using a Demon 5000 lipo, a Spektrum SR3000 receiver, a
SAVOX SAV-SC1251MG servo, Nosram 10.5 motor with Sphere
TC esc and a AMB transponder.

The car is the pro CF version and uses all kit parts.

Thanks,
Barry
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YZFAndy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote YZFAndy Quote  Post ReplyReply Direct Link To This Post Posted: 18 August 2010 at 9:44pm
How are you measuring the weight Side to side? If with the balance tool and a pair of scale on the other end then good. If with a set of scales on each of the four wheels then just make sure you're not measuring uneven spring tension or tweak. To get mine totaly balance i drilled out more holes for the servo to move it forward and out more, now its balance within 5g each corner. To get yours balanced try moving things about first such as sliding the motor in/out its grip or moving the electric about. Even turning your lipo round the other was so the terminals are at the front can shift weigh about.

As for overall weight there is no one thing you can do, it's just a bit of every gram counts. Start with the free weight saving, timing off excess body post length, Don't pump a hole tin of paint on the body shell when spraying it, trim up any excess wire lengths ect (i cut off 35grams on this alone). Other things i tried were Tir (litemodz) driveshafts, which did save quite a bit of weight but the ware rate of them on high grip carpet was ridiculous. Another thing worth look into is your next set of tyres. I run sorex 28's with jb inserts which are 30 grams lighter than the medium inserts ones.

Weight isn't every thing. My last meeting i changed motor and speedo from a lrp spx and lrp x12 to a Gm esc and a speed passion v3 motor which instantly put an extra 60 grams on the car but i TQ and got A1 which was a first for me. The car is easily 100g over weight.

Personal when it comes to balance Vs weigh i would balance the car, especially front to back. You want each wheel to weigh the same or as close as. Think of 15grams out as being your limit.

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MattW View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MattW Quote  Post ReplyReply Direct Link To This Post Posted: 18 August 2010 at 10:34pm
It is possible to make the car very light - but some of it does indeed cost money. When I built my new race car for this year, it came in at 1301!!!

The obvious stuff, titanium screws, titanium turnbuckles, outer pins, ball studs.

Wire makes a difference as Andy says - keep it short. Bodyshells - I alwasy run l/w and they are 15-20g lighter, but obviously don't last as long.

The litemodz driveshafts are a fair bit lighter.
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barrydrink View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote barrydrink Quote  Post ReplyReply Direct Link To This Post Posted: 18 August 2010 at 10:46pm
Originally posted by YZFAndy YZFAndy wrote:

How are you measuring
the weight Side to side? If with the balance
tool and a pair of scale on the other end then
good. If with a set of scales on each of the
four wheels then just make sure you're not
measuring uneven spring tension or
tweak.


Could you elaborate on this please as I'm not
sure I understand the difference. I have been
using the Schumacher pivot block and two
sets of scales but was thinking of getting
more scales in order to weigh every corner
together as I thought that would be a better
way of doing it.

Barry
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kermitt View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kermitt Quote  Post ReplyReply Direct Link To This Post Posted: 19 August 2010 at 1:50pm

Best way is to replace the shocks with turnbuckles of equal length to the shocks so that srping pre-load does not affect the reading on the scales. One turn of a shock collar can make a big difference to the reading.

By far the cheapest and effective method is to measure the centre point on your shock towers and drill a small hole at these points. Then you can pass a thin piece of string between the two holes bearing in mind it must be long enough for you to suspend the car in the air as you hold it up. This way you can add weight as required to get it to sit level whilst held in the air. This way you won't get false readings from using scales because the balance is independant of spring preload.

This is how some other manufacturer's build there shock towers and I wish Schumacher did too.



Edited by kermitt
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qcrc View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote qcrc Quote  Post ReplyReply Direct Link To This Post Posted: 19 August 2010 at 2:01pm
The Mi2EC had notches under the shock tower for that purpose.  I wish that they would have kept that feature as well.
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jo90uk View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jo90uk Quote  Post ReplyReply Direct Link To This Post Posted: 19 August 2010 at 2:15pm
also, on the LP you now have the small holes drilled into the chassis just for this purpose. Put 2 of the balance post thingys nuder the chassis and you can do the same thing.
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kermitt View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kermitt Quote  Post ReplyReply Direct Link To This Post Posted: 19 August 2010 at 2:58pm
The hole on the chassis is not as good for the reasons mentioned above i.e. so that balance can be measured independant of chassis tweak or spring pre-load. Have only seen this on Xray before but Tamiya still have holes in the shock towers on the 415, 416 etc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote YZFAndy Quote  Post ReplyReply Direct Link To This Post Posted: 19 August 2010 at 9:14pm
Originally posted by barrydrink barrydrink wrote:


Could you elaborate on this please
Barry


By using a pair of scales and balance tool you are measuring side to side balance at one end at a time and not tweak or difference in spring loading which you would be by using four scales. Also just because the spring collars are even it doesn't mean to say the springs are millimetre perfect and their preloaded evenly. By using the 3 point system tweak, spring pre-loading will not make any difference to the weight displayed, it will only show you side to side balance. Measure it, then do a collar up tight and measure again to prove my point.

I would also say the balance tool is far superior to the tight rope and shock tower method as this only measures overall side to side balance. For example you could have 750g front right, 250g back right, 250g left front and 750g back left and it would appear balanced.


Edited by YZFAndy
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barrydrink View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote barrydrink Quote  Post ReplyReply Direct Link To This Post Posted: 19 August 2010 at 10:36pm
Originally posted by YZFAndy YZFAndy wrote:



Originally posted by barrydrink barrydrink wrote:

Could you elaborate on
this please Barry
By using a pair of
scales and balance tool you are measuring
side to side balance at one end at a time and
not tweak or difference in spring loading
which you would be by using four
scales.


I'm going to show my ignorance here - I
thought tweak was an unbalanced car but
you say by using two scales and a pivot
block I won't be measuring tweak? So what
exactly is tweak then?

Thanks for your time and patience!

Barry
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YZFAndy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote YZFAndy Quote  Post ReplyReply Direct Link To This Post Posted: 19 August 2010 at 11:02pm
Tweak is a twisted chassis caused by a bash normally meaning the car wont flex evenly and that it can't sit flat and level. Imagine it at the extreme and you could only have three wheels on the ground.

Take all the wheels off and sit the car on a setup board or something you trust is flat like a smooth glass chopping board. Check there isn't any screws or anything else poking out of the chassis then sit it on the board and if there is any kind of rocking the chassis is tweaked.

Not the end of the world if it is, just loosen the four top deck screws, pull, twist and flex about to remove any stress's in it, then push down on the flat board and retighten  top deck screws. If really bad you might need to loosen the translink screws and bulkhead screw also.

Once done remember you may need to reset ride hight, droop
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kermitt View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kermitt Quote  Post ReplyReply Direct Link To This Post Posted: 20 August 2010 at 12:30pm
Running an LP using Ti screw kit, TIR driveshafts, Ti hingepins my car weighs 1380g using LRP X12, SPX & 5300 Lipo, low profile Futaba servo and a small KO 302f receiver running Sorex 28's with JB insert and normal weight body.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote YZFAndy Quote  Post ReplyReply Direct Link To This Post Posted: 20 August 2010 at 1:27pm
Lowest i've had mine down to is 1340g with standard body, x12 motor, spx controller, standard spektrum receiver and a savox servo, trekpower lipo (Lipos vary in wieght a lot also.). Only other bits were tir driveshafts and titanium hinge pins.

One thing i would say is if you're going to spend money on wieght saving then start on the suspention areas first such as ti turn buckles, outer hinge pins and driveshafts. The less unsprung weight you have the more performance increase per £££.


Edited by YZFAndy
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jo90uk Quote  Post ReplyReply Direct Link To This Post Posted: 20 August 2010 at 2:09pm

I agree with the above, spend money first on drive train (less rotating mass helps with acceleration and decceleration) then on things like Ti buckles and hinge pins. Screws will bring the mass down certainly.

Personal ingredietns list would be, in order

Litemodz drive shafts

Litemodz Spool

Ti hingepins and buckles

screw kit

smaller electrics

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Post Options Post Options   Thanks (0) Thanks(0)   Quote YZFAndy Quote  Post ReplyReply Direct Link To This Post Posted: 20 August 2010 at 5:05pm
Litemodz spool is no different in weight than the standard but the non blade design is better.
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Reuben Manning View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Reuben Manning Quote  Post ReplyReply Direct Link To This Post Posted: 20 August 2010 at 6:22pm
get rid of the fan on the TC spec and Titainium
turnbuckles will do. Look at speedmind Titainium screws,
they are super light and fine for top-decks, chassis
bottoms and screws to hold the diff in, dont cost an arm
and leg either.

I am not a fan of the lighter drive-shafts, ive never had
much luck with the 3rd party parts. Not to paint them all
with a Tar brush, but I dont fancy paying out crazy money
just for 16-20g saving, especially not for club level
stock racing.

But to be fair, at club level its not super critical, as
long as your 1400 most, you will be fine.

Making it balanced is better.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote YZFAndy Quote  Post ReplyReply Direct Link To This Post Posted: 20 August 2010 at 6:49pm
Originally posted by Reuben Manning Reuben Manning wrote:



I am not a fan of the lighter drive-shafts, ive never had
much luck with the 3rd party parts. Not to paint them all
with a Tar brush, but I dont fancy paying out crazy money
just for 16-20g saving, especially not for club level
stock racing.


Totally agree with that. I've played with most of it in the way of driveshaft and spools and now its all sitting in the spares box just encase. My spares box is very light but you can't beat the original schie stuff because its tougher, longer lasting and doesn't have a ton of slop in it.
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barrydrink View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote barrydrink Quote  Post ReplyReply Direct Link To This Post Posted: 21 August 2010 at 10:25am
Originally posted by YZFAndy YZFAndy wrote:

Tweak is a twisted chassis caused by a
bash normally meaning the car wont flex evenly and that
it can't sit flat and level. Imagine it at the extreme
and you could only have three wheels on the ground.Take
all the wheels off and sit the car on a setup board or
something you trust is flat like a smooth glass chopping
board. Check there isn't any screws or anything else
poking out of the chassis then sit it on the board and if
there is any kind of rocking the chassis is tweaked.Not
the end of the world if it is, just loosen the four top
deck screws, pull, twist and flex about to remove any
stress's in it, then push down on the flat board and
retighten  top deck screws. If really bad you might need
to loosen the translink screws and bulkhead screw
also.Once done remember you may need to reset ride hight,
droop


So a tweak station is used to get rid of twists in the
chassis? I thought they were for balancing the car...

Barry
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YZFAndy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote YZFAndy Quote  Post ReplyReply Direct Link To This Post Posted: 21 August 2010 at 11:26am
They measure uneven wheel loading. Both tweak and uneven spring preloading can give you uneven wheel loading.  So if your car is balanced, spring preloaded evenly and the tweak station is still showing things are off then you have chassis tweak.
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