My 5T/5SC Project

Not your average Savage Hop ups. These are highly modified, with some home-made parts.

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FluxNZ
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Re: My 5T/5SC Project

Post by FluxNZ » Mon Oct 28, 2013 10:55 pm

Thanks Johny for the input.

I was looking over one of my old videos of when I first ran the truck with the 2028 which was running in 2WD drive and it wasn't cogging like the current setup was so it could very well be the gearing seeing it's trying to push all 4 wheels now.

Largest spur gear I have is a 50T so that's the highest I can go there.

The Baja 5B Flux weights in at 9.5kg's without batteries (maybe 11kg with batteries like mine) and is gear with a 57T spur with a 14T pinion but people are running them with 16T and 18T no problem.

I'm 9.3kg total and have a 50T spur to work with. What pinion size would be best to match the 5B flux setup? The lowest I can go is an 18T for the 8mm shaft. Other sizes up from there at 20T, 23T, 25T, 28T etc. Would like to reach top speed of 100kph or more :wink:
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Post by johny723 » Tue Oct 29, 2013 6:00 am

What is the speed with the current gearing?

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Post by lizard » Tue Oct 29, 2013 8:48 am

Absolutely great ride you have created there.

Just some thoughts I may add.

Diffcups breaking in half:
modules.php?name=Forums&file=viewtopic& ... ht=#873609


Castle XL2 Cogging:
Seems to be a known problem with the castle XL2 I have read about it on other forums and I myself have similar (but not so bad) problems when I use high gearing with my Mamba Monster Extreme from the XO-1 with v1.32 firmware. Seems to happen when the load get's very high with heavy cars and heavy tires and high gearing. I guess the only thing you could do is wait for castle to hopefully fix it with a firmware update. As far as I have read, it can be mitigated a little by using high C batteries, it seems to get worse when voltage drops too much under load. You could also try to use the Torque-Control feature (if the XL2 has that), it should also limit currents.

BTW, the XL2 in othello's thread on RCMonster died a few days ago, probably because the rotor of his 1717 was demagnetized. It died after shortly applying throttle and cogging. He then connected an EZRun 150A ESC and it was able to move the car (although the wires and everything got hot very quickly). Quite interesting to see, that a much smaller and cheaper ESC can apparently withstand more abuse.


Center Diff Oil:
I had 500.000 cst Oil in my 5.4Kg Castle 1717 powered truggy and the front tires were still balooning and the diff would get pretty hot after a while. Now I have 2.000.000 cst Oil in it and it's good, no more balooning. With the weight and power of your truck I would recommend 2.000.000 or even more to get rid of balooning and for better braking power.

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Post by johny723 » Tue Oct 29, 2013 9:14 am

check this link http://www.clearcoproducts.com/pure-sil ... osity.html they sell silicon oils up to 20,000,000 cSt :twisted:
they sell it for industrial pursposes in gallons, but it is worth trying to persuade them to sell you some smaller quantities :D

regarding the cogging, I dont think it is caused by overgearing. A stock flux baja is advertised by HPI to reach 60mph, which is roughly 100km/h, so I dont think that your problems are caused by overgearing, unless you have some really tall gearing

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Post by lizard » Tue Oct 29, 2013 9:50 am

Hey thanks for the link, I have been looking almost everywhere for something higher than 2 Million cst. Atleast a little hope.

I am using the stuff from:
http://www.silikon-profis.de (sorry, german only)

LMI Racing also seems to have 2.000.000 cst Oil.
http://www.redrc.net/2012/06/lmi-racing-silicone-oil/


Regarding the cogging:
Sorry, maybe I wasn't clear. What I mean is, that this is actually a 'castle-problem' (because with other ESCs you can run high gearing without cogging), but it seems to get worse with high gearing, high load (heavy tires and car) and batteries that are not brandnew and top-notch.

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Post by FluxNZ » Tue Oct 29, 2013 11:27 am

Thanks for the info guys. I can see the front end does spin up a bit so getting a thicker centre oil in there would help.

I'll start by reducing the gearing to see if that will help. I'll be going down a few teeth on the pinion and will keep dropping the pinion size to see what happens if the first go doesn't help. Worth doing this first to sort out what is going on.

[youtube]
[/youtube]
Video of the truck with the 2028 and 2WD. No cogging issue there.
Savage Flux HP - Mild Mods.
Savage Flux 5SC/5T - Custom built.
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Post by johny723 » Tue Oct 29, 2013 6:46 pm

I just did some math and found out that if you use 28t pinion, 50t spur, and tires with 17cm diameter, 3,8V as the voltage of each cell, then the top speed is around 132km/h, which might be actually overgeared even at a lighter weight!
My calculations are quite rough, I dont know the precise pinion and spur and tire size, but it seems that the truck really is overgeared.
It is hard to believe, but you managed to overgear even the 2028! :D

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Post by FluxNZ » Tue Oct 29, 2013 6:55 pm

To be honest there may have been a hint of cogging in that video while taking off from a stand still at some points. Gives me an idea what size pinion I could use from the original one used.

Like lizard said it's known problem with the XL2 to have cogging but I'll try the pinion first. I think a 23T or 25T maybe the sweet spot and still get 100km+ from it which I would be happy for it.

Well I can get some Tamiya 1000000 diff oil off Ebay which is handy but can't find anything else that is heavier like those ones you have listed. Anyone else have luck with different search options?

http://www.ebay.com/itm/Tamiya-54419-OP ... 2ec90cdefa
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Post by johny723 » Tue Oct 29, 2013 7:29 pm

2000k from LMI can be had here 2000k from LMI racing http://www.lmi-racing.com/lmi/lmi-diffoel-2000000.php
I dont think ebay is a good source for such items.
The best way will be directly contacting the companies who make them for industry like the one I linked and beg them for a small quantity of the silicone oil :(

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Post by FluxNZ » Tue Oct 29, 2013 7:59 pm

I could try to contact them but I do remember I've ordered off the German Ebay before for the FG tie rod ends once.
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Post by FluxNZ » Thu Oct 31, 2013 2:37 am

Are there any other spur gears higher than 50T for the HB diff cups? Just giving myself more options for tuning.
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Post by lizard » Thu Oct 31, 2013 7:44 am

Kyosho spur gears also fit the HPI diffs.

But, to be honest, I don't think that the plastic Vorza diffs will last long with your heavy rig in combination with that motor.
They have some problems:

- The crosspins will eventually wear into the diffhousings (that's why HPI has made those square metal blocks on the Savage Flux diffs) and throw off the mesh of the inner gears eventually
- The crosspins will wear down where the 4 small spider gears ride on them, also throwing off mesh eventually.
- The 2.5mm pins that drive the outdrive cups are prone to break.
- The sungears sometimes split in half (this might be connected to or caused by broken 2.5mm pins)
- The 9t pinion gear of the bulletproof diffs don't seem to be really bulletproof. On a stock savage Flux, the rear pinion tends to lose teeth. On your rig it might actually not be an issue because of your center diff "smoothing out" torque peaks, but considering the weight and power of your ride, I would not bet on it.
- Another issues with those Vorza diffs is, that you have to use shims inside the diff to properly mesh the gears. In my experience, thinner shims (0.1 and 0.2mm) tend to wear down eventually and thus throwing the mesh off again

I would suggest getting three CEN GST 7.7 front or rear diffs from ebay (about 35$ each). They do not have crosspins as they are "LSD-style", use 3mm pins for the outdrive cups, don't need shimming inside, have stronger internal spider gears and the ring and pinion gear is stronger also. For the center CEN diff you can use Associated RC8T spurs, they are reasonably priced and available from 44t to 54t, or the ones from the CEN Matrix buggy or truggy or GST-E, they are available in 46t and 66t.

If you want even stronger front and rear diffs, I would suggest getting the new Hot Racing Savage Flux spiral cut ring and pinion gears, and use them in combination with the CEN GST 7.7 diffs. Only downside is, you would need to custom-make a special diffhousing because the screw holes do not align between HPI and CEN.


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Post by FluxNZ » Thu Oct 31, 2013 11:28 am

So any Kyosho spur off one of their 1/8 buggies with work? Having the option of a larger spur can help me clear the motor can if I start to drop the pinion sizes too low.

Your a wealth of knowledge Lizard so thanks for sharing that info which I'll be needing some short time in the future I think.

I'll keep testing and see what fails first. It's a good test bed to see how things last due to the weight of this thing.
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Post by lizard » Thu Oct 31, 2013 11:57 am

I am not sure if something on the newer Kyosho cars has changed, but probably not. I have once used one from a Inferno MP7.5 buggy, that definitely fits. Back in the nitro days when there was no Vorza and no CEN, a common way of getting rid of the poor 10x16 bearing was to use Kyosho IF-103 diffhousings, the holes on it are the same as on HPI diffs, so if you find a spur that fits that housing it will also fit HPI's diff housings.

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Post by johny723 » Thu Oct 31, 2013 12:46 pm

I have CEN GST diffs in my truck and they are ok, but aluminum diff cup is made of is rather soft
I also found several people say that Cen diffs do not use machined ring/pinion, but cast, which is not as strong as the machined.
On the other hand, they are rock solid, use 3mm pins and strong internal gears, but they require lots of shimming.

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Post by s2022 » Thu Oct 31, 2013 1:48 pm

[quote="FluxNZ";p="874317"]So any Kyosho spur off one of their 1/8 buggies with work? Having the option of a larger spur can help me clear the motor can if I start to drop the pinion sizes too low.

Your a wealth of knowledge Lizard so thanks for sharing that info which I'll be needing some short time in the future I think.

I'll keep testing and see what fails first. It's a good test bed to see how things last due to the weight of this thing.[/quote]

I have some Kyosho center diffs from my MP 7.5, they fit the savage diff, in fact I have the spur gears between HPI, Kyosho and HBodies all mixed up in a box, and as i recall they are almost all interchangeable, even the screws are the same spacing.
[color=blue]Regards
RCS2022[/color]
[color=blue][i][url=http://www.savage-central.com/modules.php?name=Forums&file=viewtopic&t=93732]Savage Flux XL; Mamba XL2; 1717; Custom CD; Mech Brakes[/url][/i][/color]

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Post by FluxNZ » Thu Oct 31, 2013 1:53 pm

Any chance you could post up some photos of the parts together or just in bits so I could see them :)
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Post by lizard » Thu Oct 31, 2013 1:58 pm

As far as I know, the CENs are sintered. Machined gears should be stronger that's true, but somehow the HPI ones are not, forums are full of reports of broken 'bulletproof' pinions. My stock flux pinion broke on the 10th pack or so, after that I installed the CEN diffs I used in my old nitro Savage before (with several gallons of hard bashing with a Novarossi 528XRP on them) and they hold up fine until now.

The diffcase is rather soft alloy, thats true, but okay, because there is no point where it needs to be strong because it doesnt use crosspins and thus the force is spread on a large surface area due to the LSD blocks that thespider gears sit in. Maybe stripped threads could be an issue, but so far I had no problems and I always tighten the diff screws very hard. Even if you strip a thread somehow, the cases are cheaper than any other alloy diffcase. Whats also very nice about the screwholes is, that they go through the complete case, so if grease gets in accidently

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Post by johny723 » Thu Oct 31, 2013 3:46 pm

yes, they definitely have some potential. Too bad the BP ring does not fit the cen cup. That would be probably the strongest diff of all

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Post by s2022 » Fri Nov 01, 2013 3:02 am

Here are the pics, From memory, the complete diff is a HB VE8 diff,
top right, used spur is the Vorza
The bot left is a GS racing 46t Spur, haven't reied it yet, but seems would for the Vorza or HB cup.
Bottom right is the vorza cup.
sorry the Kyosho spur is in the kyosho lent to a friend.


Image


Same as above items but photo taken outside (sorry the items are rearranged, but clear as to what is what.

Image

Image

On my savage its the Vorza spur on a HPI diff cup. They also match. Used the alum cup as I have previously melted the plastic cup. Due to the gear ratios, the Center diff rotates faster than the front and rear and hence heats up more.

Image
[color=blue]Regards
RCS2022[/color]
[color=blue][i][url=http://www.savage-central.com/modules.php?name=Forums&file=viewtopic&t=93732]Savage Flux XL; Mamba XL2; 1717; Custom CD; Mech Brakes[/url][/i][/color]

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