View Full Version : Belt Drive Differential System (BDDS) from TGR

2008.01.20, 04:45 AM
Innovation Spirit

At TGR we always search, think, brainstorm on what we can do to evolve this scene.
Now it comes; The ultimate transmission differential with infinite gear ratio.


Its totally a unique design by TGR. It is belt driven, it is steel, it is small and fluent in action. We've tested this system for several months in our factory test track away from the crowd. For the last several weekends we've started to use it with people who comes to our track. Everybody noticed how quiet does our car go. First they thought about a perfect mesh. But when our car was alone in the track and people started to hear even the servo sound from the car at the end of the straight; secret was over! We've opened the hood and the same question arised


Most highend racers are aware that 130 sized motors' timing are reverse reatarted. This is due to mass production of motorcans and hobby usage is really low. Many people observes that their cars go faster and with more punch when it goes reverse. Another symptom of this problem is the AWD's which performs almost the same speeds with 2WDs despite the gear ratio. Since motors used with reversed polarity in AWDs those timing error auto corrects it self.
However we couldn't add more gears to 2WD to correct spinning direction. Solution is simple. Using a belt instead of gears results in a correct direction spin for the motor, regarding its timing.

Since it has no teeths but has wheels, all you have to do is to adjust your pinion or spur radius. Just you name it. You need a pinion with 3mm radius or 2,5. Ah you need a little more punch? Then how about 2.225 or would you prefer 2.1234? You can even create your very own and secret pinion for your motors' or track's need.

All differentials on the market has D cut or even worse O cut pressure plates to transfer the action. We thought if we use hardened steel as the caps and we can get rid of large heavy pressureplates. It is even harder than the common pressure plates which are infact used as washers in the industry. Moreover it is lighter than conventional cap+pressure plate combination.



Most racers like the idea of tuning of the diffs from the outer nut. However many diffs on the market has problems when you need a realy tight differential. Due to ball size versus ballbearing cage thickness issue, you can not over tighten most differentials. Solution to this was also simple. With the cost of extra machining we've moved the ball bearing just a little into pressure cap. Here it goes. A differential which is really adjusted and adjustment is from the outer nut.

All those reasons led us to this unique innovative design.


Now lets take a look at other features of TGR Belt Driven Differential System (BDDS)

Steel shaft, caps, wheel adapter.
Hear treated extra hardened pressure caps
Extra Lightened 8 Ball Spur

2008.01.20, 05:25 AM
Wolf, that is simply amazing. Hopefully those motors will arrive before you guys head to the toy fair. I imagine that thing is going to make quite the showing with that new belt drive system...

2008.01.20, 07:42 AM
Yes this is smart! I want one! So will they fit with just a normal MR-02 ir do you have to have a TGR?

2008.01.20, 08:01 AM
It fits to MR02 also

2008.01.20, 08:48 AM
the wonders never cease:eek:
i need to get my hands on one!!!!

2008.01.20, 09:31 AM
i'd really like to see one of these in action myself.

2008.01.20, 09:51 AM
Fantastic work to the TGR crew. I'm really looking forward to this!


2008.01.20, 10:26 AM
Don't you have to run the motor in reverse?

most motors are designed to go one way......the timing only works one way. So if you run it in reverse the timing is wrong.

It looks like you have no diff action at all. So this is a straight axle?

2008.01.20, 01:36 PM
the diff rings are built in to the outdrives,8 balls,and the thrust bearings are sunk in:)

the timing works both ways,90% of factory built motors ive looked at are approx 5deg retarded

2008.01.20, 11:34 PM
Thanks for all comments, questions and feedbacks.

Main question is do we have to run the motor in reverse?
Yes. As Matt already pointed 90% (infact I haven't seen opposite yet) of the motors on the market have retarted timing. Where as we prefer to have advanced timing for modified races. I guess this is due to mass production of the cans and regular uses of 130 size motors in the industry. And since hobby usage is relatively too small we are faced with this situation. What we are stating here is, motors with retarted timing will perform better if you use them in reverse. And we've given simple indicators of it in our introduction message.

Another question is about diff action. Spur, pressure plates and shaft pictures are above. Pressure plates are also diff cap or outdrive in this design. They are heat treated to get get extreme toughness. Moreover pressureplate which is close to the motor locks to shaft with extreme tight fit. Whereas the outer one with wheel adapter has free spin over shaft. Just like any regular diff. However this design is too compact that, I can understand assembled photos looks like it is a solid axle. But it is definately not.

We'll have some more new and innovative products which will be announced ver soon.

2008.01.21, 12:15 AM
That's a fantastic idea and I'd love to get my hands on one. However, I naturally assume that there would be quite a few flaws such as...

What about the belt coming off the motor pinion?
What about snappage?
What about slipping in more powerful motors?

Unless you've already dealt with them.

2008.01.21, 12:55 AM
I assume those issues can be dealt with by upping the belt tension. But then I am worried about belt tension changing nearly every run if this system uses tension and not teeth to transfer power. :confused:

I think it's a great idea, but I would really, really like to see a toothed belt. IMO it would do wonders for reliability and probably improve the rolling resistance as well since you don't need to use any belt tension at all -- let the teeth do the work. :)

2008.01.21, 05:13 AM
Due to my poor english; either your first and second questions are the same or the second and third. Can you explain the snappage?

By the way, we've already tried many motors including chili, anima etc without any problem.

As you know even toothed belts has a part called "belt tensioner". Moreover when teets involved you ar again limited to certain amount of teeth count; as a result limited gear ratio alternative. Especially thinking about the small area we have, we'll defintely have many small amount of pinions and spurs if we use toothed belts.

2008.01.21, 08:01 AM
I was wondering about if the belt comes off?? Like if you hit something for example?

Davey G
2008.01.21, 08:40 AM
Hi Wolf,

Its nice to see your company coming up with cool ideas for these little cars. I have 2 questions though. Have you tested the amp draw (efficiency) of your belt drive verse gear drive? I would have to assume that the belt will less efficient, meaning it will draw more amperage due to having constant pressure against the belt. My other question isnt direct towards you directly WOLF, but really to the MINI Z industry. If what your saying is fact that the motors timing is retarded, why hasnt anyone stepped up and made a motor pod that mounts the motor on the opposite side of the car???

2008.01.21, 09:10 AM
I have tried a few 2wd belt driven cars in my day and never have
they been more efficient or faster. If it was then you would see
all 10th and 12th scale direct drive cars with belt driven systems.

the pressure needed to keep the belt from slipping took power away
from the motor. For the Rc10 i tried the trackmaster belt transmission and the
hyperdrive belt system. Also a direct drive 2wd car. I can't remember the name.

Now that all said. Maybe the mini-z cars are light enough not to worry about slip and power loss but I'm not sure about that.

Dave G, PN does have a motor pod out on the other side but that is for the nascar mini-z and to run oval.

2008.01.21, 09:38 AM
wcrotty beat me to it, but PN makes a mount that looks like it can be run in 102mm and 98mm

2008.01.21, 01:03 PM
I have tried a few 2wd belt driven cars in my day and never have
they been more efficient or faster. If it was then you would see
all 10th and 12th scale direct drive cars with belt driven systems.

the pressure needed to keep the belt from slipping took power away
from the motor. For the Rc10 i tried the trackmaster belt transmission and the
hyperdrive belt system. Also a direct drive 2wd car. I can't remember the name.

Now that all said. Maybe the mini-z cars are light enough not to worry about slip and power loss but I'm not sure about that.

Dave G, PN does have a motor pod out on the other side but that is for the nascar mini-z and to run oval.Not only that, this is not a toothed belt, but a friction o-ring system that would require significantly more belt tension to prevent slipping. Neat idea though. I'd like to see one up close before commenting too much about it.

PN makes a "reverse" pod for the NASCAR series. These might actually make a good mount option for the upcoming LM cars. There would be an issue of legality in running an advanced timed motor in a organized race setting. I guess that means that the motor manus will have get on the ball about correcting the timing issue. :D

2008.01.21, 01:30 PM
Too many comments to handle and I have too many new products to announce and make them ready by the end of this month. So, please excuse my short or too direct responses.

Since cris works for you at the moment, be sure that you'll test one of these if you and cris has time for it. Meanwhile I couldn't get the point why we should need extra tension due to friction damper. And please note that this not a O-ring but its belt just like the ones in the casette players

Our cars are really light in weight (150-160gr), torque of the motors are not comparable to 540 size motors. So we thought that belt would be sufficient to hold this car without any slipping. And we've seen this after the tests we had

I don't know why others haven't done this yet but sometimes very simple ideas might be missed by many people.
About amper draw; It will not be a fair test. A motor withan advance timing will try to draw more current and will become more efficient and will produce more rpm regardless of the transmission. What observed so far more fluent car in and out of corners and your finger on the throttle is just like attached to the car. We had more rpms and more topend speed with the same ratios in the expense of a little decrease in runtime but this is negligible regarding current race times.

Belt sits in a slot both in pinion and spur. We haven't had getting off the wheel experience despite too many accidents and crashes (some intenionally, some of them not :) )

Yes if you overpull the motor, belt will create too much tension which might create negative issues. But with the current inertia of the car a small static tension is enough to create necessary tension on the belt.

Now my question is why nobody comments on the alternatives that we might have on gear ratios? Or how light this diff can be with lighter materials?

2008.01.21, 01:37 PM
Sorry for the misunderstading. I got your point now. But my comment about o-ring versus belt stays. We've also tried this with o-ring and you are right. We would need extra tension with a rubber or silicone o-ring. Thats why we opted for drive belts instead of o-rings

2008.01.21, 04:21 PM
Now my question is why nobody comments on the alternatives that we might have on gear ratios? Or how light this diff can be with lighter materials?
Well, my comment about tension remains standing. A toothed belt is always run loose, this significantly reduces the amount of drag in the transmission. I'm pretty sure your customers would have more peace of mind too, knowing that the belt will not slip should some oil get into the system (as is often the case for greased ball diffs).

Regarding the weight of the diff: It looks light as is (care to put it on a gram scale for us?), but I'm pretty darn sure you can make it even lighter if you use Delrin hubs and mill some thin pressure plates. ;)

2008.01.21, 04:53 PM
I believe Wolf that there is no issue with the belt slipping or coming off. And I'm sure that it's not too tough to figure out if you have enough tension (or too much).

Think of how belt systems work in cars that drive water pumps, AC, power steering, etc. They are just sitting in a grooved pulley. Much greater forces are at play in a car.

When will this be ready for the rest of us?
What would the cost be?
How will you sell the pulleys? Just in sets for the motor pinion? Or different differential pulleys as well?

Very cool idea guys, I look forward to seeing one in person.

2008.01.21, 11:50 PM
WOW, great idea! Now the awd need a kit:D -mike

2008.01.22, 12:08 AM
We have limited stock for this item at the moment. First batch of mass production will be ready around mid february. It will be sold as the other differentials on the market. ie some pinions will also be included in the differential set. Of course there will be replacement and optional pulley both for the diff and motor. Total differential set price will be around again regular differentials. We have some extra unit cost due to CNC machined spur and pinion but we'll try to compansate this.

As for the weight there are many more reason why it is lighter in design. For example; extra lightened spur, smaller balbearing (3x6 instead of 3x7) etc. I'll weight it whenever I have time for that.

As rharris also pointed out flat belts are capable of transferring higher loads and preffered in many industry applications. Timing belts are for the applications which needs exact timing synch for the shafts or belt size is not enough to carry required torque (like 1/10 scale cars.) Moreover timing belt was out of question in our design phase due to limited gear ratios.

2008.01.22, 02:22 AM
cool idea... waiting and watching... :D
and wondering how much it'll cost... :D
would definitely like to see it installed in another motor pod/mount...
i.e. kyosho stock motor pod (hm, rm, mm); atomic; pn etc... etc...

2008.01.22, 04:50 AM
That's fantastic then. I might have to get me one of those!

2008.01.22, 07:41 AM
Very nice! You Sir, will see the colour of my money :)

2008.01.22, 08:54 PM
I am very impressed with this BDDS and I myself am hoping to be able to purchase one when they become available. :D
But could you please delve more deeply into the data you've uncovered regarding the motor negative-timing issue that you've come across Wolf? How is it you tell that 90% of the motors you've come across are negatively-timed for Mini-Z use (For Forward throttle-position) instead of being neutral in timing or advanced-timed for Forward throttle position? Also, what about in the case of Atomic's new Evolution Series motors the STOCK-R and the CHILI? I have heard (Not for an absolute fact) that the new Atomic M1 brush design is specifically designed for optimum (Advanced) timing for Mini-Z usage (Forward throttle). Have you tested the timing on these two motors?
Thank you for your help with this :D

2008.01.22, 09:34 PM
the m1 brushes have more of a wrap around the comm,changing the timing and producing more torque from the increased surface area.
the thing that bothered me with the old design is,as the brushes wear the timing changes quite a bit,especially if the endbell isnt fitted straight.

stock motors and machine wound vary + or - 5deg on average,ive seen some as much as -10deg!!

i have 2 stock r's on my to play with list.ill check the timing on them soon:)

2008.02.25, 06:07 AM

how did it go with the timing check of the stock-r??

2008.02.25, 01:04 PM
I was building some motors a while back, and came up with several very fast motors. I thought I was correct, but this confirms it. I had 2 motors that stood out above the rest, far and beyond. I even had another guy building motors, trying to build a faster motor that was "stock board" safe. We are running the old 3004 boards. I used the PN ball bearing motor can. An armature out of an X-Speed motor. Magnets out of an X-Mod stage 2 motor. I accidentally put the magnets in backwards. And it didnt click untill he asked me "Why are your motor wires backwards?" Hope this helps some guys out there build some faster motors. ;)

2008.04.03, 11:33 PM
we got the belt drive system for a bit of a test:D


so far its looking really good,ive run it in my AD mr-02 with stock r,you cant hear the car at all:eek:
it feels plenty different to a gear diff,kind of driving a turbo 1/1 car.
the actual diff action is very smooth,i havent had the chance to sand the bearing surfaces down just yet,all the adjustment is in the side nut making it ver easy to tune
more pics soon......

2008.04.04, 12:04 AM
Any chance you can post a a quick video for us Matt?? I think I speak for a few of us when I say I've been looking forward to this. :)

2008.04.04, 12:22 AM
im on it:D
as soon as i can get up to nobby's attic with it,probably do the open car first as the sinister is having a little bit of work done;)

2008.04.04, 01:32 AM
This is OT but

I see you are running a "normal" damper spring plate system there....
are you using all the parts post and both springs?

And have you mad ethe hole in the carbon piece from the motor pod bigger??

I also have the BDDS but it is not mounted I am waiting for replacement parts after craching my sinister in HURDA in Jonkoping last weekend... :(

you are even running the newest toplid!! Is it working can it hold the batteries in place? Even wiht a stronger motor like the chili??

and what if you run into things can it still hold the batteries in place?? And were did you get it? directly from TGR?

2008.04.04, 01:42 AM
I see you are running a "normal" damper spring plate system there....
are you using all the parts post and both springs?

And have you mad ethe hole in the carbon piece from the motor pod bigger??

yup still experimenting with an rcp setup:)
its got blue atm disc damper springs, .8mm side plates,.5 castor/1 camber top brace,kyosho yellow front springs/atm spring mounts and tgr wide rear/30deg atm aw fronts(im thinking slick r though)

just machining up some bigger pinions;)

the new top plate works,no problems so far

2008.04.04, 03:05 AM
let us know how it turns out! If it turns out good maybe we all could get some pinions from you!? :)

Are you running without the rear springs?

For the race last weekend I had the sinister black on one side and an orange ATM spring onthe other side (to get rid of tweak)

2008.04.04, 03:51 AM
i have the black springs fitted for now(need to test)as the tgr damper holds it up on its own.

the pinions look good so far,i have one on my mod mr-02 right now:D

2008.04.04, 05:14 AM
I'm glad that you are up and running . You should have 3 pinions alread and you still need larger ones? Standart pinions we have are 2.3,2.6 and 3.0mm. Since the diff has 17mm diameter you should have 5.6 ratio already.

As you; said feeling of the car totally changes with BDDS. When I first drive it, it was like using brushless motor first time while racing brushed motors.

I wonder why you switched to plastic plates instead of carbon ones?

I hope you receive your suspension plates soon and let us know what you think about BDDS

2008.04.04, 05:22 AM
wolf i need to catch you on msn;)

just testing things with the plastic dd plates,i need some instructions for the spinner+ too

2008.04.04, 06:27 AM
Here is a link too Spinner+ info on TGR place:

I have an aditional Q? on Spinner: I have the older spinner and when I drive sinister with 9/43 gearing and the atomic chili engine the ESC start shutting down after 5 minutes...

can yuo explain this please? (9/43 is a good gearing for the engine, and the spinner is OK with the chili engine, Betteries = intellect750AAA cells)

2008.04.04, 08:02 AM
thanks for the link,wolf got it on there today:cool:
does your spinner get hot?
ill be testing on carpet tonight and rcp tomorrow,more pics will be in the next few hours:D

2008.04.04, 09:19 AM
just a short one for now but you get the idea,no slipping or belts flying off:D

http://i119.photobucket.com/albums/o130/mk2kompressor/th_sinistersteeringanddrive.jpg (http://s119.photobucket.com/albums/o130/mk2kompressor/?action=view&current=sinistersteeringanddrive.flv)

ill post some pics of the steering setup in the other thread

2008.04.04, 01:44 PM
I wonder how the difference in on-power weight transfer (compared to a pinion/spur based diff) affects handling, MK2... have you tried this on the track yet?

2008.04.04, 02:22 PM
yup,ive had the bdds fitted to my ad 02 the last week or so,on rcp it actually helps me go round corners:D
ill get some pics and a vid of it in action on the 02 soon:)

2009.03.11, 07:15 PM
Now that some time has gone by... how have these belt drives been performing?

Seeing as my MiX now uses a belt drive... I am wondering what problems I may face, other then trying to source a belt the right size...

2009.03.11, 07:41 PM
i get on well with it,you need to fit a small O ring on the pinion to get it to grip the belt but other than that its fine.
very different to having a gear diff though,it forces you to drive smoother:)

2009.03.12, 09:14 AM
Would this diff fit an iwaver motor mount? I think the iwaver system diff is very close to the mini-z system. May someone confirm that, before I bought one at atomic?

Is there any other places that sell this?

Thanks in advance!

2009.03.12, 02:28 PM
they will it any mini-z/iwaver based 2wd motor mount

2009.03.12, 03:30 PM
Has anyone tried Friction Additive to the belts? - a liquid that INCREASES friction with out making it sticky

2009.03.12, 04:07 PM
i havent no,might be worth a go,whats the name of it?

2009.03.12, 04:31 PM
Trying to find out...

I had a business teacher in a class that I dropped, that she mentioned something about owning a company that made something like this... I will be going back and ask her what it was, if I cannot google for it.

I plan on including it in my MiX kit...

2009.03.12, 06:38 PM
they will it any mini-z/iwaver based 2wd motor mount

Thanks dude! :D