Help required

[Momos]

I have a acme racing monster t nitro truck it's 4 wheel drive dif at front and rear with drive shafts running to a gear in the middle I was wanting to fit a 540 motor to this gear the motor I have is out of a clodbuster with standard pinion how can I find out what pinion I need for the motor to run on the acme gear

[kaylon]

Well.. Maybe a bit of deduction to start with.

Assuming it's an Acme from the last few years then it's probably an Himoto oem. Which is the same as Maverick's etc in the UK. Once again assuming that then the Nitro and Electric chassis share many common parts including the drive train. Granted this is not including the center diff. This range of cars though as a rule use Module 0.8 pinions ... I would start by seeing if a 15t Mod 0.8 pinion would mesh well. Doing it by eye first.

Now the prob will be that the center diff spur will probably be a fairly small diameter and I'm not sure how a low tooth count effects the pinion ratio. I guess it's about a 48 tooth spur. There are tables all over the place that help you work out gear ratios .. But from what I know most 48 tooth spur gears run from a 13t to 19t pinions...

Basically across the drive train you want to get as close to 1:1 ratio between the motor turning and your wheels turning. There is math involved to calculate this depending on size of wheels etc and some info can be found here.

If the monster truck has 3.8inch wheels with a 48 tooth Spur using a 15t pinion would give you a 0.4 roll out. Not to bad, would have fair acceleration and not bad top end speed but keep the strain down on the motor. This is all based on the info that 'most' Acme trucks I looked at have a 10.44:1 ratio or about that... so using a 15t pinion on the 48t spur seams to work.

Not sure if any of that is totally accurate but that's were I would start.

K

[Momos]

Wow ok I should have said am fairly new to this I will sift through your information and try make sence of it thank you very much for reply

[kaylon]

Gear ratios is tricky thing. The hardest part though is knowing what type of pinion. 36, 48, 64 pitch.. 0,6, 0.8 module.. to be honest im not sure what is what lol.. but hsp, maverick etc use 0.8, i know thus cos i have a few mavericks. Its still a guess though, but a slightly educated one.

K

[Momos]

So you think I need a 0.8 pinion how many teeth ?

[kaylon]

So you think I need a 0.8 pinion how many teeth ?

15t pinion I recon. (I hope)

K

[Backlash]

Momos,

Can you post a photo of your car so we know what model you are referring to, and also a close-up photo of the spur gear, as we may be able to tell the pitch from the photo..

OH, and does the 540 motor out of the Clodbuster still have the pinion gear fitted? The stock Clodbuster pinion gear should be a 0.8 Metric pitch gear... (13 tooth IIRC)

Edit.. I just Googled Acme Racing and found what your truck looks like.. Unfortunately I could not see a clear picture of the spur gear..

I did confirm that the gear ratio with the Nitro motor is 10.44:1 as Kaylon suspected, although I couldn't confirm what the tooth count was on the spur gear or clutch bell..

Can you count how many teeth the spur gear in the car has, and also how many teeth there are on the clutch bell gear on the Nitro motor..

You do understand that the performance / speed with the 540 motor fitted is going to be a lot less than what you would get with the Nitro motor fitted don't you??

[Backlash]

Basically across the drive train you want to get as close to 1:1 ratio between the motor turning and your wheels turning. There is math involved to calculate this depending on size of wheels etc and some info can be found here.

K

No offence Kaylon,

But this just doesn't sound right to me.... If you were to gear a vehicle with a gear ratio of 1:1, or so the wheels did 1 revolution for every 1 revolution of the motor, then that would mean that IN THEORY with the motor spinning at approx. 12,000 RPM on load (A 540 silvercan motor will free rev to between 14 - 15000 RPM, so 12000 RPM on load was an approximation) the wheels would also be spinning at 12000 RPM and with a 3.8 inch / 96.5 mm diameter tyre, the vehicles top speed would be about 218Km/h..... Now, does that sound right to you... ???? LOL..

I checked what Skraplron has posted on RC Universe, and its just not right..

There has been no allowance made for the motor being used, the battery type or voltage, 2wd or 4wd, or weight of the vehicle.. To state that you would use the same gear ratio when running any motor from a 27 turn silver can down to a 13 turn modified is just ridiculous..

Rollout, is the distance that the vehicle will travel in ONE revolution of the motor for any given wheel/tyre and gear ratio combination... Rollout is a more accurate method of accounting for the vehicles performance than using just the gear ratio alone, as it also accounts for the tyre size, which can also vary between tread patterns and brand..

Rollout is also useful when trying to calculate a gear ratio to gain similar performance/speed between two different vehicle types using the same motor, although consideration still needs to be given to the vehicles size, weight, drive type (e.g. 2wd/4wd), tyre size, and driving surface..

If you want to have a "play" with gear ratio's, tyre size and top speed, there is a good site called Gearchart that you will find useful.. http://www.gearchart.com/index.cfm?fuseaction=chart.create

[kaylon]

No offence taken at all I'm always very unsure about gear ratios

I use the wizard thingie found on that site sometimes and it's worked fair enough so far, I've not burnt out any motors hehe.. it's all based on the rollout of a car.

I was suggesting the 15t pinion based on looking on Nitrotek for an Acme truck and putting in it's details.. 15t gave a 0.4 I think result which looks good to me from what I understand.

LOVE that gearchart link .. that's better then the wizard I've been using

K

[Momos]

The original pinion gear on motor has smaller teeth than spur gear if that makes sense I will count the both gears when home and once again thank yous very much for your help

[Momos]

There is 44 teeth on spur gear and 12 on the bell gear

[Backlash]

Kaylon, do you know for sure the tooth count of the spur and pinion (clutch bell) on his truck?

I agree, it is difficult in trying to determine suitable gear ration, especially on a forum where you cant always know about the vehicle in question, or how or where it will be driven.. I have the added disadvantage that the majority of driving that I've done with RC cars over the last 20-30 years is in a racing environment, where the goal is to gain the most speed from that motor for a 5 or 6 minute period.. If you were to run those ratios in a street / basher car where you just keep driving until the battery goes flat, you would be sure to cook the motor in no time..

Momos, - 10.44:1 does not sound to be an excessive gear ratio for a truck running a 540 silver can motor, so I suggest is that you try a pinion gear that has the same tooth count as the clutch bell on your nitro motor, so that you keep the same 10.44:1 gear ratio with the 540.. The only concern that I have is regarding the weight of the truck, which could be overcome by dropping down one or two teeth on the pinion with the 540....

[Momos]

It's a 12 tooth on bell gear but the problem is that the teeth are thicker on the acme when I run the original gear of clod on acme gear the smaller teeth on clod hits the top of the teeth on the acme maybe am just been a bit silly here but the gears don't run smooth if that makes any sense at all

[Backlash]

LOVE that gearchart link .. that's better then the wizard I've been using

K

Its pretty much designed for RC cars that are used for racing, but if you know the ratio of the cars gearbox, and the size of the spur gear, you can print off gear charts for just about every vehicle on the market..

[Momos]

This is the gears

[Momos]

Tried to upload pic didn't work lol

[kaylon]

Backlash.. Nope I'm just using info gained from surfing the net and looking at info of acme trucks.. Most so far have been 0.8 module pinions with a 48 toothe spur and a 10.44:1 gear ratio so I'm making the assumption this truck is the same as that's all the info given. I have an himoto truggy also which is 0.8 module. Can only guess.. Just trying to give the OP options and create more conversation so he can make the best purchase possible

Are clod busters 0.6 module? they won't be Chucky enough..

K.

[Momos]

Am really interested in all this and I will do my best to keep up could someone explain what the 0.8 is the teeth on acme are fatter if you like than the teeth on clod pinion

[kaylon]

Visual Reference incoming

Here is module 0.8 note the chunky teeth.. and angular top

A Module 0.6 It's a slimmer profile with a narrow gauge and a smoother top ...

And just for further comparison here is a 48 DP pinion. A lot lower profile, still kinda angular but far lower profile teeth. 48dp is bar far the most popular across the board. Mod 1 is 8th scale i think.. 5mm motor shafts.

I'd get a couple and see how they mesh... if you have a nice smooth movement then that's the one ... remember to use a bit of paper between the gears to help get a good mesh, if you can pull the paper from between the gears and it gives a nice crimp and not tear then your in about the right mesh range.. you should have two teeth of both gears in a snug fit and see just a small gap with the adjoining teeth...again just make sure you can move the gears freely and smoothly by hand.

K

[Momos]

The 0.8 and the 48 dp look like what am after

[Momos]

I don't think the motor shaft on clodbuster is 5mm looks smaller than that not sure what size as basically am looking for a 12 tooth 0.8 or a 48 dp 12 tooth that will fit on the clodbuster motor shaft I think lol

[Momos]

I think the shaft size on clod motor is 3.2mm so if am following correctly a 12t 0.8 or 48 dp 12t

[Backlash]

The original pinion gear for the Clodbuster will be 0.8 module.. If the teeth on the Clodbuster Pinion gear are too small to mesh with your trucks spur gear, then it means that your trucks spur gear must be Mod 1?

The only options that you have are to either find a Mod 1 pinion to suit the 1/8 inch (3.175mm) shaft of your motor, or find a 48dp or 32dp/0.8 Mod spur gear that will fit your truck..

HobbyKing may be of help with the pinions, but it looks like they only do a 9T and an 11T pinion..

9 tooth, 3.175mm, M1 http://www.hobbyking.com/hobbyking/store/__45555__9T_3_175mm_M1_Hardened_Steel_Pinion_Gear_1pc_.html

11 tooth, 3.175mm M1 http://www.hobbyking.com/hobbyking/store/__45540__11T_3_175mm_M1_Hardened_Steel_Pinion_Gear_1pc_.html

At that price, I'd buy 1 of each...

[Momos]

Ah that's perfect thank you everyone for your help I have one more question lol I am building a clodbuster as well I have just bought 2 hpi firebolt motors will I run these with original silver can pinions or need to upgrade

[kaylon]

And the answer is.... drum roll....

Mod 1.0!!!

I contacted Acme, very helpful people they use an 8th scale transmission in a 10th truck, that's kinda cool, i guess cos it's a nitro by default

But there you go... the answer is Module 1.0. Just make sure you get the right motor shaft diameter.

K