Let's Make Robots!

My Yellow Drum Machine (in Progress)

Hello all,

 YAYDM, Yet another Yellow Drum Machine!

I have gone away from the original a little bit, my one uses the Tamyia dual gear box and tracks, everything else is machined from Al. It is powered by 6 NiCads and I am using an Ardunio for the brains. I am working on the Sonar now, the drum sticks will be similar to the original but I am using Carbon Fibre rod (because I had some!).

 The suspension is torsion bar and it looks cool running across the work bench over the screw drivers and pliers!

 All the best



Thanks for all the Comments, Yes it is not yellow (at the moment) I will put some Video up soon. I decided to build a YDM because I came across a video of the original on UTube, it was the most entertaining thing I had seen in a long time! Very clever with a great deal of imagination. If people are interested I will tidy up the drawings and post them too.

A little more detail on mine.

The sides are machined from 6mm Al plate, the wheels are turned from 50mm Al Bar  and have Brass bushes inserted.

The final drive is uses ball bearings from RC cars as does the Idler wheels.

The suspension consists of swing arms with steel axles which pivot in brass bushes which are "Locktighted" in to the side plates. The Torsion bars are 1mm Music Wire silver soldered to Brass bolts which bolt on the opposite Hull side plate.

I am building the Sonar at the moment, I cannot make up my mind if I am going to use a PIC to control the transducers or just drive it from the Ardunio.

I am using the same motors for the Drum Sticks as the original.

 //28 Jan 09

 I added a video, enjoy

 Well it's been awhile, lots on to keep me out of  the workshop; anyway I promissed to put some details up and here is the beginning of them, just in case someone wanted to build the same chassis.

This is the hull, it is a 6 mm thick peice of Alum, I used dural of unknown parentage, you need two, I used 6mm to make it thick enough to tap, I milled out two pockets on the inside to reduce the weight but this is not really required, the slot at the front allows the track to be tensioned and the 10.9 mm hole at the rear takes the final drive shafts.


Next comes the main wheels:


These are a simple turning operation from Alum, just put a small radious on the rims, the Tamiya tracks will feed better. Make 6, now Alum is a poor metal for bearing so I pressed brass bushes into the centers, the bush is drawn here:


These are also simple turning exercises, I made a "D" bit to do the final boreing of the centers to get the best surface finish.

The Idler wheels are in the diagram below (right), the Idler is turned out of Alum, it runs on two ball bearings, I use the ones for RC cars, the hole in the middle of the wheel (9mm) is bored to fit the ball bearing, a small ridge is left in the middle to stop the bearing pushing through. The Axle (left) is turned from mild steel, I used 10mm hex bar, the ends (hatched) are tapped M4, I made brass nuts to suit. You need two of each.idler.jpg

These drawings are the start of the suspension componets, in this case the swing arms:


The swing arms are fairly simple, the Swing Arm Pivot is pressed/loctited in from one side and the Main wheel Axle from the other side. The finish on the Pivot and Axle is important, the bearing surfaces should be polished and and a close running fit in the wheel bush and the pivot bush (drawing below).


 The following is the torsion bar end, this is silver soldered to a 0.8mm Spring(Music/Piano) Wire Torsion bar.


 This is what the Swing Arms look like assembled. 


The Torsion Bar is made with a small Z bent or C in the end, the length of the bar is set from the job, the length such the Torsion Bar end hard against the hull as shown and the torsion bar retains the swing arm, it should be such that a small amount of play being allowed. The ride hight is set by turning the Torsion Bar end and then it is locked in place using the Torsion Bar lock nut, this allows the preload to be set. If the suspension is too soft 1.0mm Music Wire can be subsituted.

Final Drives! The gearbox I used is the Tamiya dual motor gearbox, the final drives are carried on two RC Car ball bearings each side. The bearing carriers are made like so:


 A simple turning operation in any metal (make 2), I used brass just because I had some. The 10.9mm hole should be turned a push fit on the bearings you get and the depth to suit the width of the bearing in my case 4mm, the step on the inside should be deep enought to hold the inner bearing in place, the for holes are tapped M2 or similar.


The final drive shafts (2) were turned from mild steel, the axle hole on the inside is drilled to clear the Tamiya Axles, the M2 on top serve to trap the axle. the M2 at the other end (left) holds the Drive sprocket in place. The 1mm pin is to act as a drive pin for the drive sprocket. The hole lot looks like this:-


The only things which remain are mounting bars front, at the rear and the bottom rear for the gear box, i used 6mm and 2mm alum. For the Floor I used 2mm perspex.




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What are you using to control the motors? If it's a DIY borad, could you post some diagrams or instructions? Thanks.

Hi e-square12

I am just using a l293, see http://letsmakerobots.com/node/6328

best regards


So the L293 would be enough for the tamiya dual gearbox? That's strange...I thought gears were a type of load for motors, which would result in a higher Amp draw...oh well. Thanks for answering.

PS: I found a very simple design for PWM and made a mix of Oddbot's relay design. It's pretty much the same controller used for Mr. Basic, but all my components are free (scavenged) and I think mine has more amps... =)

Hi e-square12,

 the L293 seem to work ok, I have fitted a heat sink now, and dropped the motor voltage down to 4.8V; they do get warm.

I drive them using PWM and the video shows motors running at 7.2V (feed to l293) with the PWM running at 35%.

Eletric motors have a sweet spot (RPM) where the power is highest, below that the current will increase, the trick is to match the RPM to the load.

all the best


Where do you stand with this project? Is it done...or what reamins in your to do list? The aluminum parts look great and the suspension too. I would really like to see it finished (drumming, not so much...but it's an amazing development platform).


Hi E-Square12,

 I have put it aside while I do some work on my XMOS Challenge Robot.

Basically the Sonar is running, the drum sticks and motors are done and mounted, I need to build the driver for the drum stick motors. I should put some new photos up.

best regards


Hi Noise0

at the moment the lot is powered by the one 7.2V set of NiCads, I split the supply in to reg and unreg, the motors are driven from the unreg supply.

 I will see how it goes, at the moment i am having no problems the robot drives all the way the the knee in the discharge curve.

I have a bit more electronics to add, I have left room for another battery pack and I have set it up so I can run the reg side from another pack.

best regards from down under

i think that those tamya morots are very noisy

on YDM you have to develop a microphone ampli to sense the sounds...

I challange you to make it working properly when motors are running  under a single batt pack...

I hate a lot to insert a second batt pack  , i am very interested in how to obtain a clean regulated power line even when CC motors works... i have got best results with PI filters using resistor between the caps of the PI... but this lower the max current.


are you planning to power all the electronics with the same battery pack?

Hi Noise0,

 just to let you know, I had a think about your advice and I split the power packs in to a 7.2v 900ma and a 4.8V2400ma pack.

This solves a number of problems, the 7V was too hard on the motors anyway. So I have increased my run time (lots) and cut some noise out, previously I had got most of the bush noise out, but now I don't see it on the 5V rail so that is excellent, just got some small switching transits.

I put Pi filters in also, putting this one aside for awhile I started cutting metal for the XMOS robot; which is my version of the leaf robot, with the code ported to Linux.

 all the best