Introduction: Resin Casting Gears for Power Wheels

Picture of Resin Casting Gears for Power Wheels

This is my very first instructable and I hope you will enjoy it.

Please any mistakes caused by my bad english. :-)

Some of you will ask me the question, why not just buy a ready to go gear from the shop or ebay for the usual $19,95. You don't need to ask me that, as I have produced these gears as POC for myself to know if it works this way and if I am able to it. Maybe some tim will come and I will need the procedure to make some gears quick and will not be able to buy any replacement parts. Also remember, these parts are much stronger than that you can get in your store.

Step 1: 1. What Do We Need for the Mould Mixture

Picture of 1. What Do We Need for the Mould Mixture

For the first step we will need any silicone fill, but not the one you use for the bath works.

For the first step I have used "Creato RTV/NV" available almost everywhere, but quite expensive. It is about 30€/kg.

It is simple to use. Just take a smaller sample form, put it on the scale and set tara. Keep a piece of paper between the scale and the form as the Creato components and not easy to be taken off any surface.

Once done, fill the RTV (the white silicon rubber) into the form filling it at about 80%. The wight you can read at your scale is now 96-98% of your mixture. The missing 2-4% will need to be filled by the hardener (NV).

Once you're done having the 100% mould mixture, mix it for about 10 Minutes to be sure having a constantly deployed the hardener.

Step 2: 2. Preparing the Gears to Be Copied

Picture of 2. Preparing the Gears to Be Copied

ok. The silicon mixture is ready and now the gears, which are not damaged need to be cleaned ( I have used a usual industrial cleaner). Afterwards a simple electronics contact cleaner "Kontakt 60" can bee used to prevent any resting of silicon an plastic gears. I know there are those very special chemicals, but the $3,99 spray works like a charm. Use it only as much as you can see the gears being wet. than put them with the bigger site to the bottom. That's it!

Now the tricky part. Spray the cleaner on the surface of your mould.

For the smaller gear I've used the "Ferrero Rocher Chocolates - 16Pcs" Box.

For the bigger one a 50 DVD spindle is the best choice, but wasting more silicon! It is up to you.

The tricky part of this step is to keep the silicon at even surface, preventing uneven moulds. This will cause difficulties on creation or resin forms later on.

Step 3: 3. Silicon - Cosmetics After 24-36h

Picture of 3. Silicon - Cosmetics After 24-36h

After 3 days I took a look at the forms. It looks like it is better to keep it in a warm place. MY work bench was too cold and I moved them to another room. The result was a finished form after 12h. You can just touch the surface after 24h and it should feel like,... a piece of hard silicon.

Remove the forming gear (i was using the contact 60) and once it is out, remove the silicon form out of the plastic form.

Once done, turn the form upside-down and prepare the surface cutting any faulty fillings. This Step is very important. However, it only works this way as the biggest part has to be at the top. You will want to be able to pull it out afterwards.

Ok, here is my favorite: Use the contact-60 to prepare the surface for filling with resin. ;-)

Step 4: 4. Preparing the Epoxy Resin and Filling the Form

Picture of 4. Preparing the Epoxy Resin and Filling the Form

Somewhere, I really do not remember where, but it was mentioned in any blog to use metal powder or smaller parts to make larger resin fillings stronger and quick force resistant.

I did take some of those Metal parts from my work bench and mixed it with the resin.

Oh, yes the resin is the "L" with 2:1 given mix proportion requirement. It needs about 5h to begin to get hard.

You will ask me, why not to take the 3 or 5 minute version. It is very simple to answer those questions. : It would get too hot and break by itself, or get burned or get unstable. This is the right component to create a stable gear.

Once you have a form filled with 2pcs of resin and 1pcs of hardener, put the metal powder into it and begin to mix it together. You don't need to hurry. 5 hours is a long time. I have spent 5 Minutes on mixing all together until the resin did not look like two different fluids being mixed, but like one constant fluid with metal dirt.

After filling about 80% of the form you have to start to put some attention to the surface and look if it is still even.Fill more and more of the resin and look at the leveling. When everything is ok, than put more resin than needed and it will be a little bit less once dried. It should not be more than 1%, but maybe you will be missing it like I did. Try to prevent it as it is simpler to polish the surface, until You have the exact height, than trying to put more resin after 2-3 days and expect the "sandwiched" resin will last like it was a one piece construction .

Step 5: 5. Pulling Out the Gears, Cleaning, Polishing

Picture of 5. Pulling Out the Gears, Cleaning, Polishing

My favorite KONTAKT-60 has been used to pull out the gears out of silicon preventing any damage in the white mass. The cleaning has been done with the usual industrial cleaner. The polishing was easy. I used all my existing wood tools for that purpose.

Step 6: 6. the Result

Picture of 6. the Result

the very final and funny step was to compare the original gearbox and the refurbished one. Of course the original one was very quite due to soft plastic. I suppose, the this is the reason for building such devices will need to be tough. My rebuild would last a lot but maybe when getting broken, it would just destroy both new gears directly.

We will see. The test with 18V on both gear boxes in parallel was ok for a 10 Minutes run without any resistance on the wheels. For now it is very stable built and holding the gear by myself did not stop tu make the turns and went forward forcing the turns to slip through my hand easily.

Please let me know if also you have been able to rebuild any gears using this method.


oxbox74 (author)2017-09-15

Hi, is it possible to some advice about casting a mould my dad wants to try and recast this (please see attached picture) but with the heads of the cog so worn down will he be able to make a cast?

Many thanks.

realjohnnybravo (author)oxbox742017-09-15

Hi there oxbox,
good question! I would proceed like this : Prepare all for the silicon and put the broken gear like described above. Let the silicon be hard, take out the gear and then cut out the silicon part at the place, where the gear had the missing heads. Perform the cut along the maximum radius of the heads which are still not broken. Just like a circle along the maximum radius of the heads. Afterward go for filling with resin and hardening and now a tricky part.
There will be a note of the vendor of the resin you will use pointing to the time, when the resin ist still good for any forming after casting, before it gets really hard. It is like "after 3h it is easy to cut and after 5h it is hard enough and really hard". It would than be possible to take it out of the silicon after 3h and cut the heads in to it.
What I did is to cut with a knife the heads and test the gearing. When it was not enough or uneven, than I used a small drill to do the cosmetics, until it worked fine. It took me some 3 hours until I was happy with it.

I hope it helps.
Please let me know how your little project is progressing and if you were successful.
I wish you the best!

nramirez10 (author)2016-11-14

glad i ran into this this. my daughters hummer stripped the smallest gear that makes contact with thhe motor now i can repair it!

bgipson1 (author)2014-05-24

thank you you explained tare much clearer than I did how is the gear holding up? well I hope

robi_ncc (author)2014-05-20

Sir, I want to make gears, so can you give me formulas to make it?

realjohnnybravo (author)robi_ncc2014-05-20

Hi robi_ncc, the exact formulas can be found in the package if the components and I took it exactly like mentioned by the vendor. The only difference was the metal powder and temperature. I kept the part hardening in a temperature about 20 degrees Celsius for about 24-48h, which the first was for the smaller gear and the second for the bigger one. Afterwards, I took the parts into about 25 degrees for a day.
I hope it helps.
Many thanks for your comments!

robi_ncc (author)realjohnnybravo2014-05-21

Thanks for reply sir, can i get the gear making formulas from you please?

realjohnnybravo (author)robi_ncc2014-05-24

Hi there robi_ncc. To be honest, I used the formulas given by the vendor. For the mold it was something about 6/100 and for the resin 50/100. But it always depends on the products use use. For the powder it was less than 20g for both gears mixed up with the mixed up resin and hardener mixture. The most important part of the procedure was to wait 30 minutes and remix the powder - resin solution, otherwise the metal goes too much to the bottom. The gears I have made were not perfekt, as you can see on the pictures, bit for the next time I would try to wait another 30 Minutes and afterwards try to fill the mold. We will see.

Thanks for your comments!

robi_ncc (author)realjohnnybravo2014-05-24

sir, what was the formula given by the vender? I forever grateful to you.

Edgar (author)2014-05-20

One happy kid!

Gizmo makers are natural Toy Makers...

realjohnnybravo (author)Edgar2014-05-21

Yep! You are so right!
Thanks for the comments!

Edgar (author)realjohnnybravo2014-05-21

Then, you will love this one, by another Gizmo Maker, a 1/5 Sherman Tank, made of wood, for anyone to make:

realjohnnybravo (author)Edgar2014-05-24

Edgar, this is amazing! I just went through your blog and all mentioned sourced given by your URLs in the blog. Some of them has been bookmarked. ;-) My son is now 6y old and I think about to spent some time and money to build and custom a kids quad next year. I was thinking about a 4WD, but those are mostly built for adults. I did not find any solution for kids so far. Maybe a good frame and additional front drive will be the solution next year. ;-)

Many Thanks for your comments!

Edgar (author)realjohnnybravo2014-05-24

My pleasure, to divulge these things. :)

Well, I don't know about quads, but this is a 3 wheeled Project, that can be added a 4th wheel, and a differential gear train for it:

grapenut (author)2014-05-24

Very nice. Thank you for sharing. Did you use a sharp razor knife to trim the mould?

Bill WW (author)2014-05-19

Good work on your first Intructable.

You said "why not just buy a ready to go gear from the shop or ebay for the usual $19,95."

This site is all about designing/building things. As someone said, spending 8 hours building rather than spending $8 buying. You did great describing the design/build process.

jhprouty (author)Bill WW2014-05-20

Johnny - great instructable, I'm thinking about applications as I write this. And Bill, you hit the nail on the head - it isn't about the object, its the process of getting there. I'm new to all this and having fun - though my wife wonders why I don't just find it on line sometimes!

realjohnnybravo (author)jhprouty2014-05-24

Thanks jhprouty! Do it and please let me know if the instructions worked for you. I really like the instructables page as You can share so many information about your smaller and larger projects including electronics, cooking, woodwork and e.g. making cakes! :-)

realjohnnybravo (author)Bill WW2014-05-19

Thanks very much! That's the point!

agis68 (author)2014-05-20

very useful instructable thanks I will try it to make a gear and replace my scanner's broken gear.....

realjohnnybravo (author)agis682014-05-24

Thanks agis, I hope this instructable will help you. Please let me know when succeeded!

lourens01 (author)2014-05-20

I find the intro and comments most interesting. The fact that we appreciate the accomplishment of the efford far more than the economic viability is fantastic. Great job this is exactly why I spend hours on this site. Thank you, great job.

Thank You Sir!

sopansbs (author)2014-05-20

Thank you so much for this wonderful and stimulating idea. Extremely enjoyable instructable, and without even beginning to make it!

As for the application, I just had a flash. It might be a terrible waste of the transmission ability of these gears, but I think they would fit right in for making hand-cranked steampunk moving mechanisms in softwood furniture?

Let's say one needs a 6-inch od pinion for which a sample metal pinion is available. But large metal gears would be too unnecessarily heavy, especially since there is no need at all for that high a transmission capacity.

Makes sense or am I looking at it the wrong way?

realjohnnybravo (author)sopansbs2014-05-24

Hi there sopansbs. The steampunk sounds good, but moving a 20kg kids quad with an 25kg boy on it on the 5% hill climb (5m height on 100m length) will destroy any wood or soft gear. The batteries get over 40°C and motors get untouchable hot at the top. But hey! When I was you, I would just try it out! It just depends on the size of the gears. It is just the question of size. The Egyptians had only the wood and stone to build the pyramids and we are still trying to explain how. Right? ;-)

Andsetinn (author)2014-05-20

Nice write-up.

I read an a russian blog some years ago where he was casting gears, using 2 part epoxy as resin and clay as mold. Using clay gave him the opportunity to remove a gear with missing teeth, rotate it and press it carefully into the clay again, thereby creating perfect mold to cast replacements for broken gears. Oh, how I miss those early days of Goggle translate. :)

Hi there Andsetinn. Maybe I stepped over any of those blogs. I do not remember exactly what I found where, but the main idea came out when I was reading about the carbon fiber + resin stability with further alternatives to make the constructions more stable and unbreakable like for car parts or gears. There are many studies out there about different technologies applied to production processes matching the requirements. Long story short, I did look for the components needed and found them directly nearby. Another day, my son broke the gears and the story behind this instruct able began...

Many Thanks for your attention and comments!

lloydrmc (author)2014-05-20

Nice job, especially considering that it's your first effort.

Don't sweat your English. I find your exotic syntax and usage to be quite charming.

realjohnnybravo (author)lloydrmc2014-05-24

Thanks a lot lloydrmc! Many Thanks for your comments as well.

rspellicer (author)2014-05-20

Nice :) What type and proportion of metal powder did you use?

Hi there rspelliecer. I took about 20g for the whole mix. It was about 300ml mixture. I hope it helps & Many Thanks for your comments!

karlpinturr (author)2014-05-20

A great idea - and one that I'm sure I'll use in the future.

I have just one question: Did you buy replacement gears and decide to resin-cast them, or did you get them some other way?

Your English is better than my attempts at your native language would probably be, but I'm not sure I quite understand when you say "and set tara" at the end of the first line in the third paragraph of Step 1: Do you mean 'etcetera' (which means 'and other similar things' or 'and so on'), or did you have some other meaning?

bgipson1 (author)karlpinturr2014-05-20

I believe He meant TARE which means subtracting the weight of your mixing or measure container from the ingredients most new electronic scales have this feature ,place empty container on scale push the TARE button then place ingredients in container

realjohnnybravo (author)bgipson12014-05-24

Sorry guys. I live in Germany and such a mistake came from just reading the description below the button. Now you know what is meant with tare/tara. Once again: Sorry about the mistake.

karlpinturr (author)bgipson12014-05-20

Sounds more logical, thanks (mind you, I've only ever heard of 'Tare' in fishing-bait terms, so would probably have had to ask anyway!).

Many Thanks karlpintur!
I did not buy any new gear. The power wheel has exactly the same gearbox on both sides and only one side was broken. So I took the unbroken gear box apart and did a copy of the two gears for the damaged side.
Setting Tara is what we say when setting the weight to zero whereby a cup is already giving a weight on the display. This say you can measure the weight of the content excluding the cup. You put a plastic cup which weight is 60g and set Tara to zero. You put resin into the cup until you see 120g on the display. This way you have the weight of the resin only.
Etc means exactly what you supposed it would mean: et cetera. Here ist was a place holder for anything of your choice. I did only use what has been described in this instructable.
Once again: Many Thanks for your comment!

Thank you realjohnnybravo - I hadn't registered that there are 2 gearboxes (I'll have to read more carefully in future).

What you describe as "Setting Tara" I've only previously heard (in UK English) as 'zeroing', so have learnt at least 3 things from this 'ible!

DragonfireFX (author)2014-05-20

what you may want to try on the next set of gears you make is to angle the teeth in like transmition gears like these

Hi there DragonfrieFX,
Good idea indeed, but the described method is only usefull for exact copies of an existing gear. Such angles I would need to 3D scan the existing gear and redesign it with further printing them maybe. I do not know if PLA would last good enough as resins. However, it's a very good idea! Many Thanks for your comment!

Both pla and abs would not hold up like the ressin due to the layering of the printer. I would also avoid the scanner, they still have a high amount of problems and are not the most accurate tools. I would do a entire drawing with calipers and add the angle. The print in abs so you can smooth the parts with amonia vapor to give them the look of injection molded, and then resin cast from there.

Got it. I guess, when trying out my proposed solution I would just have to create an "Failed Instructable" to prevent people going through the same mistake. Thanks for sharing your knowledge about it. It is great to know, that there are people with such experience. All the best!

We have production pieces done in house by having them sent off for SLS printing, which are then coated with a thin primer, and then resin cast. We use and for our printing, the latter being cheaper, teh former being much faster.

There are many free gear generators and herringbone gears availible in differnt rates on thingiverse, so the engineering would be light if you have decent 3d printer software.

Hi there AzzysDesignWorks, I already knew about the Solidconcepts and Shapeways being mentioned in any magazine or gadgetery website. It is a very good solution when going forward with any production of precise pieces or gears. My intension was to try out the possibility of just copying a gears with the cheapest tools just like anyone could do.

For any special own development I would go for a solution like this as not having any 3D printer with such possibilities and a way to develop a 3D model and let the pros build it for you is the best way you can go for it.

Many Thanks for your comment and reference!

dpatterson13 (author)2014-05-20

Excellent!!! I have similar interest in plastics for gears. This method will work perfectly in most low rpm settings where balance doesn't really come into play (my main interest is in building gadgets to entertain children, rides, games of skill, etc. This opens a great big door, thanks!
I wonder if how much magnetic motion would be required to keep the metal suspended?

Learning about resin is sort of like using "JB WELD": learning what CAN BE successfully accomplished by its use far outweighs dwelling upon it's limits.

if you are willing to risk discovering something, you can.

Hi there patterson13,
These are great words! Also a very good idea regarding the magnetic brake! I guess it does not have enough metal in it to perform any usefull brake function. How about dipping neodymium magnets into the gear? Any thinner magnets places in to the bigger gear would not hurt much. I guess this one would work. On the outside I would place stronger electromagnets. It could that work as an generator and when placed a proper current on the e-magnets it would be able to brake or work like an BLDC Motor. ;-) lots of ideas...
Many Thanks for your comments!

Orngrimm (author)2014-05-20

Thanks a lot for this 'ible! May come in handy soon. :)

Looks you are german or swiss by the looks of your tools and sprays? Where did you buy the Resin to pour the end-parts?

realjohnnybravo (author)Orngrimm2014-05-20

Hi there Orngrimm, I did take the resin from and the other parts was Amazin and yes, I'm a German guy. You got it. ;-)
Many Thanks for your comments!

lloydrmc (author)2014-05-20

Nice job, especially considering that it's your first effort.

Don't sweat your English. I find your exotic syntax and usage to be quite charming.

_soapy_ (author)2014-05-19

I notice the comment about 18V. I assume you did as I have and voltage boosted the car?

I only pushed from 6V sealed lead acid battery to 7.2V lithium ion. I have wondered how far I can push it. What voltage was yours at the start?

realjohnnybravo (author)_soapy_2014-05-20

This is a good question. I've checked the motors and figured out, that those high torque motors are used for the voltage range of 6-24V depending on usage area and thermal condition and cooling. As the car has an physical overload switch set for about 120W it was an just a try and error game to see, that the switch reacts very fast when running at 24V but not so quick at 18V. My son takes the ride to the woods with an 12 and 6 Volt connected in series. The overload switch reacts on higher hills but it does not matter. We just have to wait some 20 sec. and the ride is again ready to run. The motors will get quite hot but those are covered inside of the car not being able to hurt my son. Fine. However I will upgrade this small toy to 24V with a regulated power supply, when having more time to play with it.
Many thanks for your comments!

About This Instructable




Bio: tons of prototypes, lots of proof of concepts and the final version is something completely different part of the story.
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