[dozerbuilder]

Make your own as truckmaker says. I’ve got $800 worth of firgelli's I bought brand new lying in various stages of breakage, stripped gears and a box of broken parts of 6 of them at $75 each and a dealer who totally ignored my complaint, wouldn’t even reply to my email, so we’ve rolled our own. Now we can make any we like in any size and length in our own back yard. It's easy to do and way cheaper than a $75.00 firgellie or other proprietary type. If you can make a model, you can make these. I just finished the prototype for the lift and angle rams on my dozer build. There are many ways to make them and these heavy duty ones work well for me so far. Tilt cylinder and blade lift rams are next. These have a 55mm long stroke. If they were for a Bruder D11, they don’t need to be heavy duty. For heavy steel dozers like my one that weighs 60 lb, they need to be strong and simple in design.


The parts cost for one is as follows, all online from alibaba China:
1 x 100/150rpm GN14 gear motor = $9.80.
1 x ACME shaft 8mm dia, pitch 2, lead 4 =$4.78 for 4x200mm long acme rods including acme nuts.
6 inch length aluminium rail = $0.50
1 x bearing = $0.80
1 x ali tube 25mm O.D dia = $0.50
1 x 12mm O.D ali tube for pistons = $0.10
1 x rose joint 8mm I.D - $2.90

Of course the cost is broken down, I got bulk supplies of everything so I can roll one up anytime I need one from now on.
Now that I’ve made a pair, I could make one in about an hour, with all the parts on hand and access to a lathe to turn the end plugs to the required diameter to take the piston. You can make these any diameter, any piston length and size to fit your needs and they resemble a hydraulic ram. These ones will pull/push 7 lbs each tested on a bag weighing scale at the angle you can see in the pics which is way harder than straight up and down. I’m making a second type now with a larger planetary motor, aiming for 15lb pull. If you were making a bigger machine, the easier it gets since you can use larger dia motors and have more room each end. They are not perfect yet, but I’m nearly there. When I am, I going to make some simple jigs.

Compare these with the commercial ones. These are immensely strong and supported right through on a 16mm ali rail held with 8mm dia steel pins in each end. You can see the split plastic case on the commercial one sitting above the my DYO’s. One rip and the case split open. These are very strong, and the 8mm ACME drive rod is unbreakable in this application. Don’t use a threaded rod, it’s not designed to pull or push – an ACME rod is specifically designed for this purpose and works great. That’s the key to these, the ACME shaft, and choose your pitch and lead to match your motor speed to get the desired piston speed. These are running 8mm stroke per second. The ones I have for the blade run at 16mm per second. About right for 1/16th scale. You can see how that bearing is pounded onto the acme shaft as an interference fit and I have added Loctite. It holds it in place and puts no lateral tension on the motor shaft. It was a bit difficult to make the D in the shaft. I need to perfect that next. The motor shaft needs to “float” in the shaft D. The weakness will show itself soon and if it has one it’ll be the gear motor. I’ll simply make it stronger but they seem to work fine. Soon I will test it down at the closed coal mine ripping and we shall see how they go with 39lb of drawbar pull on them. Then we will know what to improve. Meanwhile, we can roll them up in no time to any size at all.