AISI 1025 for Final output Transmission Shaft

T

tsull

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I'm just plunging into my first lathe project (HF 7x10) which is to turn new shafts for a RC Tank transmission. The tank is a King Tiger with a 480 can motor (per side) running on 7.1 v with a reinforced step down transmission (per side).

The gears and shafts are some type of hardened brass (I'm just learning the different types of metals/lol) in a steel transmission frame. The final output shaft has the final gear and two collars. The hex screws were drilled too deep into the final shaft and it snapped.

My first project is to replace the shafts with a harder material. In researching what is the best material for transmission output shafts, I ran across a very lengthy article on shaft stresses, materials and what would constitute the best material.

The research paper indicated that AISI 1025 steel was the best material to use for a transmission output shaft (so, why did the manufacturer use some type of brass alloy for the shafts which are known to break???).

Does anyone have experience using this material for small transmission shafts and, more importantly, can I (absolute novice!!!) turn the material on a small HF 7x10 lathe?

Can you recommend a vendor I can buy a small amount from?

Thanks for everyone's help!

TJS
PS: here's a picture of a couple of the RC Tanks that we battle with using an IR Battle system and a picture of the transmission shaft that snapped and how deep the stop collar hex screw was drilled into the actual shaft itself. Although these are aftermaket transmission shafts, they continually snap according to other tankers (our hobby lingo/lol).

image.jpgimage.jpg

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Those are pretty neat! Now this could be a dumb question, but are those made to be the weak point? Easier to replace then something else in the transmission? The reason I ask is if you make that out of a harder material, what will be the next weakest link?

Chris

edit: when making the shaft could you make it out the same material and just not drill as deep?
 
Thanks for the response! I was thinking about that, but the system is fused. If the metal tank treads lock up with a stone or something, the fuse will typically blow.

It's difficult to find/buy replacement shafts from the manufacturer and I've heard that the transmissions have a tendency to break the gears which are some type of brass alloy.

I'm hoping to develop enough skills and equipment to design my own heavy duty transmissions for this application. There's several manufacturers, but 2 out of the 3 have known issues. The third is brand new to the market and looks very heavy duty.

I was going to order some aisi 1018 steel and try that first. I can't seem to locate the aisi 1025 in small quantities.

tjs
 
Nope, they only have 1018 to 1045. But, thanks for the website. I added it to my vendor list.
tjs
 
OldMachinist said:
1018 should work fine for the shaft. It's a little difficult to get a good finish on for a novice and you may want to try one one of the easy to machine grades like 1215 or 12L14. McMaster Carr is a good and fast source for small quanities.

http://www.mcmaster.com/#standard-steel-rods/=kulgdn
Click to expand...


Do you think that there would be any discernible difference in using 1215 versus a 1025 for this type of application?

I'm more concerned with just being able to turn the material cause if it breaks again, I can always turn another one !
tjs
 
There is no such material available in AISI 1025 grade unless you buy a mill run of it. If you bought a mill run of it, the tolerance on chemistry would range from about 1022 to 1030 in grade. You can get AISI 1026 grade in tubing only in selected sizes, but no solidbar.
Get you a piece of 4130-4140/42 cold roll bar or piece of drill rod and make another. Don't use 1018/1020/1026, material unless you are wanting to carburize it after machining a new shaft.
 
Thumbs up on all the information here. I was thinking of suggesting 41xx myself but it occurred to me that the next weakest link in the chain will break. I'd be inclined to figure-out if there's some other issue going on. Maybe yes, maybe no... -and a stronger shaft will do the trick.


4gsr said:
There is no such material available in AISI 1025 grade unless you buy a mill run of it. If you bought a mill run of it, the tolerance on chemistry would range from about 1022 to 1030 in grade. You can get AISI 1026 grade in tubing only in selected sizes, but no solidbar.
Get you a piece of 4130-4140/42 cold roll bar or piece of drill rod and make another. Don't use 1018/1020/1026, material unless you are wanting to carburize it after machining a new shaft.
Click to expand...
 
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