Dravpnir tries to build something even lighter

[Dravpnir]

This is more or less a continuation of my earlier thread, Dravpnir tries to build something light. But, as I have redesign more or less everything and hardly any part from the old crawler will be transfered I thought it deserved a new thread.

You might think, - "Hey haven't I seen that solution somewhere before?". If you do, you are probably right. I have taken my old design and got a lot of "inspiration" or stolen ideas... from Erik D lux, ClassiCutCustoms, RcBro, EGRESSor and lot of other people.
I do not plan to make more than one or two sets of these parts so I hope these people take it like the old saying, - "Imitation is the best form of flattery" rather than something else

This will be a rather slow build and I do this mostly because I like to learn how to work with different materials and machines. There is also something almost therapeutical with building a home brewed crawler for me, so if it drives well in the end it is a nice bonus

The aim with this project is to build a sub 3 lb crawler. The goal is to have a RTR weight of 1200 g (2.65 lb).

But over to the parts!

Today I got the carbon fibre plates for the gear boxes that Tomy at NCD cut for me. Same awesome work as always with Tomy. The plates are 2.6 mm thick and there will be a 15 mm thick delrin middle part between the plates.

The gears will be the new lightened Berg V3 gears, EBG220.



In order to get the precise thickness I want the delrin pieces to be I cut off a piece of delrin from a 80 mm diameter rod in the lathe and then I will mill the part I want from it. The center hole in the disc is a guide, so I can setup the mill faster.



The axle tubes, atleast for the rear, will be made of alumium and a titanium tube. The titanium tube has a outer diameter of 8 mm and a wall thickness of 0.5 mm. Hopefully these ones will hold much better than my old tries with the thin carbon fibre tube.
The aluminum flange part is only a prototype and some small modifications will be made to the real one. It will also be put into the mill to remove the excess material and drill the mounting holes.

The aluminum is unfortunately only 6082-T6 because I still haven't found any supplier for 7075 aluminum rods of the sizes I want here in Sweden.

I plan on glueing the titanium tube in the aluminum flange with Loctite 648. That is the reason why the outer part of the flange is so long, is to have a larger surface area for the glue. The pocket in the flange is for the flange ball bearing that will stick out through the carbon fibre plates.





That is all for today. Hopefully I will get more time with the lathe tomorrow.

[Beerman Crawler]

I really look forward to watching this build come along, keep up the great work

[ittybitty]

Your builds are always great to watch. Can't wait to see what all you've come up with or are working on for this build

[ClassiCutCustoms]

Looking forward to this...... I am glad I have been able to help you along the process. Your emails are always exciting for me to read. Keep up the exciting work.

[pajey]

Under 3lb. That ain't gonna work...

[Tgreer]

You have come up with alot of really cool, out of the box ideas, and I hope you reach your goal with all the work you have put into this. I just have one question, and I don't mean any disrespect, I'm just curios and want to know your thoughts and reasoning. What advantages will you gain from a rig at 1200grams? Will it have superior crawling capability over the average rigs out there now ranging between 3.5-4.5 pounds?

[Harvo]

Why did we go to the moon? We didn't have to. We wanted to prove that we could

[obebaldone1]

Good point Harvo. Cant wait to see what you come up with on this one.

[ClassiCutCustoms]

Guys...... I just want to remind you he has another comp rig and he is just wanting a challenge. I have been there and can relate. Sometimes the joy is in the challenge of the journey. I have emailed Tobias extensively and I know he is very smart, respective of others and on the cutting edge of things. He probably is snowed in for the winter months of Sweden and needs something to keep the juices of design going..... Looking forward to what he comes up this time around. The drawings he has shared look amazing......

[Dravpnir]

Thanks for all the kind words everyone. I am really excited to finally have started building a crawler again. I still have some unclearities on a few details for the front drive shafts but in all in all, I have most of the axle design already clear in my head.

Originally Posted by Tgreer

I just have one question, and I don't mean any disrespect, I'm just curios and want to know your thoughts and reasoning. What advantages will you gain from a rig at 1200grams? Will it have superior crawling capability over the average rigs out there now ranging between 3.5-4.5 pounds?

No problem at all, everyone should feel free to ask questions. I feel like Harvo and ClassiCutCustoms answered it nicely

Originally Posted by Harvo

Why did we go to the moon? We didn't have to. We wanted to prove that we could

Originally Posted by ClassiCutCustoms

I just want to remind you he has another comp rig and he is just wanting a challenge. I have been there and can relate. Sometimes the joy is in the challenge of the journey.

One has to have a goal with a project and weight is quite easily measureable. Loosing weight on a rig also requires that you push the limits and for me those limits are to learn working with new materials. I really look forward to start lathe the titanium rods I have laying at my desk.

Regarding if a lighter rig will have better capabilities than a heavier, I am not really the person to answer to that. I probably have atleast 30 times more build hours than drive hours with crawlers...

[Dravpnir]

I didn't work with the lathe today, instead I test mounted the gear boxes. Everything fits and the gear mesh is unpleasantly.... smooth!
Really big thanks Barry, for sharing your gear distances!

I also took my time to sand the edges of the carbon fibre and seal it with CA-glue. That is why the edges are so shiny.

The spacers, drive shafts and upper link mounts are only there so I could check the fitting of the gears, ball bearings, screws and so on. Now that I know everything is good to go, I will start to mill the middle delrin parts and start to lathe the titanium drive shafts.

Also I will not use the motors in the pictures, they are just there for the same reason as the spacers. Even though I probably will not use big 540 motors, but I would like to have the option to use that size of motors if I want.

I designed the gear boxes so I can use from a 11T pinion to a 17T pinion.

Front gear box








Rear gear box








Both together

[Tgreer]

What gears you running there? Your lightest options will be some milled down plastic large gears from an Mad tourqe crawler. Then use rcbros locker and fourth gear.

[Dravpnir]

Originally Posted by Tgreer

What gears you running there? Your lightest options will be some milled down plastic large gears from an Mad tourqe crawler. Then use rcbros locker and fourth gear.

Hmm... you do not know which gears I use and then say which ones which is the lightest... sorry I just had to say that, I am only just messing with you

Thanks for pointing that out. I actually have all those products you mention and the gears I am running is mentioned in the first post.

Originally Posted by Dravpnir

The gears will be the new lightened Berg V3 gears, EBG220.

I like the Berg V2/3 gears actually and I think it is much easier to design gear boxes for them compared to the Berg V1 gears. That and I like my gears to be metal made the choice quite easy for me. Also regarding the price, not much beats the $23 shipped that the V2/3 gears cost.

There is till quite a lot of meat on the V2/3 gears and I will lighten them further in the lathe when I get the time.

Berg V2/V3 Lightened gears (EBG220)



MT plastic gears, MT small gears, RC Bros 4th gear and RC Bros locker



RC Bros large gears, original Berg V1 small gears and RC Bros locker

[Tgreer]

Sorry, guess I over looked that in the first post! Yup, I've always had that combo in my head as being the lightest combo available! Look forward to seeing how close you get to that weight with your V3 gears!

[Tomy]

Looking good, Tobias!

Very nice work on the Ti and aluminum parts. I also like the fact your front and rear gb's are designed differently to best meet different needs front and rear.

I now remember I forgot to send you the 15mm alloy spacers. Will do so asap.

Tomi

[ZZR 1100 Racer]

Nice build, nice parts and also nice looking pics
Interesting to see if you could really finish with 1200. I think it will be not easy to catch.

[RcBro]

Good to see you can gain .5 grams and have beef in your transmission! Build is lookin sick!

[Dravpnir]

Thanks for the nice comments guys!

It won't be easy reaching 1200 g thats true, but how fun would it be if it was easy

It is quite incredible how light your gears are William. Pretty sick that they are almost at the same weight as the plastic gears. If you ever decide to make large gears that fit the small Berg V2/3 gears you will have atleast one customer here

Time for some more pictures. I got a couple hours at the lathe tonight and made some pieces for the rear axle tube.

A pair of new mounting flanges of aluminum. The pieces will be put in the mill to to remove some unnecessary material.



A pair of delrin bushings for the wheel side of the axle tube. I will try to skip the bearing and use a exchangeable bushing instead. If it don't work it is easy replace it with a bearing holder instead. Most of the larger ring around the bushing will be removed. I only save a small part of it to put a screw though to clamp the bushing to the axle tube.



The titanium tubes are cut to right length and the pieces are just put together



Not crazy light, but given the nice ground clearance these tubes gives I am happy with the weight.



Test mounted on the gear box



I will remove some of the material on the aluminum part. I am thinking in line of the black lines.

[BliB]

Dude, think it's so awesome that a guy like you without any real knowledge to work with lathes and mills.
Buys a mill and start to learn cad/cam and start making your own gearboxes and stuff!

Been following your build since the RS10 (in the swedish forum) seeing all the great parts you've made!

You just keep surpricing with the flawless quality!
And everytime we meet you have the trunk full of stuff to show

Maybe we need to meet for pizza and beer sometime during the winter?

[Calderwood]

I have been working on the same idea as you have here, using plastic bushings at the tube ends. I'm not using delrin but it seems to be working flawlessly. The loads are very low at the ends of the axle compared to the loads the gears place on the shafts. Bravo sir!