Custom Buggy Thoughts

[joeling]

Hi,

Well, on the second of the New Year, I’m having some evil thoughts on 1/8 brushless buggys. I have done a buggy conversion in 2005/2006. Just managed to run it more consistently in the last few weeks. I feel it is time to improve further.

Target :

To make a 1/8 buggy that handles like a nitro buggy with improved layout. Not just trying to fit components into available space on the donor buggy.

Spec. :

1) XL sized motor
2) Low KV high voltage (probably a Feigao)
3) Esc that can handle 8S (probably a BK)
4) Retain center diff
5) Custom chassis, diff holder, motor holder, etc.
6) 8S lipo (3000mah or 4000mah) modeled after Maxamps pack size

So, this so called ‘project’ is still all in my head & may or may not take off. I am thinking of having a custom Aluminium chassis made . This will get rid of the mud guard & raised lip of the donor Al chassis. Some components will be rearranged to target having weight closer to the center line of the buggy. In addition, the front / rear weight distribution of the buggy will be considered as well.

Challenges :

1) Where on earth can I get some custom fabrication done ?
2) Who can supply some custom dog bones ?
3) Money
4) Is having all the weight closer to the centerline better or lower done on the chassis for lower CG better ?
5) How to keep the chassis stiff now that I have removed the lip ? (probably can add lip to the new chassis
6) Is the relocated steering servo up to the task ?

After shuffling all the components around, I have arrived at a layout suspiciously similar to the carbon buggy kit a guy from Germany sells. I hope this is ok as I am only doing this for myself as a DIY one off.

Anyway, have a look at the preliminary pic I have attached. Feel free to comment & recommend someone who can make this happen for me (i.e. I need someone for custom fabrication). The front & rear bits will probably come from a spare Jammin’ buggy I have lying around.

Happy New Year !


Regards,
Joe Ling
Malaysia

[BP-Revo]

If the ESC was rotated to fit parallel to the batteries right above the front dogbone, it would probably give a better CG.

I think RC-M Mike does some custom work. Send him an email.

[jhautz]

I love seeing the totaly custom builds. You should try it. I'm sure Mike could ake you some of the components like the diff and motor mounts you need. I think he can even get you custom dog bones if you need them. Not sure if his mill is big enough for a chassis though.

I like the thought process you are using here. I have few questions/things to think about on your layout.

1) Are you planning to use a really long steering linkage to connect the steering servo all the way at the back of the chassis?

2)Will the front dog bone be strong enough at that length?

3) To add the extra chassis stiffness you want you could use conventional front and rear chassis stiffeners and then make the battery boxes out of a rigid material like Carbon fiber and bolt them down to the chassis tightly so they act as a structural element in the chassis.

4)If you are able to move the center diff that far back, you probably don't need to make a custom chassis that wide. Moving the diff that far back allows you to get the lipos so much closer to the center of the chassis that you will be able to keep everything inside the lip on the chassis anyway. If you can just get the custom dog bones and a custom diff/motor mount you should be able to make that design happen on a stock chassis with some modified mounting holes for the diff/motor mount. Besides the plastic stone guards are lighter than having those whole sections be aluminum anyway adn you can keep the edge lip for stiffness.



EDIT: Got a link to the German Carbon Buggy Kit? Id be interested in seeing that...

[HotnCold]

Nice - good to see another conversion - i have a couple of thoughts to add - i would think about the servo ( as jh mentioned ) - i would shorten the front drive shaft - move the center diff up towards the front more - hang the motor off one side of the diff with a custom diff mount/motor mount - rather than over the top of the diff - you will get better handling with the lower center of gravity for racing purposes, offset the motor weight with batteries and speed controller - and have a shorter throw for the steering servo. As far as support - ( i did this on my HB truggy - ) I placed a custom made brace that runs from one shock tower to the other - rather close to midline in the chassis - threaded on both ends thru the shocktower - worked like a charm - no chassis flex at all - and i used aluminum - so to keep the weight down... And as far as for mikes machine, it should be big enough for a chassis - i know the chassis length will not be a problem. Definately a good start though.......

[GorillaMaxx360]

Very nice but the chassis can be more slimed down for less weight and less metal.

[glassdoctor]

It can certainly be done. I don't know about the custom chassis though... that won't be easy to do or have done.

I have a buggy with the same layout concept but in reverse.... (short driveshaft in the front).

It runs very well.. it was more work than other conversions I have done but it's my favorite. Partly because it wasn't easy to make, and partly because I like the look and it works great.

[joeling]

Gentlemen,

Sorry for being MIA for the last few days. My connection is still pretty slow because of the earthquake in Taiwan.

Anyway, a lot of your ideas are very good. As such, I have revised my drawings & split them into 2 possible versions.

Version 1 is similar to my original drawings with a narrowed chassis. The steering servo has also been relocated to the front. The CG of this option is higher but everything is closer to the centerline of the chassis & the front/rear balance should be pretty good.

Version 2 is showing motor on the front left corner of the chassis but lower to the chassis. The batteries have to be shifted further back. The CG of this version is lower than that of the version 1 at the expense of poorer front / rear weight distribution & components are further away from the centerline. In addition, I have had to extend the chassis by 7mm & the length of the motor is restricted to a max. length of 61mm (Neu 1512 or feigao L cans) only.

What do you think ? Which of the 2 will handle better?

Regards,
Joe Ling

PS : the German guy's thread - http://forums.radiocontrolzone.com/s...d.php?t=196185

[GorillaMaxx360]

Option 1 it looks killer and it seems to have better weight distribution also lower cg is important like in option 2 but it is already low because it is a buggy. In this aspect i think weight distribution is more important because it being a buggy already has a low cg and the one you are building should have an even lower cg than the nitro buggy's

[jhautz]

Nice work!. Both are nice looking layouts with pluses and minuses.

Layout 1 has a higher center of gravity. But I like the way the weight is a little biased toward the front. I think it will help 2 things: Weight toward the front for better bite in the turns and second it will also help keep weight on the front wheels while accelerating out of the turns for better acceleration.

Layout 2 has a lower COG but the weight set farther back spread out a littel wider.

Overall I like layout 1 better. For ther reasons above and it looks a little more original. I havent seen one done quite like that.

[joeling]

Hi GorillaMaxx360 & jhautz,

Thanks for your comments. I am thinking option 1 is more suited for a buggy chassis simply because of space constraint whereas option 2 may work well for a truggy. With the longer chassis, batteries will not need to be placed in such a manner & a longer can motor can be used. Skimming through mags, I noticed that the difference in the wheel base of truggy & buggy is approx 30 to 40mm. Good enough to fit in everything.

Regards,
Joe Ling

[glassdoctor]

Originally Posted by joeling

I am thinking option 1 is more suited for a buggy chassis simply because of space constraint whereas option 2 may work well for a truggy. With the longer chassis, batteries will not need to be placed in such a manner & a longer can motor can be used.

Regards,
Joe Ling

Exactly. I have a buggy and truggy done like this for the reasons you just mentioned...

Have you checked out many conversions that have been done here and at radiocontrolzone?

RotaryRocket and myself have done Kyoshos like #1 and several of us have done truggies like #2 basicly. I can dig up the thread if you haven't seen them.

I think the servo in #1 will have to be above the top plate unless you run some smallish lipos.

[joeling]

Hi glassdoctor,

Appreciate if u could point me in the right direction.

Based on your observation & after relooking at my drawing, I think I need to shift the steering servo back to the rear. The height (thickness) of 4S 4000mAh lipo is around 26mm & the serv could clear that. The horn is interfering with the body shell though.

Regards,
Joe Ling

[glassdoctor]

The servo problem is why I didn't put the batteries up front. I think rcconstructor in germany did his like that in his custom kits, with the servo in the rear. I didn't want to mess with it like that.

That's part of the reason why I did it the other way... put the diff up front and batteries in the rear. It make a really clean layout and it's balanced well.

Remember the battery weight is spread out a lot more than the motor and diff. So actually the weight balance is forward more with the batteries in the rear, I think. ESPECIALLY if you are running a 4s 4000mah pack.

[rotary rocket]

I would personally not do the option where the motor is over the batteries. I did this in my conversion due to space. The problem is the heat of the motor will cook your batteries and vise versa.

Also I would advise to put the batteries in the back and not the front. You WILL need the traction... The disclaimer to this point is glassdoctor's comment about the very light 4s 4000 packs. I use 2 each 2S4P 8000 packs.

The buggy will handle like a charm. The batteries are totally on the chassis (very close to the mid line of the chassis), and the weight of the motor is centered also. You can feel the "torque steer" of the motor though. Yet another reason to put the motor on the chassis like your second option.

If you go with this option I would swap the position of the motor to the other side to minimaize the torque force of the motor. The rotational torque will be towards the center of the chassis, and not towards the outside (left side).

[joeling]

Hi rotary rocket,

Thanks for your comments. I am shifting the weight bias to the rear now. In the mean time, I've done a little more on this. I'm still refining the design & ooking for any potential clashes etc. The next major step will be waiting for my bonus to fund this project :026:

Regards,
Joe Ling

PS : In the mean time, I've managed to kill 2 Quark 125 & a 8XL just when I thought I'm getting the hang of BL. My motor mount decided to get warped & the gear clash between the pinion & spur did major damage b4 I realised. So, no BL for at least a month. Time to concentrate on my driving skills to compete with my buddies:013: