Hi there again!
Probably some of you got interested in OBTS Chassis when you saw it can also work as an On-Road Chassis with the Tesla Model S Body.
Please, take a look to this chassis with the Tesla Body in action in this video
Tesla Model S is 296 mm wheelbase, while standard Drifting / On-Road cars use to be 255 mm. If you use the parts in this publication you will build a 295 mm wheelbase On-Road OBTS Chassis.
This publication includes a 3d printable Straight Variable Length Center Transmission and also a 3d printable Locked Center Differential. The same way you can use 3d printable MyRCCar Shocks, Motor Pinions and 12mm HEX for the wheels to save quite a good amount of money :)
Most of the parts in this publication are just a selection of the ones available in the OBTS Chassis publication.
The 295 wheelbase is achieved using a 145 mm Front Partial Wheelbase and a 150 mm Rear Partial Wheelbase. The 150 mm one is a little longer than 200mm... This can be quite a little problem for you... maybe it is not.
I built this chassis with a 6º Caster in the front axle and 0º in the rear one.
The Center Differential Housing is in the "centered position" this time, so all the central transmission is aligned and the space for the battery is reduced.
I use a new "Low-Profile" Butterfly in the front because of the shape of the body. This allows using 60-70mm from hole to hole shocks.
I'm using Mission-D CVDs in my build, but I also designed it and share the parts for HSP 102015 and 122015 CVDs. Mission-D CVDs are extra short and I'm using special 3d printed wheel HEX to put the wheels as far from center as I can.
The holding system for the body is quite simple and can be 3d printed mostly in PLA but I think this time the body won't resist much hits. I didn't hit nothing seriously with my Tesla Build, but I feel the day I hit something the body will break quite sure!
This time I'm not going to enter in so much details but anyway I'll try to provide some info about the different parts of the build. Lets go!
You will have to print and assemble the main chassis as a start point. You will have to print the next parts:
To assemble this parts correctly you can take a look to the original OBTS Chassis Publication. Your battery can be as long as 160mm but only 42 mm wide to use the standard battery holding system. I plan to design a box to solve the problem for bigger batteries, which would be inserted in vertical, the second larger measure of the battery aligned with Z axis we could say...
This parts are also common for any OBTS build. The simple center diff housing must be mounted in the centered position. You will build a 6º Caster front axle and 0º Caster Rear axle.
1x MRCC_OBTS_CD_ADAPTOR *
If you want to use little longer shocks in the rear axle there is space enough so you can use the Normal Butterfly if you want there. The same than with previous step, you can use the original OBTS Chassis Publication as a guide to assemble this parts.
I reduced options in this publication to make it easier to understand. So The supplied steering parts are for 5x10x4 bearings.
2x MRCC_OBTS_ST_BalljointExtreme_Medium or Small
To build the steering links and servo link you can use Normal, medium and small Ball-joint Extremes with M3 screws of proper length with the head cutted. Remember you will need 6x 4.7mm Balljoints with M3 screw to use this links.
Most of this parts will depend on the CVDs you want to use, so print the ones for your CVDs.
I plenty tested the Mission-D CVDs and the wheels (61mm diameter) can perfect steering under the Tesla Body.
I also tested The 475 Lower and Upper arms with some adapters for my CVDs. The position of the wheels with this arms is about 10 mm outer, so it can hit a little with the Tesla Body when full turning. Maybe you have to "sand" a little some parts of the front mud-guards of the body to have the best steering.
4x MRCC_OBTS_SUS_LA375_ONROAD (For Mission-D CVDS) or
4x MRCC_OBTS_SUS_LA475_ONROAD (For HSP 102015 or 122015)
2x MRCC_OBTS_SUS_FSBLOCK_TYPEA_ONROAD (For Mission-D CVDS) or
2x MRCC_OBTS_SUS_FSBLOCK_TYPEB_ONROAD (For HSP 122015) or
2x MRCC_OBTS_SUS_FSBLOCK_TYPEC_ONROAD (For HSP 102015)
2x MRCC_OBTS_SUS_RFBLOCK_TYPEA_ONROAD (For Mission-D CVDS) or
2x MRCC_OBTS_SUS_RFBLOCK_TYPEB_ONROAD (For HSP 122015) or
2x MRCC_OBTS_SUS_RFBLOCK_TYPEC_ONROAD (For HSP 102015)
You will need one UPLINK KIT for each wheel. Use the proper M3 screws head-cutted to assemble the four upper arms needed. To assemble the rest of the parts in this step use the previous OBTS Chassis Publication.
The Body Mounting System
This time the Body Mounting System consists in 2 sides for the chassis (with two holes each) and 2 side parts for the inner of the Tesla Body which can be mounted with the same screws you need to hold together the Tesla front and centrer big parts with the lower sides.
This side parts for the inner of the body has 2 cilinders each which will enter into the chassis sides holes. You will have to stretch your Tesla Body a little to put it in the chassis.
The cilinders in the side parts need to be completed with a TPU ring and a PLA cap. This way the cilinders will enter in the chassis side holes until the ring fits its place at the end of the side holes.
I published the left side parts so remember to print the symmetrical for the right side.
1x MRCC_TMS_Holder_BodyLeft + symmetrical
1x MRCC_TMS_Holder_ChassisLeft + symmetrical
This holding system is not ideal but a quick solution I found. Feel free to design other holding systems and please share with us!
The extra saving (money, not time) parts
THE CENTER TRANSMISSION
Hey! This is the only real NEW THING! Is the reason why the center diff. housing must be mounted in the centered position...
After designing the universal shaft for the MTC Rigid Axles I thought I could use same "adjustable length" concept for this straight transmission.
You will need one inner axle part (the 10mm one) and one outer axle part (the 12mm one) to build an axle which would replace a dogbone. You will be able to fit the 10mm part head into the 1/10 standard vase of F/R diffs and the 12mm part head in the 1/8 center diff vases or the 3d printed center diff. locked version. Use a M3x16mm counter-sunk screw for the center diff heads and M4x5 grub screws for the 1/10 vase heads.
THE CENTER DIFFERENTIAL
The same than in MTC Rigid Axles Version, a locked 3d printed differential can be used here. As the transmission is straight, the requirements are more forgiving.
You can build it using two 12x18x4 bearings, the same you would need to use the SST center diff. or with two 10x15x4 bearing, easier to source ones. They will only work with the 3d printed center transmissions, not with sourced dogbones. Maybe in the future I design a version to built with 1/10 universal cups /vases so it could be also used in other builds.
Using 10x15x4 bearings:
Using SST bearings and Holders:
Choosing a motor pinion is the way you will be able to control your max speed. You can also change Motor (different KVs) or use other center diff with 44T as the trooper, but for an initial calculation lets suppose:
- 61mm diammeter wheels
- 4000KV motor in 2S = 29600 max RPM
- 14T/46T and 13T/38T Total Reduction = 9,6
This parameters would give us a max speed of 35Km/h
From there is easy to know what max. speed with a 3000KV motor or with 18T pinion. Multiply 35Km/h for 3/4 for the first one or multiply it for 18/14 for the second one :)
I publish here the 14T pinions for both 3.17mm and 5mm diameter motor shafts. To get the perfect one for you maybe you can try My Motor Pinion Customizer.
THE WHEEL HEX:
I publish here some HEX I previously designed and which are being really useful for me.
If you are using the Mission-D CVDs you will need what I call a 5Plus1, an HEX 5mm tall with an extra 1mm lip. If you have some problems because your wheel hits some part while steering maybe you can use taller HEX if your CVDs allow it.
I imagine the same will happen using HSP CVDs. If you try to use 4mm tall HEX or maybe also the 5Plus1 your wheel could hit some other parts. I hope you can use taller HEX with those CVDs and the wheels turn correctly. As an start point I would try:
If you are using Mission-D CVDs and want to have your wheels as far from the center as possible, you can use 9plus1mm HEX.
If you can't find the four shocks you need at the price you desire but can get four springs and maybe some O-rings then you could think about building your MyRCCar Shocks! Is a lot of work but they perform near a sourced one if used with sourced springs.
I'm using them in the front axle in my build. I had some longer than needed springs but I gave them a try anyway. As they are a little compressed in the most extended position of the shock, this increases the pre-charge, so my regulation rings are at the top and they are a little harder than I would like.
The provided body in this publication is to assemble 70mm from hole to hole shocks. I think with the proper 40-45mm springs (big bore ones) they allow a good travel for the suspension.
To build this shocks you will need to print TPU, cut 3mm piano wire, some shock oil to put inside the shocks... some Loctite to glue the axle with the piston and the foot... You can find more info in the original MyRCCar Shocks Publication. To build four shocks you will need to print:
4x MRCC_SHOCKS_LinkSpacerHead_TPU or longer version
4x MRCC_SHOCKS_LinkSpacerBottom_TPU or longer version
4x MRCC_SHOCKS_SealBottom_TPU (better if sourced)
I designed a 3d printable compatible spring and tested it for a while for the 100mm MyRCCar Shocks. I'll try to do a 45mm version and test with this shocks soon!
Of course you can use sourced shocks in this build too! I think anything between 60-70mm from hole to hole will do the work.