viking252200 5 Posted January 22, 2012 Tamiya Ta05 rally If you want a rally car these days, you don't really have many choices..you can go with Tamiya's Df03 ra or you can try to obtain some of the older stuff, like HPI's RS4 rally, Yokomo's Mr4 rally or Tamiya's Tb01 ... However, despite their undeniable qualities, they all have one thing that counts against them, the lack of spare parts. In my collection, I have a Yokomo mr4 rally, a Academy str4 rally and a Tamiya Tb01..all good cars, but I don't run them as much as I ideally would like to, simply because I'm afraid to deplete my meager collection of spare parts..so I decided to get a modern on-road car and convert into a rally beast! Since I live in Japan, Tamiya is cheap with a good support base, so in light of that, I narrowed my choice down to either a Tb03 or a Ta05v2 A Tb03 would most likely be easier to convert, but I prefer belts, so in the end, I went with the Ta05v2. Without further ado, let's begin.. The first thing, I had to do was to plug all the various cutouts in the chassis, it may be a bit redundant, seeing that it will be protected with an under body, but it looks better I think. I then removed the down stops and filed the chassis to allow for the a-arms to get more down travel. In order to protect the spur gear from pebbles and other debris, I used a small piece of aluminum as guard. The chassis taken care of, I turned my attention to the the diffs... Initially, I went with the supplied balldiffs, but after some thinking I bought a pair of geardiffs, hopefully they should be the sort of set and forget kind of diffs. With the diffs installed, I had to make some kind of diff cover that would protect them from dirt. After much head scratching and many drawings, I made some covers from 0.5 and 1 mm styrene. If the covers do their job, I might re-make the covers in a better material, but for now, they’ll suffice. As you might have noticed, I didn’t enclose the belts completely... since I’m going to run the car with an inner body, I hope that it will negate the need for a belt enclosure...but let’s see. With the diffs covered up, I made a guard for the spur gear, I sort of intend it to deflect pebbles...Though to be honest, I’m not really sure if it’ll do the job... The suspension was actually a quick job... the rear only needed some new ball connectors..Tamiya’s own didn’t allow enough downward travel. The front arms needed to have their braces filed a bit but again a fairly quick job. The only “problem” with the front suspension was the hubs... In order to to be able to dial enough camber in, I had to file quite a lot off, but that in return made the hubs a wee bit weak...I have no doubt that they would have done the job, but I would always be worrying about them breaking. In the end I got some Alu. Hubs from Eagle Racing...built-in 8 degrees of camber and caster. Works perfectly! I managed to get a ride height of 31 mm out of it..not too shabby I think. I used the included shocks, I wanted to use some longer ones, but because the shock towers don’t allow for that, I had to go with the kit’s. I picked up some touring/rally car springs from Tamiya, but even with the softest, they still feel a bit hard..if any of you know of better/ softer springs. Please let me know. For the inner body, I had an old Tb-01 and it was a very close fit, a bit of cutting to allow for the motor, some foam to close some gaps and it was done. Well except for painting. And this is pretty much it...a Tamiya Ta-05 Ra conversion. Whether it actually works, I don’t know yet, I still have to get all the electronics, but I can’t see why it shouldn’t work. Any comments, tips or hints are greatly appreciated. Share this post Link to post Share on other sites
viking252200 5 Posted January 22, 2012 More pictures Share this post Link to post Share on other sites
speedy_w_beans 4272 Posted January 23, 2012 Hi Viking - Nice job on your TA05 rally conversion! I'm almost done with a TT01R Type E rally conversion myself and had similar observations about the stiff springs. Since we're both interested in the same thing, I spent some time today compiling a quick spring rate chart, attempting to find something better. Here's my measurement setup: And here are my results: Basically, TT01R Type E, TB03, TA05, and TA05V2 all come with the same hard silver springs. If you buy Tamiya's 53440 on-road tuned hard spring set, the white and blue springs don't really offer any advantage over the kit silver springs. The yellow and red springs are more interesting, but the red spring rate is still nearly 72% of the kit silver spring rate. All of these springs are really meant for on-road use and are too stiff for off-road use. I started thinking about cutting down front buggy springs, so I captured some measurements from a few of those as well, then predicted a new spring rate based on cutting the buggy spring down to a touring car length. The coil spring effect is really a torsion effect in a smaller package, so as the spring is cut shorter the torsion effect goes up, increasing the spring rate. This is why you see some kids' lowered Honda Civics bouncing out of control; they cut the springs to get the lower ride height, but don't recognize the change in spring rate. The original dampers are not effective at the higher spring rate. Based on predicted spring rates for cut buggy springs, my conclusion is Durga and Sand Viper springs have some merit. Don't bother with the Plasma Edge/Dark Impact springs -- they will end up about the same as the red springs after cutting. The cut Durga spring rate will be about 38% of the kit touring car spring rate, which seems really nice considering how stiff the touring car springs are and how much suspension travel is available on the rally car. I would consider this the "stiff rally" option for the chassis. It may also be worthwhile to cut up a set of Sand Viper front springs and try those too. They should be about 25% of the kit touring car spring rate. This seems like the "soft rally" option for the chassis. You may need to use some preload clips on the damper bodies to regain some ground clearance. I know #400 damper oil works pretty nicely with these two springs in the buggies, so with the 50% higher cut spring rates maybe some #600 oil would work better (use single hole pistons). With kit silver springs, red springs, cut Durga springs, and cut Sand Viper springs you should have a selection of spring rates including 100%, 72%, 38%, and 25%. The lower rates from the cut buggy springs should provide a much more compliant ride, but like the buggies, expect the chassis to bottom out easier unless you install some O-rings on the shock shafts as travel limiters. Also expect to lose some ground clearance -- a softer spring means the same chassis weight compresses the spring more due to lower rates. The measurements in my table are pretty straightforward -- length and diameter meaurements were taken with the calipers, and the mass measurements were taken with the scale. To measure the spring rate I clamped the calipers in a hobby vise, put the scale on top of the vise, and then lowered the caliper until it just barely made contact with the spring. Then I zeroed the caliper, pushed it down 2 mm, and read the new mass on the scale. The spreadsheet converts mass in grams to Newtons and divides by the 2 mm to get Newtons per millimeter. Hope you find this interesting and useful. -Paul Share this post Link to post Share on other sites
speedy_w_beans 4272 Posted January 23, 2012 Here's my rally conversion project... I skipped the DF03Ra rally kits due to past experience with a Dark Impact buggy, and I also skipped the current TT01 rally kits due to ground clearance, plastic drivetrain, and friction dampers. I started with a TT01R Type E chassis, cut the bumper brackets to let the suspension arms droop more, used the longer ball connectors on the shock shafts, and moved the dampers to the outermost holes on both the suspension arms and damper stays. This gave me 21 mm ground clearance with the wheels and rally block tires. There are no issues with the dogbones, diff joints, or axles at full suspension compression and full steering. The benefits of the "R" kit over the a regular kit include adjustable camber, oil dampers, metal shafts/joints/axles, full ball bearings, etc... the good stuff. The undertray is just a few layers of duct tape trimmed with a hobby knife. This should keep the scuffing to a minimum on the chassis, and I can always replace it as needed. Duct tape is cheap! For a top cover I bought some shop rags at an auto parts store and had my wife do a little sewing for me. The idea is the shop rag will keep the bulk of the mud and grit away from the electronics and drive shaft, but it should still allow the electronics to breathe and keep relatively cool. It's not water proof and it's not perfect, but it seemed like a good compromise between shielding and cooling the electronics. The shell is a pre-cut, pre-painted Impreza WRC 2004 shell from Tamiya. I didn't realize this shell was on a TT01 when it was first released; I just bought it because it's winter and it's too cold to paint anything else right now. I need to order some Durga springs, cut them, and give them a try on this chassis -- the kit silver springs are definitely too stiff for off-road use. -Paul Share this post Link to post Share on other sites
DuaneB 2 Posted January 23, 2012 Hi Guys, Don't forget the m-chassis ! I have built a 4WD rally swift by joining a front wheel drive M03 to a rear wheel drive M04 to create a twin motored four wheel drive mini rally monster. The m-chassis gearboxes are easily sealed so its quite a robust little car. You can see a short write up on my car here M03 + M04 = M07 Rally You might also want to look at m-chassis springs for your touring car conversions, the M04 front springs are very soft. Duane B Share this post Link to post Share on other sites
viking252200 5 Posted January 23, 2012 Hi Viking -Nice job on your TA05 rally conversion! I'm almost done with a TT01R Type E rally conversion myself and had similar observations about the stiff springs. Since we're both interested in the same thing, I spent some time today compiling a quick spring rate chart, attempting to find something better. Here's my measurement setup: And here are my results: Basically, TT01R Type E, TB03, TA05, and TA05V2 all come with the same hard silver springs. If you buy Tamiya's 53440 on-road tuned hard spring set, the white and blue springs don't really offer any advantage over the kit silver springs. The yellow and red springs are more interesting, but the red spring rate is still nearly 72% of the kit silver spring rate. All of these springs are really meant for on-road use and are too stiff for off-road use. I started thinking about cutting down front buggy springs, so I captured some measurements from a few of those as well, then predicted a new spring rate based on cutting the buggy spring down to a touring car length. The coil spring effect is really a torsion effect in a smaller package, so as the spring is cut shorter the torsion effect goes up, increasing the spring rate. This is why you see some kids' lowered Honda Civics bouncing out of control; they cut the springs to get the lower ride height, but don't recognize the change in spring rate. The original dampers are not effective at the higher spring rate. Based on predicted spring rates for cut buggy springs, my conclusion is Durga and Sand Viper springs have some merit. Don't bother with the Plasma Edge/Dark Impact springs -- they will end up about the same as the red springs after cutting. The cut Durga spring rate will be about 38% of the kit touring car spring rate, which seems really nice considering how stiff the touring car springs are and how much suspension travel is available on the rally car. I would consider this the "stiff rally" option for the chassis. It may also be worthwhile to cut up a set of Sand Viper front springs and try those too. They should be about 25% of the kit touring car spring rate. This seems like the "soft rally" option for the chassis. You may need to use some preload clips on the damper bodies to regain some ground clearance. I know #400 damper oil works pretty nicely with these two springs in the buggies, so with the 50% higher cut spring rates maybe some #600 oil would work better (use single hole pistons). With kit silver springs, red springs, cut Durga springs, and cut Sand Viper springs you should have a selection of spring rates including 100%, 72%, 38%, and 25%. The lower rates from the cut buggy springs should provide a much more compliant ride, but like the buggies, expect the chassis to bottom out easier unless you install some O-rings on the shock shafts as travel limiters. Also expect to lose some ground clearance -- a softer spring means the same chassis weight compresses the spring more due to lower rates. The measurements in my table are pretty straightforward -- length and diameter meaurements were taken with the calipers, and the mass measurements were taken with the scale. To measure the spring rate I clamped the calipers in a hobby vise, put the scale on top of the vise, and then lowered the caliper until it just barely made contact with the spring. Then I zeroed the caliper, pushed it down 2 mm, and read the new mass on the scale. The spreadsheet converts mass in grams to Newtons and divides by the 2 mm to get Newtons per millimeter. Hope you find this interesting and useful. -Paul Excellent information! Just what I was looking for! I think I need to go to Akihabara and pick up some of the springs you mentioned Another option(so I've heard) is to use springs for Kyosho's mini inferno... If I can find some, I might try them out. Share this post Link to post Share on other sites
Butler 338 Posted January 23, 2012 Cool conversions, nice to see a different approach to rally cars. Share this post Link to post Share on other sites
