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View Full Version : trying to build a race worth revell rpmz


acerpower
2008.11.21, 05:50 PM
I bought a few revell rpmz from walmart on clearance a while back and they have been collecting dust in the closet ever since. i recently purchased a miniZ
mr-02, and that re-kindled my interest in the rpmz. the chassis is somewhat similar the miniZ the major difference is the rpmz use aa cells. i plan on installing some aaa cell holders to keep the weight down.
i've already found out that miniZ wheels fit on the rpmz and also the diff from the z will fit with a little shimming, which is great because the rpmz diff is awful.
with the adjustable wheel base, and the use of Z wheels and it's various off-sets, it shouldn't be too hard to fit a selection of bodies on the rpmz.
which is good because the included nascar body is a tank, and doesn't look close enough in scale to the z.
i don't plan on spending much on this build, i'll be mostly using spare z parts.
i may have to fabricate some H plates but, i have some cf of various thickness's
hanging around so, that may be an option.
so far i'm just toying with the idea so, i might bail on this project if i'm not happy with initial results.the rpmz can be purchased at walmart on clearence for around $25, and the pcb and tx are vastly superior to the xmud so it may have potential. any ideas or feedback is welcome and appreciated.

Red Team
2008.11.22, 01:05 PM
Would be nice to see some pics of this chassis !

acerpower
2008.11.22, 04:50 PM
ask and you shall receive...........
here we have the stock revell rpmz made by auldey. similar in design to the miniZ but larger and much cheaper. i got this one on clearance for $25.
http://pic1.picturetrail.com/VOL1138/4322912/9104237/344245119.jpg
the stock wheelbase is 115mm and the wheelbase of a mr-02 rm is 94mm.
here is the size difference...................
http://pic1.picturetrail.com/VOL1138/4322912/9104237/344245125.jpg
you will notice that the miniZ uses aaa cells and the rpmz uses aa.
this is some thing i will change.i believe that the weight of the aa cells will greatly hinder acceleration and handling so, i'll be cutting the chassis to install aaa cell holders and maybe shedding a little weight.
i'm still not completely sure what i'm doing with this thing. if i can't find a body that fits to my liking
i might bail on the project.
my goal is to spend as little as possible and try to keep the whole build under $50 (including car)
and hopefully be able to keep up with miniZ.
i just met a local miniZ club and hopefully i'll be doing my testing on a rcp track whith a real lap timing. only time will tell.............................. ;)

acerpower
2008.11.22, 09:39 PM
i started by removing the motor pod and installing a stock miniZ diff. the z diff isn't great but it's a little smoother than the stock diff plus it brings the track width down to the z's size i also put on some 0 offset z wheels for mock up i'll change them when i settle on a body.
http://pic1.picturetrail.com/VOL1138/4322912/9104237/344251287.jpg
as you can see it looks strikingly similar to a miniZ rm pod. i don't have any ball bearing yet but the z ones will fit and i'll order some. i had to shim the diff a little on both sides to center it.i used some old bushings for that for now.
next i cut the chassis to remove the aa cell holders and install the aaa holders.
http://pic1.picturetrail.com/VOL1138/4322912/9104237/344249893.jpg
notice the z wheels on the front. the front axles are a little long but i made some spacers with some old bushings to make it work.
i still need a motor and bearings maybe more but i want to keep the cost low. i'll save my money to mod my Z.
i'll post more pics in the future to show some further progress but thats it for today.
i'll try to do more tomorrow.

FastTRX
2008.11.22, 11:52 PM
Interesting pictures. It very much resembles a RM MR-015...except waay longer! That wheel base definitley needs shortened! And how about the length of that rear shock??! With the addition of a kyosho rear end, rear suspension system, and CF T plate and tires and wheels you might have a performer for a verry cheap price! Thats assuming the electronics are good enough to handle a hotter motor and have slightly better reception than the horrible Xmods. But for $25 I would have to wonder.

I wonder how the geometry of the chassis will work with the changes. There seems to be a high C.G. just from the looks of the main chassis where the battery trays would normally be held. You'll definitley have to let us know how it comes along.

acerpower
2008.11.23, 09:43 AM
the reception is way better than the xmod, more along the reception of a miniZ
(27mgzAM) in fact i sometimes use the rpmz tx to control my Z.
i'm not sure how hot of a motor she will run, i'll probably do my testing with a
pn 70t stock in the rpmz and the Z to see how they compare.
i do see a hotter motor in the future and maybe an fet stack in the more distant future.
the c.o.g. seems to be my biggest problem although, without those monster
wheels and tires the car is much lower.i'll know more after testing.

acerpower
2008.11.23, 04:33 PM
after the chassis was cut the aaa trays were fastened in place
http://pic1.picturetrail.com/VOL1138/4322912/9104237/344352605.jpg
i also replaced the motor pod. the chassis has several mounting positions for different wheelbases. the wheelbase in the picture is now 100mm.
here you can see a size comparison:
http://pic1.picturetrail.com/VOL1138/4322912/9104237/344355018.jpg
as you can see, the rpmz is close to z size with no modification to the chassis other than the battery trays.
now the stock rpmz chassis with batteries and no body weighs 235.7 grams
and the modified rpmz: with batteries and no body weighs 155.4 grams
of course, the weight of the modified rpmz will be a little higher after a new shock or disk damper is added but i'd say there is some substantial weight loss
with the simple mods i've made.my mr-02 weighs 99.7 grams with out body or batteries and the modified rpmz weighs 108.2 grams.i could remove a little more plastic from the chassis to get it a little lighter but, i'll wait on that.
now i have to order a few parts. i need a cheap, lightweight, and durable Z style body that can fit the 100mm wheelbase. any ideas?

Red Team
2008.11.24, 08:30 AM
Nice...for the body I would try to fit a PN Pancar body, adjusted a bit with a dremel.

XMDrifter
2008.11.28, 03:01 PM
well, the rpmz IS supposed to be a 1/24th scale rc.
i agree with the rpmz having much better electronics.
if i wasn't broke now, i'd swap an RPMz system into my xmod asap
but you'll have to be careful because the servo assembly on the rpmz is weak and easy to break like the mr01's
just a caution

acerpower
2008.12.04, 12:51 PM
i'm hoping this thing will much faster on the track than any xmud with upgraded pcb. i have a few xmods with hobby ep's and they leave a lot to be desired in handling on any track.
i am considering a mosfet uprgrade. i have some 4562 fets but, i'm not sure if they would work on this board. the stock fet have the number 8938.
i know nothing of these mosfet's and there limitations.i might push them and find out.
anyway, i suppose just about any board of this type should benefit from a fet upgrade.
i might also use a stock koyosho rm motor pod. i have an extra one and the motor is lower on the stock z pod thus lowering c.o.g.
a stock z rm pod is about $6 and might be a worthwhile upgrade plus, you can use the 2 bearings from the stock rpmz pod.
for the body i'm considering an unpainted miniZ ford gt.
looks like might fit.

acerpower
2008.12.11, 12:56 AM
now since i'm probably going to use a miniZ or iwaver body, and i'm definitely using the z wheels i had to do something about the front axles being too long.
as you can see in my previous pics, i had to put a bushing as a spacer between the wheel and the nut.this looked goofy, plus without a servo saver, it could get hung up and strip the servo gears.
i came up with this solution:
http://pic1.picturetrail.com/VOL1138/4322912/9104237/346718667.jpg
i pulled the axle pin from the knuckle, added a spacer i made from a bushing i sanded down to the correct spacing. i then re-inserted the axle into the knuckle. now the axle doesn't stick out too far with the z rims.
here is a pic with the miniZ rm mount,miniZ diff and pinion, and miniZ stock motor.
http://pic1.picturetrail.com/VOL1138/4322912/9104237/346659059.jpg
the stock rpmZ t-plate works with some very slight modification but, i plan on using carbon fiber t-plates made for a Z with a small modification to the chassis. this is easy and i'll show how it's done in my next installment.
so far the drive train from the z is allot smoother than the stock rpmZ set up, a 3racing outer tune ball diff would be a cheap upgrade and give some more tuning options, so that might be in the future. the use of z wheels and t-plates will make the rpmZ much more tunable to different track surfaces. i'll try her on an rpm track as soon as i get the body.
now i need to figure out what to do for damper plate system.