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smiffffy

Blackfoot drive upgrade question

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Hi guys, I have a MB that i have successfully used a frog re release dogbone set to upgrade the drive shaft and move away from the hex drives.

So i thought i would do the same on a BF i recently purchased, the problem i am having though is that it seems the drives are at too steep an angle when at rest compared to the MB.

It looks to me that the 80mm black shocks on the original BF are pushing the suspension arms too low for the dogbone shafts and the dogbones when being driven keep popping out and twisting the rubber drive shaft boot, sometimes locking one wheel up altogether.

The MB with its 70mm yellow shocks seem to be at a more straight / level angle, and by comparison from the rear looks like a low rider.

i have bought some MB 70mm shocks off the bay to see if this resolves my problem when they arrive (yep i know i could try them off of my own MB but heh we all need spares to fill the tool box).

My question is, should i have bought a longer dogbone drive set and if so does anyone know of a set that would fit that are slightly longer.

is this a known issue when trying to upgrade the drive shaft of a BF.

I assume all i will be doing by reducing the shock length is giving the BF a slightly lower ride.

All thoughts greatly received.

Many Thanks in advance

SMIFFFFY

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hi smiffffy,,

agreed , a picture would be most helpful here ,

the issue of longer shafts is that they may bind as the suspension compresses , although most tamiya drive shaft cups look the same they often have subtle changes to make up for such issues as you are having ,

post a few pics showing the shaft and cups with boots pulled back, uncompressed , half compressed then fully compressed and i am sure that a solution could be spotted . ;)

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Hi

I think I can visualise what you are saying Smiffffy.

I have upgraded my Original Blackfoot with the ReRe Frog dogbone axels, and I must say, I have had no problems with it (no dogbones popping out etc..). So not exactly sure as to why you are experiencing this.

What (I believe) you are saying, is that the longer 80mm Black shocks are allowing the rear trailing arm to travel further down, and thus, further away from, the gearbox - which in turn is creating a large enough gap for the dogbone to be able to 'pop out' of its sandwiching axels.

(In theory, it should'nt matter which shock is used, as the trailing arms maximum travel should still be the same, but perhaps because the yellow shocks are oil filled, and not so strongly sprung, the weight of the car, especially when carrying a battery, makes the ride height lower, hence why you say the rear end ride height looks lower, and the angle of the dogbones less steep).

Like I say, I have not had trouble with this myself, but I am sure I have read elsewhere some time ago (on the TC forums) of people complaining of losing their dogbones as they have popped out mid run. (Can anyone else confirm this?).

I believe one suggested fix was to use shims to reduce the gap between the sandwiching axels.

I have not had to try this, but, if this is whats happening, would using a washer on the inside of the main axel (where the inside ball bearing is located, inside the black rear trailing arm) work?. This would have the effect of slightly reducing the gap between the sandwiching axels, and hopefully, just enough to stop the dogbone being able to pop out?.

(There may be better ways of doing this also)

Anyway, hope this helps

Kind regards

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hi guys having terrible trouble getting files into this thread, have made them as small as possible but still wont attach ok they have gone in now.

right the MB is the chassis with the drive shafts almost in a straight line and the BF is the one with the shafts almost at 45 degrees. Both cars are at rest with no batteries in them.

The MB yellow shocks are at full extension and actually stop the swinging arm from hitting the red stopper on the underside of the chassis by about 5 mm. The yellow MB shocks measure 70mm centre to centre when on the car and also when off, this is the same for the front shocks and also the back shocks, so i thought hey presto buy a set of MB yellow shocks and problem solved. But nope the yellow shocks have arrived off the bay and they measure exactly the same as the BF black shocks 80mm.

The BF black shocks actually allow the swinging arm to go full distance by stopping at the red stopper on the chassis. these shocks as previously mentioned measure 80mm from centre to centre.

exactly the same chassis but the MB drives sit almost straight when at rest but the BF are at 45 degrees and i assume the reason why the right rear pops out every now and again.

The re-re frog dogbones i have used have the fixed dogbone shape at each end of the shaft and the cup obviously at the gear box and swing arm ends.

i will try the washer at each end as suggested in some forums. I have also looked at other threads that suggest the frog requires 5 rubber grommets in the cups of the drive shafts, 3 on one side and 2 on the other, but it looks to me like this would only push the do bone further out of its cup and make it more prone to popping out.

the washer on the other hand may restrict the axle pin from being pushed through and thus not being able to keep the wheel on.

I am looking also at why i have 70mm centre to centre on my MB shocks and the ones off the bay are 80 mm, I am wondering if the piston rod in the shock is threaded within the shock allowing it to be restricted to 70mm overall length uncompressed instead of the 80mm of the ones i have bought.

i am also wondering if the dogbones could be purchased slightly longer which would make them sit inside the cup a little further at rest and not long enough to restrict the compression of the shock when the swinging arm rises.

very confused ???? and not sure why one sits lower, i can only assume it is the 10mm extra length of the shock on the BF and MB ones off the bay.

Again any ideas greatly received.

Smiffffy

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Hi Smiffffy

Looking at the pictures you attached, what I can say is that the near 45 degree angle of the axel is what you should have (on both a Monster beetle using yellow shocks, or a Blackfoot using black shocks, whether they are using the dogbone hop ups, or the original hex type axels). This is how it should be.

I can only assume that the reason the rear axels are running almost straight on your MB with the yellow 70mm centre shocks, is due to the odd shortness of these shocks you have (unfortunately I don't have mine to hand to measure at the moment, but i'm certain that the yellow & black shocks should measure the same length, probably @ 80mm, I will measure mine and come back to you on this).

Like I say, I have a Blackfoot using the black shocks, and my axels are just like your picture (their near 45 degree) and I also am using the dogbone hop us (bought of ebay, in the blue transmission bag).

I have run this Blackfoot quite a few times, and I have not had any trouble with the dogbones popping out, I have not had to use any shimes or rubber grommets).

Regarding the grommets...

(I think you should've got some of these included in the blue transmission bag right?)

Try popping one, in each cup, of the drive axels (which come out of the gearbox).

And also, pop one, in each cup, of the long axels (which connect to the rear wheels).

This will hopefully reduce the amount of 'play' in which the dogbone has to rattle about in, from BOTH sides. If one grommet is not enough, try adding another.

Kind regards

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hi again smiffffy,

i see what you mean, that is a rather extreme angle , as gripper suggests ,try the rubber grommets or O rings in the cups there should be just enough packing to stop any slop in the dogbones when the are at the level point or parallel with the ground without binding up the drive system ,

an easy fix in mean time would be to add an internal spacer to the shock shafts to limit down travel , you will lose a few mm of suspension travel but it should stop the d-bones popping out until you get the new drive shafts fitted ;)

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I can confirm that the MB & BF shocks are the same length about 80mm eye to eye & the piston rods are not threaded on either (except at the bottom for the spring cap)

Not sure why yours are shorter, perhaps someone installed shorter piston rods? are the shock bodies the same size as the new one you bought?

As Gripper said the steep angle of the dogbones looks to be correct. I run the dogbone set up in my runner MB running a 15t motor & Ive never had one pop out(I do have one grommet in each drive cup)those uni's should work fine too.

I also have MB & BF shelfers with the original hex drives & the angle is the same.

Blackfoot

SDC10901_zpsf82db3a9.jpg

Monster Beetle sorry rule's a bit hard read

SDC10904_zps7805a421.jpg

MB in the middle is my runner with dogbone set up

SDC10905_zps8b6e1278.jpg

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Sadly the 4mm rubber O -rungs arent part of the transmission bag and it is only after reading the threads on here that i downloaded a frog manual and can see the two o rings at one end and one at the other end on each shaft.

Looking at the manual it seems they are part of the "rod bag" with the drive shaft gator .

oh well back to the shops looking for a 4mm o ring - does anyone have one they can measure, the ebay seller i am looking at does them in packs of 10, the o-rings seem to be measured from inner surfaces across the diameter of the ring and then are measured across the thickness of the rubber itself. i can get a 4mm x 1mm.

hang on just found these there must be one in here to fit

http://www.ebay.co.uk/itm/180pc-Small-Mini-Rubber-Washer-O-Ring-Seal-Set-/271162029641?pt=LH_DefaultDomain_3&hash=item3f22843649

The frog packet just states a 4mm o-ring with no thickness.

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Still getting the dog bones popping out on one side, I have changed the re re frog double ended dog bones for a set that is fixed at one end in the drive cup via Allen key, but is dog bone at the other end off of e-bay. Still the same, I am now awaiting a shorter set of shocks at 70mm the same as my MB ones as I see this as the only way to resolve it .

The frog double ended dog bone seems just a little too short at 40mm from outside edge to outside edge ( 36 mm bar to bar).

Have been trying to find a set that are maybe 42 or at a push 44mm long in total that will fit the frog re re drive cups.

Another suggested solution was to get a wider bearing in the swinging arm, they are currently 5x11x4mm wide but I cannot locate a slightly wider than 4mm bearing so was also going to try a washer at the risk of the axle pin hole then not being visible enough to put the pin in.

Will await the shorter shocks and see what happens I think.

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There are 2 different lower eyes for the yellow CVA's , one is longer than the other (or one is shoter than the other depending on your point of view ;) ).Have you tried inserting a plastic spacer inside the BF dampers to reduce the arm 'drop' at full extension and thus reduce the 'eye to eye' length of the damper in turn stopping the shaft dropping out . This was common problem on early FAV / Wild Ones and tamiya re-modeled the rear arms with oval stops to prevent the arm falling too far with damper at full extent. I used to put spacers inside my old FAV dampers until I got the re-modeled arms

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You should definitely put some limiters inside the shocks. The ORV rear suspension arms have down-stops molded into the underside that hit the bottom of the chassis to limit the travel of the arm, and over time, these wear down or wear a little groove in the bottom of the chassis and that lets the arm drop down too much. This problem is made worse by the shocks being slightly too long and the springs being very stiff. Just add enough spacers inside the shocks to shorten them enough so that the shock, not the down-stop, determines how far the arm drops. On my Blackfoot, the shocks are almost exactly 3 inches (76 mm) eye-center to eye-center.

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Hi ,mark and Kev, yes this is one of my posts but for some reason i didnt get the e-mail alert that it had any more replies after my last one on this subject.

Have got the alerts for my other post though and it has led me here.

Anyway thanks for the info it is greatly received and it has given me a few more things to check out.

When you say that there are two different length lower eyes, do you mean that at manufacture by Tamiya there are two different types and that i may have the longer ones on the model i have whilst others may have a shorter set? or is this something that is done in model build stages i.e when we put it together originally out of the box, you have a choice of set up?

I will hunt down the manual for the beetle and blackfoots and have a good bedtime read or a quick glance of the piccies should i say.

I am assuming that if i am fitting some 70mm ali shocks i have just bought this may solve my problem once and for all without the need to place the spacers in (unless i want it to look as it did for a shelf model) mines a runner for sure so not a problem in fitting the smaller shocks.

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Hi guys, well I have had another bash at sorting the popping out dog bones.

Firstly- putting a washer on the inside of the swinging arm driveshaft still allowed me to put the pin through the driveshaft and fit the rear wheel locator over the pin, but upon fitting the wheels it locked them tight to the outside of the trailing arm, obviously no good.

I am using this type of dog bone set which seems to suffer the same popping out as the one in a frog rerelease transmission gear bag which is a loose double ended dog bone.

http://www.ebay.co.uk/itm/111000655297?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

I still haven't received my 70 mm shocks so took your advice and placed a spacer in the Blackfoot black style shocks ( no shock oil), I did this by using one of the small guide sleeves that goes through the shock fixings eyes, placing this inside the shock on the shaft, this has worked brilliantly and seems to have solved my problem, well done guys and thanks for the heads up.

As an aside I did also notice that ther was slight sideways play on my trailing arms , so I have replaced the plastic P shaped cover that holds the trailing arm in place, one on either side . I have used the metal Ali ones that also come in a frog rerelease transmission bag

http://www.ebay.co.uk/itm/151022368378?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

This seems to have taken all sideways moment out of the equation and seems to help, think I will have to add the third hole in the metal bracket though, as it only has the top two holes and not the three that the plastic bracket has.

Thanks again and I'll see how the drives fair under a beach bashing next week .

Smiffffy

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Good news , I like the look of the metal retainers better than the plastic, they polish up well too

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