Prepping a 870C runner - questions and progress.

[BloodClod]

This thread was previously "YZ-870C mounting top deck?" but I renamed it so I didn't have to create a new thread.

Hi guys,

Wondering if anyone can help me on this one. I'm in the process of restoring a 870C and I wanted to fashion a top deck for it - what I'm trying to figure out for the later cars that did have top decks is how they are attached to the bulkhead covers.

Anyone have some pics and can describe exactly where and how they mount?

Any info would be much appreciated.

BTW, what length shocks (hole to hole) does this car use front and rear?

Many thanks in advance.

[jwscab]

all top decks are aftermarket for the 870c, since it used a spine plate just for reference.

most bolted in place on the front and rear bulkhead with 4 longer 2mm screws, either with or without a special spacer underneath. Approx 20mm long, I think. The brace also picked up one or both sets of the center shaft screws, also 2mm, and also longer because of the extra height.

a jammin' upper brace also extended forward and made light contact with the front tower, to better support the relatively weak mounting system.

standard retrofit associated shock sizes (per associated and yokomo) are .56" in the front, 1.02" in the rear.

[GJW]

[Mr. ED]

Or you could could get the works 91 upto 93 gearbox covers which have provisons to mount a top plate already

[BloodClod]

Awesome guys! Thanks a million for the quick answers - totally on the spot!

I'm prepping this car for a vintage event locally - any particular part I need to be careful with or to reinforce?

Heard the magnesium front bulkhead is particularly weak?

[xxxmain]

I'm prepping this car for a vintage event locally - any particular part I need to be careful with or to reinforce?

Heard the magnesium front bulkhead is particularly weak?

When you make your top deck be sure to copy the Jammin design and extend the front so that it kisses the back of the front shock tower as jwscab mentioned. This will support the front tower in a crash and prevent the flex backwards that would normally break the brittle magnesium front bulkhead. I haven't run a Yokomo in a while (restoring a few right now) but I know that once I installed my Jammin upper deck many many years ago, I never broke a front bulkhead again.

[BloodClod]

Thanks for the good advice I will definitely do that!

So the part on the bulkhead that typically breaks is the shock tower mounting point eh?

Any other guys run their 870C regularly and have tips to improve the durability of the car?

I bought the car used and after taking it apart for a good cleaning it was left in pieces for months... finally got to putting it together last night in preparation of our vintage run.

Here are some progress pics.





Okay one more question - I understand there are differences between the wheels on the 870C and the YZ10. Are the arms and driveshafts on a YZ10 longer to account for the greater-offset wheels?

[jwscab]

I can't give you the exact details of the 870c/YZ10 vs the later YZ10 with regards to arm spacing and rim offsets.

EXCEPT-- those JC wheels you have there need about 3mm extra spacing outward per side in the rear. So they are most likely for the later yz10 chassis, say, 91/93?

I was messing around with one of the ones I have the other night and rebuilt the diff. I noted a few things, maybe it's common knowledge, but maybe not.

the diff balls are 1/8", the thrust balls are 1/16", the diff rings are the same size as the original 6 gear associated transmission, and the thrust washers can be replaced with these:

http://www3.towerhobbies.com/cgi-bin/wti0001p?&W=001336483&I=HPIC0166&P=K

or

http://www3.towerhobbies.com/cgi-bin/wti0001p?&W=001336483&I=LXNTT6&P=K

I have an idea that you might be able to replace the diff pulleys with ones from an xray t2 car, but I still have to verify that. though they are 34 tooth instead of 35.

[BloodClod]

Thanks for the advice and help guys... here's some progress.

I've completed machining the top deck with front shock-tower support. Also made 3mm spacers for the rear wheel adaptors to bring the width out to correct specs.



More info and pics of the car on my blog for anyone interested.

[BloodClod]

Slow and steady on my 870C...





Getting there...

More pics and info...

Quite a bit of slop in the suspension - thought of fashioning a rear brace to hold the hingepins securely and remove some of the slop the pins have in the rear bulkhead. Anyone have tips of removing more of the slop?

Let me know what you thnk.

[Mr. ED]

longer hingepins, 2 balls, 2 cups and a turnbuckle is someting you'll see often. A tailor made brace in carbon should pose no problem for you either. Nice work again on those new parts! Why did you mount that large part under the servo, adding stiffnes?

[BloodClod]

longer hingepins, 2 balls, 2 cups and a turnbuckle is someting you'll see often. A tailor made brace in carbon should pose no problem for you either. Nice work again on those new parts! Why did you mount that large part under the servo, adding stiffnes?

So the solution is to extend all 4 hingepins, add balls on the extra length and then put the turnbuckles on?

The additional part is actually a servo mount as I didn't want to drill new holes in the chassis.

[jwscab]

the only other thing you can do to reduce slop is to ream out the hing pin holes and press in brass tubing, then ream to the desired clearance(if needed). I have done this in some nylon parts, and the hinge pins were 1/8". I used 5/32" tubing. I think the yok stuff is all 3mm though....so you would need to find appropriate tubing.

[a01butal]

I have some RCPS Yok YZ10 Titanium hinge pins for sale that I previous posted in BST. They come with the 1/8" drill bit so all you need is the AE 1/8" e-clips to finish. Pm if interested as I still have several sets.

[slow_jun]

Nice to see you here BC, is this what your going to Run in the Noob Race this Dec?

Yeah, guys here are very nice, ask and you shall be answered, they dont get mad if you ask the stupidest questions....hahaha...

Nice Yoke, one of my fave back in the day. still hoping to get one... working out if i can trade my Shelfer 10 for a Yoke...
Goodluck this coming Dec. a great event i bet.,...