Tamiya 501 wishbones on a BJ4 Worlds...

[Hairy Spider]

Hello all,

Maybe this is old news but I've put Tamiya TRF 501X arms on the front of my BJ4 Worlds and I thought I'd share it with the group

First up, some pics of the JConcepts and Tamiya arms side by side for comparison








Now to the nitty gritty of what you need to modify





Finally, a couple of pics of the car with one of each type of arm fitted so you can see the difference








Some notes on the conversion:


1. The distance from pin to pin on the Tamiya arm is fractionally longer than the original JConcepts arm (~1 mm)


2. It would probably be possible to modify the bulkhead and plastic insert to reduce the work required to replace the arms in future. It might actually be possible to make the Tamiya arms a direct fit at that end thus reducing the mod to a simple drilling out of the hinge pin holes at the caster block end. This is obviously the more preferable route but I didn't want to trash a bulkhead if the arms didn't fit for some reason. If/When I break one of the arms I will probably look at the bulkhead mod.


Anyway, hopefully this will have been of interest to some of you as I know there was some speculation in the forum as to weather it could be done.


Regards,
Jon.

Faversham Off-Road Car Club

[trekkerkk]

nice work jon very pro,
most impressed

trekkker

[jimmy]

Good stuff jon, I test fitted the arms when I got the 501X but never had time to put the arms on (and don't have my BJ4 at the moment) but I think these will be a great addition to any BJ4we as they are reet strong.

[OldTimer]

We have done the swap on one S4 to the 501 wishbone, Fred our french driver did the mod after breaking a load of standard wishbones.

[craigosh]

what size diameter did you have to drill the arm out to?
is it just the hub end?

cheers

craig

[JaJoKo]

Wouh, I didn't know that the 501X Wishbones are so much thicker.

Jason, what about producing wishbones like this? Is this much work?

[Hairy Spider]

Hello All,

Well I couldn't let it lie so here we go with a bulkhead mod...

The Holy Grail here was to take a stock unmodified 501 arm and fit it to the car. I'll tell you now that I didn't do it. Physically it can be done (bar the drilling of the outer hinge pin holes) but I chose not to and I'll come to that in a bit. The next best thing obviously is to minimise the time and effort required to take a pack of 501 arms and fit them on the car and that's what I've ended up with. I can now take a 501 arm and have it ready to fit on the BJ4 in about 2 to 3 minutes.

~~~~~

Let's start with comparing a fully modified arm against a partially modified arm and bulkhead



So on the left we have the arm as modified per the original post. The bulkhead on the left is unmodified. On the right we have the modified bulkhead and a significantly less modified 501 arm compared to the one fitted on the left. The important thing here is that the 'precision' modification is done on the bulkhead and not the arm.

~~~~~

The Bulkhead Mod :

Inserts...



Bulkhead...



Note: This photo was taken before I'd finished and there is a small ridge running top to bottom where the bulkhead has been filed away. You need to file this flush with the edge of the bulkhead otherwise the arm will bind on it. Note also that the edge of the filed area has been rounded off so it doesn’t bind on the wishbone.

~~~~~

The final part of the mod will require you to either modify the arm or the bulkhead. Here's why...



The issue is the gap between the pin and the arm. JConcepts... big, Tamiya... small. I looked at grinding down the bulkhead but I felt that the amount you would have to remove would potentially weaken it. You may disagree and if anyone out there has done it then why not share with the group ? I'm content to leave it at that as the arm mod can now be done so quickly with the bulkhead modified in the way I've done it.

~~~~~



So, the arm mod is now reduced to drilling the caster block hinge pin hole with an imperial 7/64 drill and ripping 1-2 mm from the arm to increase the gap between the arm and the bulkhead. This does not need to be a precision cut which is why it takes no time to do (with the right tools of course. God Bless Dremel ). There is no filing/fitting/filing/fitting/etc... as with the full arm mod above.

A couple of hints on drilling out the hinge pin hole.

• Put some tape on your drill bit so you know how far to drill. Use the pin for guidance.
• Be careful when you’ve been through the first hole and you going into the second. I found that the drill bit could bite in and you could be through the end stop before you know it. Then you’ll have to mimic the screw stop on the other side to stop the pin falling out.

~~~~~



One final shot of the bulkhead back on the chassis and that about wraps it up. I guess only time will tell if this has all been worth it but the 501 arms definitely look and feel like they should be stronger.

Regards,
Jon.

Faversham Off-Road Car Club

[Chequered Flag Racing]

Tamiya 501x front arm part # please & Tamiya stockist

broke 2 BJ4 arms last time out so I'll be modding mine

[ben]

Ive just done the mod on my S4 aswell. I dont think im ever gonna break a wishbone again

[Northy]

Who did it Ben?

G

[sparrow.2]

What do you guys do about the inner hinge pin? The hole in the Tamiya wishbones is larger than the Jconcepts pin. Not hugely but enough to have ugly slop.

[jimmy]

you got any more of that 3mm rod ben? can you get me a 'length' of it? gettin hold of spare shafts int always easy.

[sparrow.2]

Originally Posted by jimmy

you got any more of that 3mm rod ben? can you get me a 'length' of it? gettin hold of spare shafts int always easy.

I'll take that as a bit of a hint then

cheers

[Hairy Spider]

Wow, I started this thread a year ago yesterday. Happy Birthday Thread

FWIW since the mod was done on my car I've only broken 2 arms and to be frank I deserved it both times (Car vs Concrete) so I would have to say it was worth it. I broke way too many original arms for 'no apparent reason'

I've recently taken the mod one step further by taking an unmodified pack of 501 arms and replacing the bit in between by an unmodified 501 Worlds Edition . I'd still be intersted to know though what the current school of thought is on the BJ501 and what the most popular way to mod it is. Do you just mod the arms ? Do you bother with the bulkhead ? Did anyone modify the bulkhead to the extent that you didn't need to rip 2mm off the arms ? It looks from the recent posts that you guys are replacing the pins (The slop never bothered me. It was sloppy before I started and I was content with the knowledge that with 501 arms and 2 shock towers epoxied together that the front of my car was pretty much indestructable )

Anyway, Happy modding,
Jon.

[NSDie]

Using the tamiya hinge pin would require you to mod the hinge brace as well.

[B44&501xRacerEX]

Originally Posted by jimmy

Good stuff jon, I test fitted the arms when I got the 501X but never had time to put the arms on (and don't have my BJ4 at the moment) but I think these will be a great addition to any BJ4we as they are reet strong.

I gurentee that BJ4 will be stronger than ever.
I couldnt believe they fit that good.
I have yet to break anything on my 501x.

I have to tell the BJ4 owners at my track about this.

I wonder if it drives any different?

[sparrow.2]

Originally Posted by B44&501xRacerEX

I have to tell the BJ4 owners at my track about this.

I wonder if it drives any different?

It doesn't really drive that differently at all. You just get an additional hole to the outside to run longer shocks in layed down alot. Haven't tried this and not really sure if it would be any good, but technically it's an additional tuning option

[501X Driver]

Tamiya uses a 3mm hinge pin.
Not all the pins listed at 3mm are the same.
I was in a pinch and found that most of the Hudy tools that I use were made with a 3mm shaft and ground down to the 2mm allen head.
So if you have a worn out tool be sure to check the shaft for its size.
You maybe able to use it some day.
The replacement shaft from Hudy is about $10 and you get 3 long pins from it. So the cost is more but not real bad.
Good Luck

[scaramanga22]

Hi Guys,

i also did the 501x Mod on my BJ4.

The first A-Arms where modified to fit the original Bulkhead
and last 4 races with big impacts, but i have broken them by
trying backflips on our big jump.
They broke on the grinded, modified inner hinge pin holes.

After this, i modified the bulkhead to fit the new a-arms in original shape
and have no probs since this.

For the 3mm pins i use titanium in long axles from titan-concept.com,
cut them by a dremel into the correct length and the costs are about 5€
for the complete car.

have fun........

[tom_chang79]

So is the S4 arms a direct fit for the BJ4WE?