SRB rear arms

[pleiku68]

Just received an auction from ebay...Ineresting set of rear arms..We have all seen the nylon double bearing one, RCH, MIP or who ever..TOO long ago to remember or care..BUT I have done probably 30 SRB's start to finish and bought many, many, parts above and beyond that...Today I have seen something I did not know existed...Ok, so I am probalbly going to find out I am the only one in the club who has never seen these before...Cast Aluminum rear arms with double bearings.THe rear arms are not marked 1,2, 3 or 4 like Tamiya manufactured..These are not machined as I can see right now but I will know better tomorrow when I take them out of the vib finisher..Right now I will assume them to be RCH because of the front ams that are with the car...

 I often wondered who made the light aluminum front trailng arms..Always thought is some guy in Oz but I have a NIP from RCH..Another first for me..Actually not a first I have a couple of sets but never new for sure who manufactured them..If this has any interest other than to me I will post a picture in my show room tomorrow..Still can't post to the forum..I believe it to be magic..regards jerry

[T.C~Tamiya]

Hey Jerry

You don't mean arms like this do you ?

If so then these are standard Tamiya (early version) rear arms, also the front arms from the same era cars were thinner and more light weight than the later versions.

 

[pleiku68]

Your the man..Thats what they be...Wonder why they stoped with the duel bearings???Can't believe I never had a set with all the ones I bought through the years...Thanks TC now I can sleep...lol jerry

[Shodog]

I don't know if it was the earlier versions or later versions that had these.  My NIB scorcher which is fairly early with flat headed screws and screw in front uprights has the single bearing rear arms

[T.C~Tamiya]

I've only ever seen these double bearing arms on early cars, for example, cars with black bumpers, old style gearboxes, no breather holes in the clear parts, screws in the shock towers etc. So I'm guessing they are the early type.

I think there might have been a cross over point when the SRBs came with a mix of early and late parts, like the single bearing arms & the shock towers with the screws.

If anybody has a NIB black bumper model it would be interesting to know what kind of rear arms it's got.

[pleiku68]

I have checked all my build manuals..My Sand Scorchers go back to 1979..The Rough Riders to 1980...Every manual show the double bearing rear arm but never mention the second bearing. Probably why this has been overlooked....ONLY one is used in the build sheets...Every Super Champ build manual has the single bearing model pictured...Does anyone have a Manual prior to 1979 that show the physical installation of the Second Bearing. I bet they don't...This car did have the screws in the shock towers but so does my 1979 Scorcher Manaul...Very courious and have never seen this posted on the TC site before...Where is Scorchio when you need him..lol.

[Bigwheels_inc]

i would have thought that these were the later type arms as there stronger and with the double bearings would cause less friction

and surly why would they go from double bearings to single ones ? ..... from what i know of tamiya it seems if its over enginered they seem to think who cares as long as it works !

in other words why go for 1 bearing when the part works as is with 2

Pete

 

[T.C~Tamiya]

I still think they're the early type based on observations made from the 20 plus Sand Scorchers I've bought, Black bumper models I've had always come with the double bearing arms, later grey bumper ones always with the single bearing arms.

[pleiku68]

No, all the old manuals show the double bearings, 1979 and 1980. Even the XLT shows double bearing...Seeing that the RR came out in Nov 79 and the SS maybe very early 80 or late 79..There were no kits before that to use this rear Arm..Again my guess is they changed the arm but not the manual.....The Newer Super Champ is the only manual to show a single..I think you will find out that these were probably only used in the Rough RIder early kits...and because the real bearing is not enclosed with a C clamp they would ride out causing problems..I can see how even the best shimmers would have a problem keeping the rear bearing in place..Unless they knew of the hot exacto knife trick for shimming bearings..The after market nylon units were a very tight fit so the rear bearing would stay in place..But Its all conjecture now but I bet there are not 5 sets in the whole club with the double bearings. I have a set and TC has 1/2 set..lol is all I have seen....If they were new there would have been a vast number of replies... like I got than one Bloke are you nuts...Lets make this interesting...The first member to send me a pictue of any SRB, NIB, other than a Rough Rider, the earlest SRB, with the double bearing REAR arms still in the bubble. I WILL PAY PAL $50..Now if these are old at least one member with an NIB Sand Scorcher, XLT or Super Champ has them in their kit...No trick photos..I will have Simon check for auththenticity....lol jerry

[Bigwheels_inc]

I have a set on my runner sand scorcher and i know shodog has a set

OK there not new but thats 2 sets + jerrys

Pete

[Shodog]

I have a used set on one of my rough riders but my NIB scorcher has the single bearing. 

[pleiku68]

That about how if  I believe this will turn out..I think these will only show up NIB in the Rough Rider kits...Just a gut feeling...Well were up to 2 1/2 sets..Yours, mine and TC's...lol jerry

[T.C~Tamiya]

I've got about 10 pairs of these so I don't think they're all that rare, I reckon somebody somewhere will have a NIB Scorcher with these arms in the box. I've had plenty of used Scorchers with the double bearing but of course I couldn't prove that they didn't start their lives as Rough Riders.

[pleiku68]

I've got about 10 pairs of these so I don't think they're all that rare, I reckon somebody somewhere will have a NIB Scorcher with these arms in the box. I've had plenty of used Scorchers with the double bearing but of course I couldn't prove that they didn't start their lives as Rough Riders.

I tell you TC they must all be in the UK...These guys have been my life for the past 7 years since I retired..I just shimed up my set..They are unbelievalby smooth...For those that don't know the Hot Exacto knife trick for shimming bearings..Its easy..cut a one square in piece of poly pro from a small parts bags..Usually 3 mills thick..force the bearing between the polly and the hub...Heat the exacto to red hot..touch the center and the plastic dissappears..trim around the hub..Learned this from a guy that was may age 20 years ago..been doing it ever since..works great on SRB gear case..

[T.C~Tamiya]

I could be totaly wrong but this might be a NIB Scorcher with the double bearing arms, from looking at the photo it seems to have the old style gearbox, the light weight front arms and the towers with the screws, but... the rear arms are too hard to see at that resolution

I'll email the owner to see if he can give any more info.

 

[pleiku68]

I could be totaly wrong but this might be a NIB Scorcher with the double bearing arms, from looking at the photo it seems to have the old style gearbox, the light weight front arms and the towers with the screws, but... the rear arms are too hard to see at that resolution

I'll email the owner to see if he can give any more info.

 

 

Yup that is one of  the older kits...Be interesting to see the rear arms..A photo of the bubble showing a rear bearing will some one $50 Pay Pal..Now I just have to find out one way or the other..Tamiya does not always up grade and over engeenier..They went from Steel U joints to brass..Why did they ever do that??? Ah, they were not selling enough replacements. Thanks for looking into this..TC..Regards Jerry...lol

[DJTheo]

Very courious and have never seen this posted on the TC site before...

Not even very old mate LOL [] http://tamiyaclub.com/CS/forums/thread/176690.aspx 

http://tamiyaclub.com/CS/forums/thread/160034.aspx

Cheers 

[DJTheo]

[Tamiya does not always up grade and over engeenier..They went from Steel U joints to brass..Why did they ever do that??? Ah, they were not selling enough replacements. Thanks for looking into this..TC..Regards Jerry...lol

Where did this happen??? The 3 first SRBs had brass u-joints and the later Super Champ had steel ones.

Cheers 

[pleiku68]

I knew that right after I wrote it...Black bumpers before gray...Brass before Steel.[]..but I decided to leave it and let an astute mod make the correction..Tamiya does not always up grade and over engeener.t..The tie wraps I really hate..All my hybrids, SC, that I did keep the original Tamiya cage..I cut the Aluminium and drilled new holes so I could us the clamps......OK..plastic tie wraps on the Super Champ vs nice metal clamps on the first three for the roll bar, improved?? Overly Engeenered??.[].Now that said I am trying to find the preivious link you mentioned..The one you posted brings me to Birdys SS project..Unless its hidden deep inside I can not find it. God Theo now I have hijacked my own thread..LOL. regards from sunny Florida jerry

[KEV THE REV]

I have a pair of SRB rear arms with double bearings, but all of my collection of 7 SRB's have single bearing rear arms.Strangely though my SRB mauals all show thw double bearing illustration for the rear arms but only one bearing being fitted,with the exception of the Champ manual which shows a single bearing type rear arm illustration on page 3 step 3 ,but on page 4 step 4 the illustration changes to show a double bearing type arm again ,but only one bearing fitted. On the subject of manuals, has any body got a Brat manual which shows the Brat moving from right to left on the cover, as opposed to the usual left to right pic. ?.I have both types of original manual , and apart from the cover being different ,some of the pages show different illustrations at various stages throughout the manual, just wondering if anyone else has seen this  []

[DJTheo]

Now that said I am trying to find the preivious link you mentioned..The one you posted brings me to Birdys SS project..Unless its hidden deep inside I can not find it.

On his 3rd sentence Birdy writes "the chassis i a MK1 double bearings in the rear.. screws in the front shock towers to attach the suspension springs.."

Cheers 

[terry.sc]

From an engineering point of view there is a very good reason for

Tamiya to stop using twin bearings, which they would only come across

when they were built and being run by non experts. Due to the simple

suspension design twin bearings would support the axles best, but for

it to work without binding the UJ needs to be positioned exactly in

line with the swing arm pivots. If the UJ isn't attached in exactly the

right place on the axles the twin bearings will put large side load on

the UJ as the twin bearings support the axle, which will not be in line

with the UJ.

There is also the problem of what happens when you

hit something with a rear wheel and bend the rear swing arm. The axle

again will no longer be in line with the UJ pivot and again will cause

the rear drivetrain to bind.

By only fitting one bearing in the

swing arm it allows the axle to move about. It can stay in line with

the UJ so the drivetrain doesn't bind up and cause premature wear.

Using

one bearing also means if the wing arm is bent you can shim it up to

push the arm forward and keep the wheels straght. If twin bearings were

used once the arm was bent you would be stuck with permanent toe out on

the rear.

[T.C~Tamiya]

From an engineering point of view there is a very good reason for Tamiya to stop using twin bearings, which they would only come across when they were built and being run by non experts. Due to the simple suspension design twin bearings would support the axles best, but for it to work without binding the UJ needs to be positioned exactly in line with the swing arm pivots. If the UJ isn't attached in exactly the right place on the axles the twin bearings will put large side load on the UJ as the twin bearings support the axle, which will not be in line with the UJ.

There is also the problem of what happens when you hit something with a rear wheel and bend the rear swing arm. The axle again will no longer be in line with the UJ pivot and again will cause the rear drivetrain to bind.

By only fitting one bearing in the swing arm it allows the axle to move about. It can stay in line with the UJ so the drivetrain doesn't bind up and cause premature wear.

Using one bearing also means if the wing arm is bent you can shim it up to push the arm forward and keep the wheels straght. If twin bearings were used once the arm was bent you would be stuck with permanent toe out on the rear.

But the UJ finds it's correct position on the axle naturally when the parts are assembled, I don't really see a way of putting it together wrong which would cause binding, and if the rear arm gets bent so badly that it causes the the UJ to bind then it ought to be replaced anyway.

My point being, When they changed from the double bearing to the single, I don't think it was because Tamiya found the double bearing arms to be problematic from an engineering point of view as you suggest, it was probably just more economical to make the single bearing ones (in my humble opinion).

[pleiku68]

Ok here is what I do not understand..Tamiya never, ever mentioned a second bearing in any of the build manuals that I have and I believe I have all of  them starting with 1979..Now every build manual except the super champ shows the rear arm with a place for a second bearing. I am talking the Rough Rider, Sand Scorcher and XLT manuals all show the second bearing arm...So they made a unit that you could put a second bearing in but never mention it in the instructions...Tells me that the Original Car which I believe to be the Rough Rider after being assembled had some problems..Too late to make new arms so just keep the instructions as is and don't ever, ever, mention a second bearing. A secret still locked away with the formula for Gator ade.Interesting enough around 1979 a few Japanese people were kidnaped and taken to North Korea..These may have been the engeeniers with the secret.[]....If I am wrong and someone has a build manual showing the installation of the second bearing please advise.This would settle the whole issue with me...Also the original arm is a lot more slopy than the super champ one when you only use the one bearing because the rear hole is alot bigger..Why did not some one complain when the kits were two bearing short!!!???  or did they have two extra bearing but no instructions on where to put them....

[Shodog]

It turns out I have two sets of the double bearing arms.  Here's my take.  One of my Rough Riders has a slightly bent axle and when both bearings are in place it binds really badly.  we all know how weak those axles are so I think they eliminated drilling the hole on the inside