“Mad Dog Racer”

[Hcp22]

Hi guy’s, it’s been a while sins I started a building thread here at RC10 Talk. Not sins Drop Box stopped the possibility to link pictures… you can say that I’m a drop out… But now I will try to make a new attempt to make a new building thread. I usually stick to Kyosho, but now it will be in the Yokomo section for the first time.

I have sins long been thinking of picking up an 834B or two and build my selves’ a vintage racer. So I started sometime in April this year to scan for a couple of parts cars that would be the base of this project. And I hoped I would be able to pick up some new parts to…
But there was no such thing as picking up cars or parts when it comes to the 834B… And if parts surfaced, they was ridicules expensive, how about the yellow steering kit for the price of $100, or a sway bar at the price of $90, and the most horrifying was the rear axles that had a starting bid at $256, well nobody did bid on those anyway…




Then this car turned up one day in July and I felt a bit desperate. I was thinking “I need that car” and luckily I got it for a reasonable price even do I think as was screwed… In the end of the auction someone laid a higher bid that was redrawn. The same person increase his bidding 11 times with $10 each time, and it was the last bid that was redrawn… Bosting a friend’s action in that obvious way is a shame. But as I was a bit desperate for a car, I let it slide even if I had to pay double up…
This will be my base for the build of my racer.





The next 834B that suffice for a reasonable price that I wanted was an SE. I gave seller an offer that he refused sins it was up for auction, but 5 minutes after the action with no bidder I send him a new message. And this time he accepted my offer, so now I had two cars. When it arrived to Sweden I saw that it was in rely good shape. It always hard to tell how it looks under all the storage dust/dirt.





I have very little experience with Yokomo, I have only owned two YR-4 on-road and I still own one of them. So this means I have to learn a lot about Yokomo and especially the old 834B Dog Fighter

I quickly understood that Delta was a big third party hop-up producer in close cooperation with Losi family and Ranch Pit Shop that was the American distributor at that time as I understand it. The parts to have from Delta is the slipper, the rear shock mount kit, Shocks, hardened diff halves and if you are so lucky that you find the belt conversion kit. Delta also made a handful of different chassis and a few other nice parts for the 834B




Hot Trick is another company that mad some useful parts. Other is JG, CRP, BoLink, Kyosho and more.




And I will tell you already now, this will not be a project for the purist that like it “box-art” or that you can’t use re-re ore modern parts. I will use modern wheels and tires, modern electronics, Li-Po and brushless motor. This is an attempt to make racer with 35 years old race technology.

So let the fun begin

[a01butal]

Good luck to you, I will watch this thread with much anticipation and hope you are able to continue down the road to completing your new/old 834B transformation. Btw, that was my Delta belt drive conversion parts picture you showed and thought maybe you'd enjoy seeing a picture of it in actual application. Much luck on your journey, you have a really good start already.

[Dadio]

Looks like you have a good start already ! I'll be watching closely as I'm a bit of an 834b addict , I now have three , a shelf queen , a racer like your planning and one I 3d printed , and yes I agree the prices are insane !

[DennisM]

Nice Project Lars.
Regarding the rear drive shafts - If I recall correctly, You can use the HotDog rear drive shafts. They should have the same spec.

[Hcp22]

One of the first thing I had to do, is to try to read up on wat the week point’s is on the 834 is as I plan to race it. As I understand it, it’s the C-hubs and spindles up front that is fragile together with lower old arms (first gen). If you are looking at the C-hubs, you can see that they are fragile and one of the donor cars had a broken one when I got it together with a broken spindle. So I realize I need to find spares, the best would be to find C-hubs in aluminum. I guess that Hot-Trick made them back in the days, maybe Delta to. I know that Pargu is planning to make a re-run on his C-hubs, but I don’t know when.




At the rear its flexing arms that course you to lose your dog-bones. Yokomo’s solution was to mount some straps to holding arms in palace, and Hot-Trick sold wires that did the same thing. But Delta had an even better solution, they made an aluminum mount + some reinforcement for the arms. So that’s the kit to look for.




Another part, or I might say parts that is not that good is all off the outdrives, both front and rear. They are so soft, apparently Yokomo didn’t bother to harden them. So the ware is extreme, at least on those used ones I have seen.

I also need to figure out which hop-up’s I can lay my hands on, so I made me a wish list. I think I have found most of the parts. One of the parts I never thought I would found to a reasonable price is the Delta rear arm and shock mount #17781. But I did, only some axels ad spacers was missing as far as I know. Other parts I don’t think I will ever find is the front diff and the Delta belt conversion kit. But the belt conversion kit you can solve with a belt and a couple of aluminum pulleys.






Let start the restoring and the assembly of a racer

[Hcp22]

First thing is to have a chassis to build on, and to find the chassis I wanted from Delta is hard to find I believe. And I have to do it while I’m at my country house sins I have my little workshop there, can’t do any “big” job in the apartment. You have to remember that I’m married.




So the only thing to do is making your one.




I had some old CF (not quilted) from when I made a chassis for my old Tamiya SRB. I purchased a sheet (2x2 feet) from a guy in California that use to make porotype chassis for lots of RC company’s back in the 80’. Mostly it was pan cars chassis and he started his business back in -83 (DA Graphite). This sheet is a reproduction in the same way he did produce it in -84.




The first 834 chassis I cut out I did a layout mistake, I got the top layer fiber in the wrong direction. You want them along the chassis, not across. Whit modern quilted CF this is not an issue, you can cut it in any direction you want. Second time around I got it right




On this type of CF you have to super glue all edges around the chassis just to minimize the risk of splitting the CF chassis.




The faulty chassis didn’t go totally to waste, I made a top plate and the reinforcement to the rear arms. And I will probably cut out a few more parts yet.

[Hcp22]

The renovation of the gearbox was much easier than I thought it would be. Both boxes was in good shape on the inside. One of the boxes was a bit ruff on the outside, so that will the spare one.




I had already ordered new Kimbrough 32 pitch 46T Spur Gears (KIM116), Associated diff rings Steel (# 6625). New 1/8" ceramic diff balls, thrust bearing 3x8x3.5 and all the bearings.
I never need to use the new diff rings because it was no problem to grind the old ones with 400 and 600 grit paper and WD-40. The grove wasn’t that deep at all. The old spring washers for the trust bearing had to go, and was replaced with Thorp/Dirt Burners disk spring washers (#4439) to get a more sensitive and lasting adjustment. Kyosho have similar or maybe they are the same disk spring washers in their ball diffs for the Ultima, Optima Mid and I think the Lazer to. First, I was thinking to use a modern spring, but there is not room enough to install one.






One set of the outdrives was in decent condition, so I kept those even that I have new ones. But I want them hardened first, otherwise they will wear out rather fast, although I think the used on will be good for one race. I would say that this is one of the 834B week points when it comes to ware.






So now I only had to put it all together and after 5-6 minutes of breaking it in with my drill, it was rely smooth.




Both boxes had a slipper, Delta and an SE slipper. I decided to go with the Delta slipper sins my plan is to belt convert my racer. No, I have not found a Delta belt conversion kit, I have to make my own kit.






I also chose to replace the old 32 Pitch 46T gears with a brand new Kimbrough gear. Change all the 1/16 balls in the thrust bearing sins I couldn’t find a new one and grind the old washers. I cut out a new slipper pad from an HPI set (#115318) that also comes with a slipper spring. I also replaced the two disk spring washers to the spring in the HPI kit. Depending on the spring length you need a new 6-32 screw, either ¾ or 1” long screw. I used a 1” to the long HPI spring.








One thing I have wondered about is why Delta mixed imperial and metric in there hop-ups to a “metric” car as in this slipper? Yes I know Delta was made in the US, but still…. It’s so easy to mix up your screws and ruin your threads.




I kept the two gears nearest the motor, they were in good shape and had the steel axles. And I have got a set for spare, actually I have two sins I got an offer that I couldn’t refuse. This is the most critical of the gears, so easy to get a lose motor and ruin that gear.




The front is missing a diff, is only freewheeling with one-way bearings at the wheels. Kyosho had the same setup with one-way bearings up front on their Progress. Yokomo eventually made a front diff for the 834b with part number ZB-10D, but I think this is a rare upgrade and therefore hard to find.




Sins I don’t have a front diff stashed away I had to keep the old setup, only replacing the two inner bearings. I almost forgot; I also mad a little grove in the front axle for the set screw that hold the outdrive on the left side. The set screw makes nasty traces, making it difficult to slide on and off though the bearings.




To connect the gearbox with the front I will use a belt instead of the chain sins this was an option from Delta back in the days. This is pretty easy converting, all you need is Delta slipper, two pulleys and a belt. I used a 17T (S3M) pulley from 3Racing and a 453mm/151T/3mm (S3M) belt from Boom Racing. Depending on the chassis length you might have to go with 16T pulley. Those pulleys I got from 3Racing, I had to drill out the center hole on. But only 1 mm from 4 up to 5mm to fit the front axle and the Delta slipper axle.










I think this belt converting is a pretty neat upgrade for a runner/racer. I know there are many kinds of schools when it comes to renovating a vintage runner/racer ore shelf queen.
On one side we have those purists who want it to be box stock and only original parts. That is fine with me and I admire those for their patience.
I’m the type who tries to find out every trick in the book and modification they use to do back in the days when building my racers, and maybe ad a few tricks of my one. That means I search for all the hop-ups available, if I can’t find them I try to make them my selves or use reproduction parts. It was very common that races made there one parts and modifications. Frankenstein cars was also common, you used those parts available and built your own car. I did it my selves’ back in the days.

Then I also try to find spare parts that I know might break or wear out. The only modern parts I use is radio, servo, ESC, motor, wheels, tires and a few other things like silicon oil and so forth for practical resends. There is one other “modern” part that I use, but I come back to that later. Otherwise I try to stay true to the model and time period as I possibly can.

[Dadio]

That's all looking really good , what belt pitch and length are you using ?

[Hcp22]

I used a 17T (S3M) pulley and a 453mm/151T/3mm (S3M) belt

[Dadio]

Thanks , might have a go myself

[naushad]

As usual, excellent stuff from a veteran racer!

[naushad]

I do wonder how that fared without a tensioner system? Placed like that there is no way of adjusting tension - unless you change belt length. At least with the chain you could remove/add links to tune. I'm sure you've seen the homemade tensioning systems in some 834b rigs...

Good luck to you, I will watch this thread with much anticipation and hope you are able to continue down the road to completing your new/old 834B transformation. Btw, that was my Delta belt drive conversion parts picture you showed and thought maybe you'd enjoy seeing a picture of it in actual application. Much luck on your journey, you have a really good start already.

IMG_1945.JPG

[Hcp22]

Kyosho’s red CB-88, FM-71 and #1886 was the most popular upgrade for off-road cars back in the day. Yes, there was others like the shocks from Delta, Losi, Associated and a few others, but I would say that Kyosho was the most popular of them all early on. So when I look at a modern shock, nothing much has happened more than “big bore”.




I have a substantial lot of Kyosho’s red shocks, mostly CB-88’s. The problem with this old 88’s is that they leek like a drainer and you can’t replace the O-rings. You are supposed to replace the whole bottom plug where the O-rings are imbedded. And that’s a spare part that is rely hard to find. I have been running old red shocks on my vintage Tomahawk sins the first vintage race 2012, CB-88 at the rear and FM-71 at the front. But as you can see in the picture, they are leaking… Some might say “that’s vintage for you”… Humpf…




This means that I will go with “modern” Kyosho shocks, not big bore, just a regular 10mm bore as the red ones. At least you are able to renovate those so they don’t leak. An alternative would be Kyoho’s gold shock sin they just have been re-released.




I have used the Delta shock tower/arm mount kit that I was lucky enough to get hold of at the rear. I also made new rear arm stiffener out of the faulty chassis I made.




I have use the re-re Scorpions wheel axles SC233 and the 12 mm hex driver set SCW020. This is a tip from “Dadio” that I picked up from his thread “Yo-clone-oh Dogfighter”. This gives you a change to run 2.2” modern wheels. To do this you also have to replace the rear bearings from 5x10x4 Flange to 6x10x3 sins the Scorpion axle is 6 mm and not 5 mm as the Yokomo. And you have to shave off 0.3-0.4 mm on the inside of the hex drive to make it fit nicely. This also means that you have to monitor those bearing with this increased load due to the longer axels on high bite carpet/AstroTurf tracks. Had that problem with my Tomahawk, the flange broke at the rear outdrives a few times for me.












The front has been a hard case to solve to my liking sins I wanted a wider front. I haven’t solved it quit yet, but almost. The Idea is to use the upper arm as the lower arm, but I have to reinforce it first so you can attach the front shock/shocks (depending on setup). An alternative is to use a Pargu upper arm in aluminum, but as I said: I’m not done thinking and testing yet.




So I came up with temporary solution involving a “modern” part from a +20 year old Kyosho Pure Ten Alpha. The part I will use as a temporary solution is the front suspension arms, those have almost the same width as the 834 upper ones. And this together with some 35 year old Optima parts, C-hub and spindle (period correct design). To make this Optima spindle to work with the 834 axels and one-way wheel hubs you need two different sizes of bearings, 2 piece 5x10x4, 2 piece 5x10x3. You also need a few 8x10 shims to get rid of a small gap sin there are no 3.6mm thick bearings. The good thing to use Optima parts, is that they are still available after re-re. You also need new hinge pins, I used some from HPI. I have also carved a bit on the Alpha arms to get them to fit the bulk head and a tad on the C-hub as well.






I also need new dog bones, if my calculations is correct… Thorp #4940 Dog Bones 67mm (cc pin to pin) will fit perfect. But for now I don’t know sins they are in transfer from US to Sweden. When I swop to the 834 arms I might have to find a 1-2 mm or so longer dog bones.




Another trick back in the days to increase the width of the 834 is to swop sides of the one-way wheel hubs. This alone will give you a 12mm wider front.




Hot Trick have a tie-rod kit #008Y to replace the upper arms. I will use this solution, but I won’t be using that kit even if I have one lying around. I used old tie-rods from Thorp, 5.8 mm blue ball ends I had. The Hot Trick uses two tie-rods on each side, but I will only use one.








I made a front shock tower from that faulty chassis I made. This allow me to go the Hot Trick way with dual front shocks instead of the original mono-shock. My brother got me a 3mm bent aluminum sheet that I will try to make a tower out of it later on. But he also made me a 20x20 and 65mm long aluminum angle that I will attach to the tower and chassis. This to prevent the bulkhead to become torn of sin it’s only two M4 screws holing it to the chassis.






I replace the old steering assembly to one in aluminum from Hot Racing. Maybe this isn’t period correct, but the setup is the same as original, and I’m good with that. The only thing to do on the steering is some adjusting trying to lose some bump steering

[DennisM]

It´s coming along nicely - thumbs up

[Hcp22]

It´s coming along nicely - thumbs up

Thanks Dennis