R compared to RD frames for Vladislav

[85snowdog]

Rather than run the Mack grille thread completely off the tracks . I thought I would start something that Vlad was wondering. And I find very interesting. 

Vlad had a good point about the differences in the frames between R and RD. We had talked about it before on a different thread,  but I couldn't find it. For some reason the search tool doesn't work very good for me. (could be me ) . 

Anyway , here is what Vlad was wondering on another thread.

Also a mystery (I try to be short) is chassis differences between R600 and RD600 frames. They have different rail heigth (the same is between RW600 and RW700) What does that mean? That means that the rail lower edge seats on the front spring brackets . The cab mounts are attached to the rear ones of those. If so the upper edge of the rail must be closer to the cab floor than with narrower rails. But in fact it looks like it doesn't. This means that the sizes are compensated somewhere. That could be done by different brackets which difference you can't see by their look, or by higth of the front axle springs or by any other way.

After seeing this I thought It was a very good question. Something has to be different . Fortunately , I'm not very good for much , but taking pictures. 

So I have some comparisons of R to RD to show how it was done.

It appears that all dimensions and frame drilling was done from the top of the frame rails. The extra inch and bit are on the bottom side of the frame.

The first pics are the spring hanger bracket on the R600. 

The second is the spring hanger bracket on the RD600. you can see the top space is the same and bottom space is larger on the RD. The brackets appear to be similar also. They also have the same number 51QKA233A

On the back side of the bracket is a shoulder that almost touches the under side of the RD frame rail, but is at least an inch away from the R frame.I think this explains how they accomplished using similar parts on different frames.

 RD frame 

 R frame 

I also looked at the rear cab mount. It appears the same . Everything is done from the top of frame . The spacing on the bolts for fuel tank brackets/cab mount bracket was 5 1/2 inches. Same on both trucks. Just bigger space under the bracket on the RD frame. 

RD frame 

 

  R Frame 

 

 

 

 

[Vladislav]

Wow!

Keith, many thanks for the pictures and explanations. Actually I had both R and RD chassis but the RD one was partly dismanteled so I couldn't relate everything between them. Also I didn't pay enough of attention to the matter at the time and later we parted out the RD chassis completely so now it's late to. The gap between the lower rail edge and the rear spring bracket is something new to me. For some reason I thought the bracket supports the rail by its bottom. Also my RD chassis had different rear brackets cast of iron (it was RD690 of 1990 or so with a square hood) and my R688 has them alu and of a shape you represented on the photos. Big difference concerned front front spring brackets which were almost different from R688 having big tow eyes in the lower part, almost below the rear edge of the frame rail. I saw brackets which looked similar but used on early R-model chassis. But it was difficult to judge from the pics since those early trucks could also be RD. BTW what was the year a RD model came into production? Were they of 60's and 70's years or started in 80's ?

Ok, now it seems mostly clear of the way of installing taller frame rails at the front. Just wonder what was at the rear? Did the bogie stand (if Camelback) just got an upper position between the rails? I think if the spring packs don't meet the rail sides no matter how low rails take place between the springs.

Worth to point out my actual matter of interest is a search for a pair of good rails for my R-model. The existing set is almost unusable due to an accident in the past. I looked for solution purchasing new rail sections from PG Adams but wasn't satisfied with match of bend radius between the web and flanges. And also I hate to have a weld seam right in the middle of the chassis or large inserts inside the rails. I said I had a set of really nice RD rails which are tall and really thick. But that game with front spring brackets would put me off the originality again. And there's a point aside of that. My original rails don't have a chassis number stamping. And that is marked in the paperwork. So what I need is clean rails. Deleting such stamping in my country is a crime. That follows to complete regestry cancellation if found.

Edited May 9, 2020 by Vladislav

[85snowdog]

I hope It's helped you a little, and hasn't added more questions. 

I will do some checking on the front spring brackets and report back. 

[JoeH]

My 88 RD690S front spring hangers are taller than my 1995 RD688S.  '88 has 20k front with 4 leaves, 44k rears & lift axle.

95 has 18k front with 16 leaves, 44k rears & lift axle.

Different front tires, but the '88 sits roughly 6 inches taller at the front.

[Vladislav]

7 hours ago, 85snowdog said:

I hope It's helped you a little, and hasn't added more questions. 

I will do some checking on the front spring brackets and report back. 

Very appreciated.

Please also check the bogie stand position.

[85snowdog]

 I have some more pics for you Vlad. I have to apologize in advance . I think these add more questions than answer them.

I forgot to mention in the first post. The R 600 is a 1988 with a 14,300 # front axle . The RD600 is a 1986 with an 18,000 # front axle. 

You will see by the pics that both front spring brackets are very similar . Even the size of the frame at the front of the truck is close to the same .

 

RD first pic, R second pic

RD frame

R frame 

 

 

 

 

 

 

 

 

 

 

Edited May 11, 2020 by 85snowdog

[85snowdog]

The best I could do for the bogie stand is comparing an RD with 38,000 # to an R with 44,000# . The R frame is the R 700. But the frame hight is the same as my R600. 

This is where things get muddy. At the front of the truck the extra inch is on the bottom of the frame. On the back ,the bogie stand is kept on the bottom, and the extra inch of frame is on the top. Unfortunately , it doesn't make sense to me. 

First pic is RD

 

Hopefully , this helps . Its unfortunate you can't use your RD frame rails because of the V.I.N number. It sounds like its in good shape. 

 

 

 

Edited May 11, 2020 by 85snowdog

[Vladislav]

Upps...

That's what has me scratching my head. And seems like it has a tendency to spread like infection.

My R688 is 1988 and has both front and rear brackets similar to both of your trucks. The axle is FAW537, 12000# if I'm not wrong. # taper leaf front springs and rear brackets cast of aluminium.

The pics are what my RD690 donor truck had. Difficult to figure all original specialities since the truck was modifyed by installing of a front drive axle and the rears put almost below the main rails as a section of a DM (judging by the rail heigth) chassis. As you can see the rear brackets were generally similar to R-model style but slightly different and cast iron. The front ones were completey another story. The hood attachment was also another but that makes sence since it was for a newer style square hood. Now seems it worth to me to measure the heigth of the frame rails at the front and relate to your figures. So far I expect the same range figures but it's a guess. The rails are separated and stacked aside a barn. So very easy for observations.

You're right. Those RD rails are absolutely decent. That was a double frame and the truck spent the most of its life at extreme North with about no public road driving being an oilfield equipment carrier. So no salt and probably not much driving at all. But the VIN stamping doesn't suit my needs and the front spring bracket differences adds salt to the dish.

[85snowdog]

Maybe on a positive note. Maybe the bolt pattern is similar to your R688 ,even if the brackets are different. 

[Vladislav]

7 minutes ago, 85snowdog said:

Maybe on a positive note. Maybe the bolt pattern is similar to your R688 ,even if the brackets are different.

Looks like they are. And the rear ones also. I was wondering the cab mounts position but after you investigated the rail goes down there that's not a problem either. The problem could be the rears since mines are Neway and the lever brackets fit to the rails by the lower flange. I suppose RD's with Neway are a seldom view if any but that story must have working solution in RW700.

[85snowdog]

From all the work I have seen you do. I'm very sure you could figure that out .  

[Vladislav]

Thank you for the credit

My current option is using a pair of rails my second R holds on. Those are stampless and exactly the size I need. But they aren't really nice at the rear end, have some cracks over the Neway brackets. Good thing the cracks are in the web not in the flanges so I hope I would weld them up with no issues in the future. Another matter is I'm way from being excited parting out my only complete and running truck. I will do if no other option is found to the moment. But I also figured I need some other big jobs done such as the engine and two big chassis crossmembers. Also the cab interior and wiring are on the list. So now the plan is to provide as many of works as I can aside of the frame rail story. And when 90% of the components are ready I'd part out the truck to get the rails off, fix/blast/paint them and start assembling everything back together.

A trouble to find such rails is they're quite long for an avarage R-model. 220" wheelbase and 60" Canadian spread. From what I figured out there were not many American R-model highway tractors with sleepers and such  long wheelbase as a follow.

[85snowdog]

It sounds like you have a plan for going ahead.

I noticed something in your picture that triggered my curiosity . 

On the inside of the front spring bracket, are  some tabs that a cross member bolts to . I thought it was very far forward for the front of the engine. It didn't seem right. 

So my curiosity revealed that one reason for different front spring brackets is the Radiator that is used in the truck. 

On both my R and RD 688. The rad goes down beside the front spring bracket ,with not a lot of extra room. The rad is supported at the top side of the frame above the spring mounts.

On a RD 685 with a rad that allows a driveshaft from the engine crank. The rad doesn't come down as far, and we see a different rad, and rad support cross member is bolted to spring brackets. 

This , at the end of the day isn't very important . But like you said , the little details can be very interesting. 

 

This is your pic . 

This is outside of RD685 ( 1985 ) Looks like similar bracket to yours 

 

Shows from underneath . the same bracket as in your picture. Just opposite side. 

 

This shows the rad on RD688 .Rad goes down beside spring bracket. 

 

[Vladislav]

Wow!

I can say you digged out a very interesting detail. Alastair must be excited

Seems like you're almost right. My R688 of 1988 has rad sitting lower in the chassis being attached not almost the way you described yourth (I suppose you just didn't figure those points completely) but on a pair of brackets which are a thick bent still bolted to the inner side of the front spring brackets. They're not at the top of the frame rails but just a lil bit lower. Actually I don't expect to see anything else on your R and RD688 but I can never be 100% sure.

My RD690 you shared a pic of the front bracket of indeed had a different rad which seated higher off the frame. It was not exactly the same style as in your truck but also had a pair of legs it standed on the crossmember. Actually there was a rad support bracket the legs were attached to. You can see it hanging down in the picture when the truck was still looking as a truck. The crossmember also holded the front of the engine by a kind of shelf welded to its inner (rear) side. The previous owner stole the engine to put in his Freightliner so he took the crossmember off for the install. The rad bracket was bolted to the front (face) side so it stayed hanging on the rad which occured laying on the front frame rail ends.

Of other interesting things I found out RD690 rails kept original holes where the bolts were holding Camelback stand. From the pattern it's seen that the stand was in the lower position i.e. the excessive rail heigth was put up. Still a question to me. Currently I have a thought on the matter but need to observe the frame rails which are laying along a wall of my shed to possibly get the proof. Will share as soon as i do.

[Whiskymack]

12 hours ago, Vladislav said:

I can say you digged out a very interesting detail. Alastair must be excited

Sad to say I am! I've followed this thread with interest although I'm a bit out of my depth when it comes to frame depth. It is interesting to see how engineers managed to get standardized parts to fit not standardized frames with spacers and repositioning but it must open a whole can of worms when it comes to rebuilding with donor parts.

I had noticed the difference between the frame horns before. The ones on the 88 R and 86 RD go on the outside of the frame rails whereas the ones with the towing eyelet at the bottom go on the inside of the frame rails and I believe were an earlier design. I think they stopped using them on the standard R model around about the time that the corporate bumper came in although they kept them on the U series for a few more years and you can see cutouts at the bottom of the corporate bumper to access the towing eyelets. I've neverseen these cutouts on an R. Before the corporate bumper, the eyelets were below the bottom edge of the shallower bumper.

The radiator set up is also a whole topic in itself. Keith pointed out that the radiator mount bolted to tabs on the eyelet frame horns. I think that the engine sat on a cradle which bolted to the back of this mount. When the externally mounted frame horns came in the radiator mount was a kind of wide flattened u shaped crossmember which looks like it bolts to the inside of the frame rails possibly using the same bolts that attach the frame horns. Again the engine was held in a cradle that bolted to the back of this. In both cases the radiator sat quite high.

In the Econodyne era the R600 got the tall radiator that dropped down between the frame rails and was held by brackets on the inside of the rails. The engine was held in an asymetrical u shaped crossmember which was mounted behind the radiator. I'm not sure if this was all to do with introduction of CMCAC.

I didn't know that the eyelet horns and short radiators were still beng used in 1985. Was a 1985 RD685 still Maxidyne powered with no CMCAC and in that case did the non air cooled Maxidyne 675 stay in production alongside the Econodyne range?

This also leads me to start asking questions about the R700 but I'll open a new thread rather than drag this one too far off topic.

 

[85snowdog]

7 minutes ago, Whiskymack said:

I didn't know that the eyelet horns and short radiators were still beng used in 1985. Was a 1985 RD685 still Maxidyne powered with no CMCAC and in that case did the non air cooled Maxidyne 675 stay in production alongside the Econodyne range?

Yes,  the 1985 is a maxidyne with no CMCAC. I believe they were in produced till 1987 or 1988.