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Busstom
Samba Member
Joined: November 23, 2014
Posts: 3841
Location: San Jose, CA
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 Posted: Fri Sep 14, 2018 7:19 am Post subject: Rack-and-Pinions: A-Arm or VW Beam-Type? |
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I have three questions, really…
So, A-Arm or VW Beam-Type: What are the differences? Visible appearances are somewhat obvious. But pretty much every Internet descriptor I’ve found states it like this: A-arm = front steer, beam-type = rear steer. Presumably, front steer refers to the spindles being actuated by the tie rods in FRONT of the spindles/axle, and rear steer, well, the rack is BEHIND the beam and actuating the spindles from the REAR of the spindles. No? Please set me straight, and why does it matter?
Secondly, what does “tatum” refer to? This term seems to be referenced strictly with the A-arm racks, but I don’t understand why. What does tatum mean, exactly? A manufacturer of one type of rack?
Lastly, is a 1.5 to 1 ratio going to be a problem on the street? This thread speaks briefly to it, and seems 1.5 to 1 is better for street https://www.thesamba.com/vw/forum/viewtopic.php?t=88162&highlight=rack++pinion Just looking for opinions and effects of one over the other.
Thanks guys (and gals)!
Last edited by Busstom on Fri Sep 14, 2018 5:58 pm; edited 1 time in total |
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pullstart
Samba Member
Joined: August 23, 2016
Posts: 599
Location: Middleville, MI
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| Posted: Fri Sep 14, 2018 4:42 pm Post subject: Re: R & P: A-Arm or VW Beam-Type – the differences. |
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How much money do you want to spend, how much travel do you need? You can find a ton of well built beam type front ends that perform well in many different terrains. And then there’s A-arms, and travel is virtually unlimited but if you control what you have with good shocks you might be surprised how smart the beam is.
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4 seater Appletree buggy, road legal with 002 IRS, 3x3 Appletree kit, 6" over Dan's beam with 10" towers and Fox 2.0 shocks, '00 Subaru EJ25 with KEP stage 3 clutch and KEP adapter plate.
my build page: https://www.thesamba.com/vw/forum/viewtopic.php?t=662104&start=0 |
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Busstom
Samba Member
Joined: November 23, 2014
Posts: 3841
Location: San Jose, CA
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| Posted: Fri Sep 14, 2018 5:25 pm Post subject: Re: R & P: A-Arm or VW Beam-Type – the differences. |
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Sorry, I think my post was unclear: I led off in the title with R & P, as in Rack & Pinion.
So, all of my questions are about rack and pinion steering gears, not suspension design types...I'm fully versed on those. I'm looking for more education on rack-and-pinion types and their associated terminologies. So with that in mind, I may get more replies about steering racks. I was a bit surprised by all the views without any replies, now I see why.
For what it's worth, this is in my '64 Bus, which actually has a narrowed Bay beam with BJ spindles. And I already have a Saco rack, it's a 64-1000 Tatum. I bought it some 15 years ago for this custom build, but now I'm questioning why I bought a so-called A-Arm rack and not a Beam-Type rack. Again, I say that because that's how everybody describes them in their ads.
So really, if an expert or anybody who knows the answers to my questions above, specifically related to R&P steering gears and nothing else, that would be cool.
Thanks again. |
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Fenix
Samba Member
Joined: October 05, 2016
Posts: 468
Location: St Louis
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| Posted: Sat Sep 15, 2018 6:05 am Post subject: Re: R & P: A-Arm or VW Beam-Type – the differences. |
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| Busstom wrote: |
Sorry, I think my post was unclear: I led off in the title with R & P, as in Rack & Pinion.
So, all of my questions are about rack and pinion steering gears, not suspension design types...I'm fully versed on those. I'm looking for more education on rack-and-pinion types and their associated terminologies. So with that in mind, I may get more replies about steering racks. I was a bit surprised by all the views without any replies, now I see why.
For what it's worth, this is in my '64 Bus, which actually has a narrowed Bay beam with BJ spindles. And I already have a Saco rack, it's a 64-1000 Tatum. I bought it some 15 years ago for this custom build, but now I'm questioning why I bought a so-called A-Arm rack and not a Beam-Type rack. Again, I say that because that's how everybody describes them in their ads.
So really, if an expert or anybody who knows the answers to my questions above, specifically related to R&P steering gears and nothing else, that would be cool.
Thanks again. |
Most say they can be mounted either way by reversing gearing, but the ones I’ve seen specifically labeled as beam-style also have VW in the description as well. The main thing would be the movement of the rack when the pinion is turned. Turn a front steer to the right it will move the rack to the right. Turn a rear steer to the right and it will move the rack to the left.
Tatum is a brand Tatum Motor Sports, sandbars and trouphy trucks. Saco resells/lisenced or copied/referenced a design most likely or Tatum manufactures it for them. The 64-1000 is a VW based sandrail specific rack with 1.5:1 ratio. So not exactly sure why you feel it’s a front-steer setup. Look up Tatum 64-1000 you should get hundreds of hits from e-bay, Amazon, and all the buggy and Baja parts resellers. |
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Busstom
Samba Member
Joined: November 23, 2014
Posts: 3841
Location: San Jose, CA
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| Posted: Mon Sep 17, 2018 12:14 pm Post subject: Re: R & P: A-Arm or VW Beam-Type – the differences. |
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| Fenix wrote: |
The main thing would be the movement of the rack when the pinion is turned. Turn a front steer to the right it will move the rack to the right. Turn a rear steer to the right and it will move the rack to the left.
<snip>
...not exactly sure why you feel it’s a front-steer setup. Look up Tatum 64-1000 you should get hundreds of hits from e-bay, Amazon, and all the buggy and Baja parts resellers. |
Thanks Fenix, that makes sense. Based on my steering design, I've got the right R&P gear. I know it sounds crazy, but now that I'm digging back into this project after so many years, and looking on the Web at those product descriptions, I was beginning to wonder why the distinction, and why I chose what I did (I've got the 64-1000T front-steer version).
If you look at these links, you can see that Saco makes both a 64-1000, and a 64-1000T, which is the Tatum A-Arm version (front steer). That's where I got that idea.
64-1000: http://sacoperformance.com/proddetail.php?prod=64-1000
64-1000T: http://sacoperformance.com/proddetail.php?prod=64-1000T
By the way, one thing that really confused me is the design of the tie-rod mount of the so-called "beam type" steering racks: nearly all of them have an asymmetric bracket, with an extended tab at the bottom for a power-steering or damper attachment. That feature is lacking on most of the so-called "front-steer" designs, which threw me. Go figure. |
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JWHracing
Samba Member
Joined: September 17, 2008
Posts: 234
Location: Mesa, AZ
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| Posted: Mon Sep 17, 2018 4:47 pm Post subject: Re: Rack-and-Pinions: A-Arm or VW Beam-Type? |
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The difference between a beam rack and an a-arm rack is typically the spacing between the tie rod holes. The different spacing is what minimizes bump steer in the appropriate set ups. Beam cars benefit from running the longest tie rod possible, which in this case makes the mounting holes for the tie rods on the rack right next to each other.
A-arm racks will have a wider spacing, or will mount to the end of the rack (referred to as an end-load rack and pinion).
The Tatum style rack is made and mounted like a beam style rack, but has a wider spacing that better matches the pivot of the a-arms on Tatum built cars.
If you are running a beam, you need a beam style rack. Anything else will cause bump steer and will handle poorly.
1.5 to 1 ratio is what you need.
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65 Baja - Class 5 Unlimited Race Car
2021 STORR Pro Air Cooled Buggy Champion
2019 AZOP Unlimited Buggy Champion
2017 SADR 1300 Class Champion
2016 AZOP Limited Buggy Champion
Currently "retired" from racing
Last edited by JWHracing on Mon Sep 17, 2018 5:34 pm; edited 1 time in total |
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Busstom
Samba Member
Joined: November 23, 2014
Posts: 3841
Location: San Jose, CA
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| Posted: Mon Sep 17, 2018 5:24 pm Post subject: Re: Rack-and-Pinions: A-Arm or VW Beam-Type? |
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Ouch. Did'ja have to go 'n say that?
Do you think it will really be an issue on a lowered Bus, which will have pretty minimal travel anyway? (Relatively speaking.)
I s'pose I can call Saco and see if they sell just the rack, and drop it in my box. 
You do point out the most obvious difference in beam vs. A-arm racks. |
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JWHracing
Samba Member
Joined: September 17, 2008
Posts: 234
Location: Mesa, AZ
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| Posted: Mon Sep 17, 2018 5:33 pm Post subject: Re: Rack-and-Pinions: A-Arm or VW Beam-Type? |
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You should be able to get a replacement rack slide no problem.
I don't know if the amount of fabrication needed to install a rack is worth the effort. There's plenty of slammed buses around with stock style steering. I know you already have the rack, but if you have to buy different parts to make it work, is it worth it? Keep in mind you will need appropriate steering joints to connect the steering bus steering column and shaft to the rack, the mount to mount the rack to the beam and the appropriate fabrication to make it right, etc etc.
Rack and pinion setup takes time to do it right. Although it is "universal" it takes a lot of measuring to install the rack at the correct angle that minimizes bump steer.
_________________
65 Baja - Class 5 Unlimited Race Car
2021 STORR Pro Air Cooled Buggy Champion
2019 AZOP Unlimited Buggy Champion
2017 SADR 1300 Class Champion
2016 AZOP Limited Buggy Champion
Currently "retired" from racing |
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JWHracing
Samba Member
Joined: September 17, 2008
Posts: 234
Location: Mesa, AZ
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| Posted: Mon Sep 17, 2018 5:38 pm Post subject: Re: Rack-and-Pinions: A-Arm or VW Beam-Type? |
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Also, for your knowledge, front vs. rear steer on a rack is determined by the tie rod placement on the spindles. Every beam style suspension has the tie rod mounted off the back of the spindle. Some a-arm setups have the mounting for the tie rod located off the front of the spindle, towards the front bumper. When you build something with a-arms, the spindle determines whether you would need a front steer rack or a rear steer rack. Both setups have their pros and cons, but the biggest determination is how the builder fabricates the spindles, and how much room is available in the chassis and the style of chassis.
_________________
65 Baja - Class 5 Unlimited Race Car
2021 STORR Pro Air Cooled Buggy Champion
2019 AZOP Unlimited Buggy Champion
2017 SADR 1300 Class Champion
2016 AZOP Limited Buggy Champion
Currently "retired" from racing |
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Busstom
Samba Member
Joined: November 23, 2014
Posts: 3841
Location: San Jose, CA
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| Posted: Mon Sep 17, 2018 5:39 pm Post subject: Re: Rack-and-Pinions: A-Arm or VW Beam-Type? |
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| JWHracing wrote: |
You should be able to get a replacement rack slide no problem.
I don't know if the amount of fabrication needed to install a rack is worth the effort. There's plenty of slammed buses around with stock style steering. I know you already have the rack, but if you have to buy different parts to make it work, is it worth it? Keep in mind you will need appropriate steering joints to connect the steering bus steering column and shaft to the rack, the mount to mount the rack to the beam and the appropriate fabrication to make it right, etc etc.
Rack and pinion setup takes time to do it right. Although it is "universal" it takes a lot of measuring to install the rack at the correct angle that minimizes bump steer. |
You hit the nail on the head. All the fab is done, and there's no going back. Long-gone is the Bus steering box, and the CNC dual-master brake reservoirs sit partially where the stock steering box used to reside. And it had to be that way...once I chopped the Bus, the new seating posture was laid back, not unlike a Maserati. So to tilt the stock steering column that far back meant that I could no longer enter or exit the vehicle, it was essentially lying on the wheel well. So rack it is.
Last edited by Busstom on Mon Sep 17, 2018 5:44 pm; edited 1 time in total |
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Busstom
Samba Member
Joined: November 23, 2014
Posts: 3841
Location: San Jose, CA
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| Posted: Mon Sep 17, 2018 5:43 pm Post subject: Re: Rack-and-Pinions: A-Arm or VW Beam-Type? |
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| JWHracing wrote: |
| Also, for your knowledge, front vs. rear steer on a rack is determined by the tie rod placement on the spindles. Every beam style suspension has the tie rod mounted off the back of the spindle. Some a-arm setups have the mounting for the tie rod located off the front of the spindle, towards the front bumper. When you build something with a-arms, the spindle determines whether you would need a front steer rack or a rear steer rack. Both setups have their pros and cons, but the biggest determination is how the builder fabricates the spindles, and how much room is available in the chassis and the style of chassis. |
Thanks for that, too. That was pretty much my mentality going into this. So to restate, narrowed Bay beam with rear-actuated spindles, only glitch at this point would seem to be the roughly 5-inch spread on the tie-rod mountings vs. about 2 inches on a beam-style R&P. |
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JWHracing
Samba Member
Joined: September 17, 2008
Posts: 234
Location: Mesa, AZ
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| Posted: Tue Sep 18, 2018 7:28 am Post subject: Re: Rack-and-Pinions: A-Arm or VW Beam-Type? |
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The rack you have will probably be fine. It just means really short tie-rods. Without seeing your setup I don't know if you will have interference with the pan head or not. I really don't know what a bus has as far as beam mounting.
On my baja, to get the steering right to the point that it only has a 1/2" of toe change through 12" of travel, I had to cut the frame head off leaving only about 3" of the lower part of the frame head. This isn't a problem on my car because it has a full cage through out, so strength isn't a concern. I don't know if that will create problems in your build.
_________________
65 Baja - Class 5 Unlimited Race Car
2021 STORR Pro Air Cooled Buggy Champion
2019 AZOP Unlimited Buggy Champion
2017 SADR 1300 Class Champion
2016 AZOP Limited Buggy Champion
Currently "retired" from racing |
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Busstom
Samba Member
Joined: November 23, 2014
Posts: 3841
Location: San Jose, CA
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| Posted: Wed Sep 19, 2018 7:02 am Post subject: Re: Rack-and-Pinions: A-Arm or VW Beam-Type? |
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| JWHracing wrote: |
| The rack you have will probably be fine. |
That is my hope (sad that I can only hope, huh?  ) Actually, I wouldn't mind taking it to a race shop or something and have it checked after build. Or rig a measurement system, or....
| JWHracing wrote: |
| It just means really short tie-rods. |
Yes, right now, they'll be roughly 20 - 22 inches or so, eyeballing it. The rack is behind the beam and really low, almost on plane with the spindle steering arms.
Thanks for your input! |
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