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Rear steer.....and go

JR4X said:
The right stuff isn’t in his corner of the country
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There are places in his area that I can think of. Problem is he goes to those places and does 90mph missing all the good slow crawling stuff that's not boring and ends up breaking his junk doing bouncer things before he sees the good stuff. :lmao:

Bebop :flipoff2:
 
'84 Bronco II said:
So same as the $2,000 RDT pump? Even with the losses, seems like for $700, it could be a good fit for a crawler application that needs maximum speed near idle and rarely hits 6,000 RPM. I want to say I've seen Eric post that the RDT is good for 8,000-9,000 RPM though? I am sure the RDT is a superior product, but for $700 vs. $2,000, is it really worth it for a recreational application? I was doing some math the other day, and it takes a shit ton of volume to have reasonably fast steering with a 3" ram.
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The Scott's pump is a Dynamic brand gear pump paired with his own bearing block and the pump itself is .85 c.i./rev or 13cc displacement so it's not much larger than our Pro Series TC which is 11cc. Our RDT is 20cc by comparison.

Volumetric efficiency is the big difference where gear pumps suffer, especially at low rpm. Because they work by trapping oil in between the teeth of a gear and the wall of the pump housing, there is always a clearance gap resulting in internal leakage from cavity to cavity. At low rpm and high pressure, the efficiency of these pumps (actual flow rate versus theoretical flow rate) can drop as low as 70%. With a sliding vane type pump like the TC and RDT, volumetric efficiency will be closer to 90-95% at the same conditions so despite having slightly smaller displacement, customers that have swapped over to our Pro Series TC have consistently reported better steering feel at low rpm and across the board.

The numbers that commonly circulate for the Scotts pump of 20 GPM are the theoretical flow for a 13cc displacement pump at 5500 RPM although in reality, with any non-flow controlled pump including vane pumps (i.e. billet TT pumps and PSC "race" CBR pumps), you will reach a max flow rate where the pump just can't pull any more fluid in from the reservoir and begins to cavitate. This is entirely dependent on the size of the feed hose, reservoir design, and tank pressure but with a -12 feed, I can tell you a Scotts pump won't put out more than 12 GPM and with a -16 feed hose will be around 15 GPM max.

Once you reach around 6 GPM (our standard Pro TC), you are able to keep up with most any orbital used for crawling and with rear steer, you aren't exactly able to utilize double the flow so pushing more through the system provides no real extra benefit other than rear steer quickness. For people that need a little extra, we don't advertise it but we do make our TC pumps up to an 8 GPM output limit. I just like to go through the complete system with people before offering it because the rest of the system becomes that much more critical at the higher rate.

As for RPM, I have no problems sending our Pro Series TC up to 8K RPM or even a little higher for short durations. I try to keep the RDT limited to 7500 and have several trophy trucks running up in the 6-7K rpm range for extended periods with no concerning wear. Other pumps like our Trail Series TC or a gear pump, I would try to keep down around 6000 to 6500 max if possible.

Over the past two years since launching the Pro Series TC, we have built and sold hundreds of them, many for single pump front and rear steer buggies and there have been very few drivers that felt like they needed any more power than this pump could provide.
 
RadialDynamics said:
Over the past two years since launching the Pro Series TC, we have built and sold hundreds of them, many for single pump front and rear steer buggies and there have been very few drivers that felt like they needed any more power than this pump could provide.
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Do you mean in the standard 6 gpm Pro TC or the "more customized" Pro TC 8 gpm?
 
RadialDynamics said:
6 GPM is by far our most popular. We have only made a handful of 8 GPM options and those are mainly for guys that are racing with a larger orbital and don't have the budget for the RDT.
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I’ve been trying to tell people since 2015 that 6 gpm is the high side of what you can realistically use.

Every CC above that is wasted horsepower and heat soak.
 
RadialDynamics said:
6 GPM is by far our most popular. We have only made a handful of 8 GPM options and those are mainly for guys that are racing with a larger orbital and don't have the budget for the RDT.
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Thanks....got plans for a pair of 4WS portal cars with 3x9" DE cylinders and was wondering if I needed to order up the 8 gpm pump...but sounds like the 6 is fine.

Appreciate your knowledge and input here!
 
My main issue with the TC and big orbital was very specific.

When you enter a sharp corner at a decent rate of speed and flick the car, when the back end start to rotate, it takes a fair bit of volume to achieve a nice counter steering. This usually happens when hard on the brakes (hydroboost), with the engine at lower RPM (no gas, foot on the brakes) and the TC pump at this RPM range wasn't providing enough volume to keep everything happy.

I've got a couple of buddies racing U4 and they're super happy with the RD Pro-TCs in the 6GPM flavor.
 
JR4X said:
If you think you need that much pump you are better off doing the Scott’s Offroad gear pump. It’s one pump for the price of two but it’s 5 times the pump. If I ever get around to building my rear steer buggy it’s the pump I plan to use.
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If that’s the new monster truck pump or whatever a guy we wheel with just bought cutlers blue and silver buggy and that pump is doing all kinds of weird stuff. Clicking and spewing fluid out randomly
 
Cracksrubi said:
If that’s the new monster truck pump or whatever a guy we wheel with just bought cutlers blue and silver buggy and that pump is doing all kinds of weird stuff. Clicking and spewing fluid out randomly
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That sounds right. They are noisy from what I understand.
 
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