HP to Weight Ratio and Ural Top Speed

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HP to Weight Ratio and Ural Top Speed

Post by JackReno » Sun Aug 25, 2019 10:41 pm

I was wondering as a person that does not own a Ural yet why does Ural say for 2019 that the average top speed is 65 to 75 mph and has 41 hp and weights 730 lbs with a 4 speed and a modern fuel inject system..
But if you look at the specs of a old 1938 Ford sedan with a V-8 with 85 hp, 2 barrel carb, 3 speed that weights 2800 lbs or more and some say it can cruise 85 to 100 mph if needed and top out at 110 mph with 2 people on board..

So how can something that heavy with far more wind drag go so much faster and only have twice the HP and HP to weight ratio is worse than the Ural..

Just thinking

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Re: HP to Weight Ratio and Ural Top Speed

Post by JackReno » Sun Aug 25, 2019 11:14 pm

So to put this into perspective from my post above :

1938 Ford sedan with 85 hp to 2800 lbs has a ratio of 1 hp to 38.9 lbs.

2019 Ural gear up has 41 hp to 730 lbs has a ratio of 1 hp to 17.8 lbs

So why is the Ural slower, is the gearing that low..

Note I am not looking for a high speed bike when buying a Ural but was wondering why it is slower to begin with when it can be so much better..

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Re: HP to Weight Ratio and Ural Top Speed

Post by windmill » Sun Aug 25, 2019 11:35 pm

Because it's far more complicated than power to weight ratio since its a matter of rolling resistance and aerodynamics, not dead lifting weight.
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Re: HP to Weight Ratio and Ural Top Speed

Post by JackReno » Sun Aug 25, 2019 11:54 pm

I am curious what is the rpm's at 65 mph on a 2019 gear up, I heard its around 4500 rpm's, is that right..

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Re: HP to Weight Ratio and Ural Top Speed

Post by atlasheating » Mon Aug 26, 2019 9:02 am

I think the main thing to consider is Torque. An old VW engine produces 40 HP but has about 80Ft Pounds of Torque.
I don't know the torque of the old Ford Flathead Engines.
My chart for older Urals shows 65MPH at 4650RPM

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Re: HP to Weight Ratio and Ural Top Speed

Post by INSUBORDINATOR » Mon Aug 26, 2019 9:39 am

Most of us with older Urals, still have them because they don't run them anywhere near "top Speed" for long periods. If I wanted an interstate highway rig - I Might use a Ural sidecar on an older GOLD WING. It would be a much BETTER TOOL for that Job.
No experience with the new F.I . Models, & no data on how the hold up at highway speeds. Even though they have improved gears - the heads valves & cranks are still Ural - so I wouldn't push them to the max, especially @ their current prices. Getting warrantee repairs from anyone is not easy or fun - especially with a small dealer network. You may be asking for more than it was designed to do.
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Re: HP to Weight Ratio and Ural Top Speed

Post by RC20 » Mon Aug 26, 2019 2:07 pm

JackReno wrote:
Sun Aug 25, 2019 11:54 pm
I am curious what is the rpm's at 65 mph on a 2019 gear up, I heard its around 4500 rpm's, is that right..
I have two posts on that subject, one in the Virtual watering hole and one in the 2014 and Newer Wrenches

While not spot on, you will be right at 4650 at 65 mph (that is a 50 rpm error).
2011 Ural GU Speed RPM.JPG
To answer your question, its not a hp limit, its is what an the engine can take limit.

5300 RPM continuous would be the menstruation (and a break every two hours).

Hp and more important torque is there to acceleration, pass, maneuver if needed.

My calcs show that at 85 you are on the red line of the Ural. Note that is a short period red line, you are in what would be called yellow just below that , don not stay there very long. Heidla at a Ural up to 83 and it was still going.
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Re: HP to Weight Ratio and Ural Top Speed

Post by RC20 » Mon Aug 26, 2019 2:13 pm

The heads valves & cranks are still Ural
While I fully agree on don't push it, the head is new. Crank and valves are the newer editions

Note that the head is larger withe more cooling and the piston now has a band on it (that reduces or stops piston slap on a longer stroke engine)

I have worked with those bands on oiless air compressors, I have never worked on an engine that has them so long term it will be interesting.

You alwyas hope a changed does not affects something else (shouldn't but the world is full of surprises)

So far all the updgrades look to have been well thought out and tested.

I don't think we have good current data on performance, but going with the older data is safe and 75 looks to be as fast as I want to go on one and not often if I can help it. I an a bit of freeway Washington State and just stayed in the truck lane which was 60 and was perkily happy there.

AK max speed is 65 and I am running that but its not continuous, you hit hills and curves and it slows you down.
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1 x R80GS (ok to start with, learned to love it for what it was)
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Re: HP to Weight Ratio and Ural Top Speed

Post by Msblu79 » Mon Aug 26, 2019 2:17 pm

It might be built in 2019 but it was not designed in 2019. The basic format and design of this rig is from 1934/38 timeframe and is still very much from that era. Urals are not everyones cup of tea, not fast, daily maintenance required, reliability issues. Consider carefully your real needs and your abilities to keep it running without dealer support. Insubordinator said it above, "get the right tool for the job". Ural's have their limitations and one must be realistic about it filling your riding needs. :)
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Re: HP to Weight Ratio and Ural Top Speed

Post by RC20 » Mon Aug 26, 2019 4:01 pm

It might be built in 2019 but it was not designed in 2019. The basic format and design of this rig is from 1934/38 time frame and is still very much from that era.
I think the era it came form is relevant.

While the frame and layout may be roughly the same everything that goes on it has been upgraded.

The engine has no resemblance to the original. Its an all new engine from the original Flathead and is been improved again 2014.

The limiting factors are the engine (primarily ), gearing, Ural's weight (and a side car design no matter how modern is going to have limits with handling no matter what)

Loose 100 lbs and the engine is not working as hard at an given RPM and you could go faster with the current (connecting rod speed and forces and crank ability to take RPM has to be factored in)

That said, if you want to run 85+ through corners and hills then the modern 2 wheelers suit that to a T.

They just can't do what the Ural does.
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Formerly Owned: ( various rides on others)
Honda 90
2 x CB750K (one a true Japan Model flown to Hawaii by a P3 Orion Sub Patrol Aircraft!)
1 x CB700 SC ala Shaft Drive Nighthawk S (RC20 is the actual in house production Model)
1 x R80GS (ok to start with, learned to love it for what it was)
1 x CB450K

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Re: HP to Weight Ratio and Ural Top Speed

Post by windmill » Mon Aug 26, 2019 4:23 pm

The basic layout of the 750 engine hasn't changed much, but the quality of the components has changed dramatically.

The length of it's stroke and being a 2 valve pushrod configuration ultimately sets it's limits. The improvement of the components raised the levels that can be sustained within those limits.

Mechanically the 2018's and 2019's are virtually identical, and IMWA recommends the same parameters for their use. The 2019's do produce more useable power because of its superior fuel management. The changes in the heads and oil system address emissions issues, not mechanical, or running temps. The new sump is to stabilize temps, not decrease them, the fuel system does that.
Last edited by windmill on Mon Aug 26, 2019 4:56 pm, edited 1 time in total.
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Re: HP to Weight Ratio and Ural Top Speed

Post by JackReno » Mon Aug 26, 2019 4:29 pm

Maybe the Ural does need a 5 speed so the rpm's can drop to cruise at 65 to 75 with less wear on the motor..

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Re: HP to Weight Ratio and Ural Top Speed

Post by windmill » Mon Aug 26, 2019 5:01 pm

JackReno wrote:
Mon Aug 26, 2019 4:29 pm
Maybe the Ural does need a 5 speed so the rpm's can drop to cruise at 65 to 75 with less wear on the motor..
It's mostly not a gearing issue, it's the limits of its low HP and torque to push a highly aerodynamically challenged object through the air.
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Re: HP to Weight Ratio and Ural Top Speed

Post by RC20 » Mon Aug 26, 2019 5:56 pm

Windmill hits a key aspect right on the head (well in this case the Nose!)

Ural is much like an aircraft, you have that wind resistance that is a limiting factor short of more HP (toque). I would like to see new torque and hp curves but its close enough. My R80GS was listed as max 70 mph though it could easily do more than that. Inherent in the limitation of the engine.


Looking a the cart you can see the hp and torque are both falling off rapidly after 5500. So, a realistic weight for a fairly bare bones Ural is 1000 pounds. Dry weight is 730 for your GU, but it has a tire added, tools, rider at lets call it 200 lbs average with gear, a few odds and ends in the tub and 1000 is more than reasonable. So its moving over 1000 lbs and a lot of wind resistance. 75 and the engine is being worked really hard.

If you read WWII specs, engines had a thing called WEP (War Emergency Power). You could run that for 5 minutes, any more and the engine was an immediate requirement for overhaul (assuming you made it back as it could flat break on you at andy point over 5 minutes), granted if I was getting shot down I would risk it but those are sharp limits)

The Ural has a 6200 RPM red line , but that is a pulse red line, you don't want to go there unless its an emerny6 (someone coming up fast on your butt and you need to get up to speed).

Ural has to figure out where to put its development money. Its not unlimited and it had serious needs in the engine, trany and FD (not to mention the Emissions which have to be a bugger). For the rare individual that wants to go 90 mph or faster, then they will simply point you to a BMW etc and

https://www.dmcsidecars.com/products/
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Formerly Owned: ( various rides on others)
Honda 90
2 x CB750K (one a true Japan Model flown to Hawaii by a P3 Orion Sub Patrol Aircraft!)
1 x CB700 SC ala Shaft Drive Nighthawk S (RC20 is the actual in house production Model)
1 x R80GS (ok to start with, learned to love it for what it was)
1 x CB450K

Current:
1 x 2019 cT Terracotta

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Re: HP to Weight Ratio and Ural Top Speed

Post by Mr Wazzock » Fri Aug 30, 2019 7:33 am

So how can something that heavy with far more wind drag go so much faster and only have twice the HP
You gave the answer in the second paragraph, "V8", so the answer is, lots of cubes. So it's not all because of horsepower. :D
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