Heng Long MERKAVA review, build out and field testing.

[huckOhio]

Don't try to overthink the installation and make it harder on yourself. It really is as simple as I just said.

Thank you for the advice. I've been emailing Rich and he helped me figure it out using the BB tube.

Thanks again!

[Rubicon99]

Rich, I tried that and here is what I found (forgive me, I am not mechanically inclined).

Both ends of the BB tube are different sides. The end that is inside the airsoft gun is 8.4mm (OD) and the end that slides in the tank barrel is 7.3mm (OD). The BB tube fits into the barrel with .6mm slop. The barrel is moved by a metal bracket that connects the barrel to a slide on the airsoft mechanism. There is not real "connection" between the BB metal tube and the barrel.

The barrel ID is 7.9mm
The ID of the recoil unit carriage is 8.4mm.

Only one end of the BB tube can slide in the tank barrel with approximately 6mm slop. The other end of the BB tube cannot fit into the barrel opening.

Both ends of the BB tube slide freely in the recoil carriage. I really don't see how this setup will work since it appears to depend on a compression fit between the barrel and tube & tube and recoil unit.

Here is a pic of the BB tube.



I really appreciate any suggestions/help to get this to work.

Thanks
Mike

I have installed four of the Mod 1B recoils into Merkavas and at least a dozen into other HL and TD tanks without any issues. All of them work great.

For the Merkava all you need to do is re-install the stock HL extension tube into the stock HL barrel as it came out of the tank. The extension should have been attached to the stock barrel with a set screw. The fact that the two HL parts are loose it not the fault of the Mod 1B recoil unit.

The HL extension tube used on the Merkava is loose in the Mod 1B recoil unit because the tube is designed to be held in place with a tight fitting rubber "O ring" seal in the stock HL BB unit. The extension is slightly smaller in diameter then the usual "machined in" extension normally present on HL barrels. A such you will need to "mimic" the "O ring" by simply adding a thin tape (such as electrical tape) around the part of the extension that goes into the recoil.

Don't try to overthink the installation and make it harder on yourself. It really is as simple as I just said.

[huckOhio]

Mike, you use the bb tube that is stuck inside the airsoft gun. It is held in by an O ring and feels tight but just give it a yank and it will pull free. Then you attach that back to the breech of the main gun and stick the tube into the recoil shuttle.

Rich, I tried that and here is what I found (forgive me, I am not mechanically inclined).

Both ends of the BB tube are different sides. The end that is inside the airsoft gun is 8.4mm (OD) and the end that slides in the tank barrel is 7.3mm (OD). The BB tube fits into the barrel with .6mm slop. The barrel is moved by a metal bracket that connects the barrel to a slide on the airsoft mechanism. There is not real "connection" between the BB metal tube and the barrel.

The barrel ID is 7.9mm
The ID of the recoil unit carriage is 8.4mm.

Only one end of the BB tube can slide in the tank barrel with approximately 6mm slop. The other end of the BB tube cannot fit into the barrel opening.

Both ends of the BB tube slide freely in the recoil carriage. I really don't see how this setup will work since it appears to depend on a compression fit between the barrel and tube & tube and recoil unit.

Here is a pic of the BB tube.



I really appreciate any suggestions/help to get this to work.

Thanks
Mike

[RichJohnson]

I received the HL Merkava RC tank for xmas. This is my first RC tank, and based your posts I purchased the parts to upgrade the turret ring, motors, controller to 7.1, and the recoil unit. I purchased the same recoil unit and started working on installing yesterday, but saw that there is no way to connect the barrel to the recoil. Could you please LMK how you did this? Pics would be helpful (if available).

Thanks!
Mike

Mike, you use the bb tube that is stuck inside the airsoft gun. It is held in by an O ring and feels tight but just give it a yank and it will pull free. Then you attach that back to the breech of the main gun and stick the tube into the recoil shuttle.

[huckOhio]

PART 3: Turret mechanical rework has begun.

Since I am upgrading the Merkava to a 7.1 system I decided to ad in a servo recoil system. I am using a JVM3Dconcepts servo recoil system (available through RichJohnson who can be reached via a PM on this site) but will be maintaining the HL stock elevation system for now.

I received the HL Merkava RC tank for xmas. This is my first RC tank, and based your posts I purchased the parts to upgrade the turret ring, motors, controller to 7.1, and the recoil unit. I purchased the same recoil unit and started working on installing yesterday, but saw that there is no way to connect the barrel to the recoil. Could you please LMK how you did this? Pics would be helpful (if available).

Thanks!
Mike

[cmdrcody]

The two files I have from '3D Cult' are for the 1/16 scale Merkava MK IV. Rich, I'll send you a private message.

[RichJohnson]

I have seen them in 1:35 scale. I don’t know how to manipulate the file to blow it up to make it fit. Do you have it already in 1:16 scale?
I can print it if you do. IDE like one as well. Making it fit the tank is a different issue with the post locations

[cmdrcody]

Can anyone 3D print a "cope cage" for the Merkava MK IV for me?
I have two '.stl' files available with different configurations of the cage.

[cmdrcody]

Okay, I've got it done to the point where it's ready to put in the field. There was one appendant part missing and I also want to install the optional machine gun w/flash in place of the non-functional machine gun above the barrel. Contacted Toucan about the missing part and getting the flashing machine gun. They replied back very quickly and those parts are on the way to me. Great customer service from Toucan!

[cmdrcody]

It arrived yesterday and I unboxed it this morning. WOW!, This has the largest turret I've seen in all the HL 1/16 RC tanks. Be aware that the instructions don't show the little latch you need to move to remove the battery hatch (In photo painted red). The turret motor/gear assembly is the smoothest of all the HL tanks. It doesn't make a bunch of clicking noises like the other do by the gear skipping on the turret gear ring. Which is nice because the turret needs to be moved to a 90 degree location to access both the power switch under the driver's hatch and to remove the battery cover. Will start today to install the add-on parts.

[RichJohnson]

As I said it’s quite easy to install your own servo on my recoil unit without buying one that uses the cog gears to elevate.

I usually do the servo elevation conversion with a larger hitec servo so it has more power for elevating and supporting the barrel against bouncing while driving, though my newer 3d barrels are much lighter than the turned aluminum ones I first marketed and the early resin mould cast ones I made.
I put a screw with a flat head and a small tube around it as support and screw it to the last post on the servo arm and then eyeball the placing of the servo in the turret so the servo arm gives the maximum amount of movement of the barrel with the screw post in th track on the side of the elevation unit.
I have also added a tiny 2mm ball bearing on the end of the arm in the channel ( I supply those tiny ball bearings in my Sherman hvss kit for the return rollers)
Diong this I can create maximum elevation and depression which is optimum for IR battling a tank.

You can see this kind of install in my Tamiya leopard 1 with an older Clark recoil unit below.

[keilau]

I have watched Merkava tanks fire and repair fire without elevating so I say no auto loader.

what’s the best recoil? Mine because you don’t have to sand or prep it and cost wise it’s cheaper.

all other 3d recoils have to be sanded a lot and they cost more.
metal recoils cost about 100 bucks in average.
some offers cog and gear for the servo to add elevation but I have found with them you get very little rage of motion available where as making a longer arm for the henglong elevation unit and connecting it to mine or using a servo with a pin in the channel on the side of my recoil unit you can get full range of motion that the barrel will move up and down but you do have to be a bit ingenious to rig this up, some experience with rc in the past helps.

Of course, I'm biased with my opinion but I base it mostly on experience, not because I want every tank yo have my flawless recoil unit in them.

Now everyone does have what they like to use, and others may like those more expensive models with more frills that don’t work out so well but that’s up to you.

RichJohnson, you always gave unbiased, honest opinion and I benefit from them. You have the best servo recoil for the Merkava. It should be the best servo barrel recoil for the US Army Abrams too, which also does not auto load. The US Army believe manual shell loading is faster and more trouble free. Your barrel recoil should be ideal for older MBT such as the M60 and UK Centurion.

The Leopard does need a combined servo recoil. The Heng Long metal servo recoil is quite cheap from the Toucan US Store (< $50), but, as you said, it needs a lot of gridding to fit it to the tank.

[RichJohnson]

Let me know if you want a servo recoil unit for your merkava.
Remember you need to upgrade the controls to a 7.1 system so if you plan a recoil you should order your system now to have it for your build out.

Also look into using model Rail Road chain instead of the Henglong supplied chain, theirs is way too big. Large O scale chain should work well.

I have watched Merkava tanks fire and repeat fire without elevating so I say no auto loader.


what’s the best recoil? Mine because you don’t have to sand or prep it and cost wise it’s cheaper.

all other 3d recoils have to be sanded a lot and they cost more.
metal recoils cost about 100 bucks in average.
some offers cog and gear for the servo to add elevation but I have found with them you get very little rage of motion available where as making a longer arm for the henglong elevation unit and connecting it to mine or using a servo with a pin in the channel on the side of my recoil unit you can get full range of motion that the barrel will move up and down but you do have to be a bit ingenious to rig this up, some experience with rc in the past helps.

Ofcourse, Im biased with my opinion but I base it mostly on experience, not because I want every tank yo have my flawless recoil unit in them.

Now everyone does have what they like to use, and others may like those more expensive models with more frills that don’t work out so well but that’s up to you.

[keilau]

Let me know if you want a servo recoil unit for your merkava.
Remember you need to upgrade the controls to a 7.1 system so if you plan a recoil you should order your system now to have it for your build out.

Also look into using model Rail Road chain instead of the Henglong supplied chain, theirs is way too big. Large O scale chain should work well.

Does the IDF Merkava IV have auto loading? If it does, the gun tilts up for reload after the recoil. The HL built-in recoil does not support that.

What is the best combined servo recoil and elevation unit available?

[RichJohnson]

Let me know if you want a servo recoil unit for your merkava.
Remember you need to upgrade the controls to a 7.1 system so if you plan a recoil you should order your system now to have it for your build out.

Also look into using model Rail Road chain instead of the Henglong supplied chain, theirs is way too big. Large O scale chain should work well.

[cmdrcody]

Well, I just dropped the dime on the Panzer DF Merkava MK IV (TH22646-CX-DZN1) from the Toucan US warehouse. It has all metal parts with the exception of the road wheels. It really beat the pricing, even with adding in the shipping cost, with all the options this came with from our other HL US distributors.
And Toucan Hobby was kind enough to give me a discount code since I've purchased from them in the past. Thank you Toucan!
I'll post some photos once it arrives and through the build process.
I'll also be watching closely of the members on this thread going through the process of upgrading their Merkava RC tanks

[keilau]

I'm one of those folks that adds magnets to get into my tanks easier for maintenance which is why I add stiffeners or pour resin in the lower hull. I agree that if I didn't mod my tanks, those steps wouldn't be necessary.

For me, what a hull shaft bearing designed for is to stop side loading of the bearings in the gearbox connected to the shaft. When I say side loading I mean the weight of the tracks and sprocket pulling down and back (for front sprocket tanks) due to the track tension. For light tanks with plastic tracks...no need for the bearings. Heavy tanks with heavy tracks could benefit from the additional bearings, but while they improve gearbox stability they also put additional drag on the motors. It's not that much drag on the motors if the gearboxes and hull bearings are properly aligned. Using a hull bearing to remove a wobbly shaft is a bad idea IMO. The shaft is wobbly because the bearings in the gearbox are either bad from being side loaded, the shaft is bent, or the gearbox metal in the shaft area is bent. Adding a bearing to the hull to correct that problem is a bad idea that will only cause additional stress on the motors as you are trying to make a bearing straighten out the wobble. The shaft wobble should be fixed before a hull bearing is added. That will help prevent the wobble from coming back.

I totally agree with you that a user cannot use a bearing to correct the wobbling of a bent drive axle. I use Heng Xin and Torro ball bearings gearbox on my tanks. They both use strong, high quality axle on their gearbox. I have disassembled the Heng Xin gearboxs and re-lubricate them and have not found any bent or misaligned drive shaft yet. If the user find a bent axle, the gearbox must be thrown out and replaced. The best solution is to spend the extra money on high quality gearboxes.

I was always super careful about the alignment of the gearbox at a perfect 90 degrees between the tank axle and the drive axle. If the user sees a visible wobbling of the drive axle, the gearbox is severely mis-installed. I believed I did a good job installing the Heng Xin gearbox on the Leopard 2A6 until I got the Heng Long metal drive axle bearing kit. I found that the right drive axle is perfectly aligned, but I have to loosen the left gearbox to realign the drive axle. I estimated the misalignment is about half a degree and too small to see any wobbling. The realignment significantly reduced the noise and vibration or the Leopard. It does a much better job than eyeballing the gearbox alignment. I am very happy with the $12 investment.

Heng Long uses high quality plastic and thick chassis walls to give the chassis plenty of strength. But the plastic is an inherently flex material. I like you idea of adding metal braces to the chassis, but it is beyond the ability of most tankers. The axle drive bearing kit from HL is a cheap and effective improvement for the aft chassis.

Flex structure is NOT always bad. Next time when you fly a Boeing 787, look out the window and you can see its wings bent up as if it is going to break. Don't worry. It is called the flexible wing, a feature of most modern aircrafts. We used to design the aircraft wing as rigid as possible to assure predictable aero characteristics. With modern avionics, the flexible wings have lighter weight, better controllability and safety. (Sorry about the off topic story on structure flexibility.)

[Rubicon99]

I'm one of those folks that adds magnets to get into my tanks easier for maintenance which is why I add stiffeners or pour resin in the lower hull. I agree that if I didn't mod my tanks, those steps wouldn't be necessary.

For me, what a hull shaft bearing designed for is to stop side loading of the bearings in the gearbox connected to the shaft. When I say side loading I mean the weight of the tracks and sprocket pulling down and back (for front sprocket tanks) due to the track tension. For light tanks with plastic tracks...no need for the bearings. Heavy tanks with heavy tracks could benefit from the additional bearings, but while they improve gearbox stability they also put additional drag on the motors. It's not that much drag on the motors if the gearboxes and hull bearings are properly aligned. Using a hull bearing to remove a wobbly shaft is a bad idea IMO. The shaft is wobbly because the bearings in the gearbox are either bad from being side loaded, the shaft is bent, or the gearbox metal in the shaft area is bent. Adding a bearing to the hull to correct that problem is a bad idea that will only cause additional stress on the motors as you are trying to make a bearing straighten out the wobble. The shaft wobble should be fixed before a hull bearing is added. That will help prevent the wobble from coming back.

Yes you are correct the proper term is preload. I used "wobble" to paint a visual picture for those new to tanks. The preload often gives the sprockets a look as though they are wobbling.

YES using the bearings to fix a bent axle issue is absolutely not a good idea and should not be used to do so.

[tank_me]

I'm one of those folks that adds magnets to get into my tanks easier for maintenance which is why I add stiffeners or pour resin in the lower hull. I agree that if I didn't mod my tanks, those steps wouldn't be necessary.

For me, what a hull shaft bearing designed for is to stop side loading of the bearings in the gearbox connected to the shaft. When I say side loading I mean the weight of the tracks and sprocket pulling down and back (for front sprocket tanks) due to the track tension. For light tanks with plastic tracks...no need for the bearings. Heavy tanks with heavy tracks could benefit from the additional bearings, but while they improve gearbox stability they also put additional drag on the motors. It's not that much drag on the motors if the gearboxes and hull bearings are properly aligned. Using a hull bearing to remove a wobbly shaft is a bad idea IMO. The shaft is wobbly because the bearings in the gearbox are either bad from being side loaded, the shaft is bent, or the gearbox metal in the shaft area is bent. Adding a bearing to the hull to correct that problem is a bad idea that will only cause additional stress on the motors as you are trying to make a bearing straighten out the wobble. The shaft wobble should be fixed before a hull bearing is added. That will help prevent the wobble from coming back.

[Rubicon99]

For us to understand the effectiveness of the HL metal axle bearing, we must know its design purpose. Since I have no connection with the Heng Long design team and unlikely to receive any confirmation from them, the opinion is a personal one based on my experience as an aeronautical engineer. (You can Google "Kei Yun Lau Boeing" if you are interested in my background.)

First, the bearing for the drive axle is NOT for friction reduction. An open air hole through the plastic chassis is the lowest friction design. Old time HL tanker will notice that the RC tank runs with lots of noise and vibration. The Heng Long Metal Driving Axle Bearings do three things to reduce the noise and vibration.

1. The metal housing makes the chassis more rigid around the gearbox.
2. The bearing offers a more precise and rigid mount, less play for the gearbox mount.
3. It provides a better alignment of the tank forward motion vs. the gearbox forward momentum.

I have only a test sample of one on the German Leopard 2A6. All the above 3 points are tangible improvements, I paid $12 for the HL metal axle bearing on e-bay. It is one of the most cost effective upgrade I did.

I do not recommend putting a bearing on the plastic chassis over the axle drive. The plastic chassis is too flexible to provide the rigid mounting the bearing needs. An open air hole through the plastic chassis is the lowest friction design. Yes, it is high vibration.

With all respect to your background you are incorrect on many points. The bearings is optional for ONE REASON ONLY and that is to stabilize the drive shafts which helps reduces drive shaft wobbling. Reducing the wobble improves track retention. It does nothing else that you claim above. The reason for the metal housing was do to cracks forming in plastic housings and that ONLY happened on early production Leopard 2s of the 5.2/5.3 generation tanks. Most of the time it was clearly related to aftermarket heavy tracks and tanks running 390 motors. I went through four Leopards testing this.

As far as the "plastic" hulls overall they have proven to be rather strong and able to handle long periods of abuse when properly screwed together as this forms a unibody. Flex is largely caused by not using all the screws or by removing them and using magnets to hold the upper and lower hulls together. Flex is not something caused by the HL design it is caused by the end user modifying their tank. I have been testing and beating the hell out of HL tanks for more then a decade that is why HL asked me to consult with them from time to time and why they use my data to help make improvements in their tanks.

I could go on but I don't want to inadvertently violate my NDA with them.
Suffice to say I know a bit more on the subject then I let on. So much so I was one of the few people to see and have input on the Merkava back in 2019 long before any rumors even saw the light on day about it coming to market.